AWWA C651.pdf

AWWA Standard

SM

Disinfecting Water Mains

Effective date: Feb. 1, 2015.

First edition approved by AWWA Board of Directors Sept. 30, 1947.

This edition approved June 8, 2014.

Approved by American National Standards Institute Nov. 18, 2014.

Addendum incorporated Jan. 2020.

ANSI/AWWA C651-14

(Revision of ANSI/AWWA C651-05)

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AWWA Standard This document is an American Water Works Association (AWWA) standard. It is not a specification. AWWA standards describe minimum requirements and do not contain all of the engineering and administrative information normally contained in specifications. The AWWA standards usually contain options that must be evaluated by the user of the standard. Until each optional feature is specified by the user, the product or service is not fully defined. AWWA pub-lication of a standard does not constitute endorsement of any product or product type, nor does AWWA test, certify, or approve any product. The use of AWWA standards is entirely voluntary. This standard does not supersede or take precedence over or displace any applicable law, regulation, or codes of any governmental authority. AWWA standards are intended to represent a consensus of the water supply industry that the product described will provide satisfactory service. When AWWA revises or withdraws this standard, an official notice of action will be placed in the Official Notice section of Journal - American Water Works Association. The action becomes effective on the first day of the month fol-lowing the month of Journal - American Water Works Association publication of the official notice.

American National Standard An American National Standard implies a consensus of those substantially concerned with its scope and provisions.

An American National Standard is intended as a guide to aid the manufacturer, the consumer, and the general public.

The existence of an American National Standard does not in any respect preclude anyone, whether that person has ap-proved the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standard. American National Standards are subject to periodic review, and users are cautioned to obtain the latest editions. Producers of goods made in conformity with an American National Standard are encour-aged to state on their own responsibility in advertising and promotional materials or on tags or labels that the goods are produced in conformity with particular American National Standards.

Caution Notice: The American National Standards Institute (ANSI) approval date on the front cover of this standard indicates completion of the ANSI approval process. This American National Standard may be revised or withdrawn at any time. ANSI procedures require that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of ANSI approval. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute, 25 West 43rd Street, Fourth Floor, New York, NY 10036; 212.642.4900, or emailing info@ansi.org.

ISBN-13, print: 978-1-62576-046-3 eISBN-13, electronic: 978-1-61300-310-7

DOI: http://dx.doi.org/10.12999/AWWA.C651.14

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information or retrieval system, except in the form of brief excerpts or quotations for review purposes, without the written permission of the publisher.

Copyright © 2015 by American Water Works Association Printed in USA hours of work by your fellow water professionals.

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Committee Personnel

The AWWA Standards Committee on Disinfection of Facilities, which reviewed and approved this standard, had the following personnel at the time of approval:

Betsy Reilley, Chair

General Interest Members

Producer Members

User Members

* Liaison, nonvoting

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Contents All AWWA standards follow the general format indicated subsequently. Some variations from this format may be found in a particular standard.

SEC. PAGE SEC. PAGE

Foreword I Introduction..................................... vii

I.A Background...................................... vii

I.B History............................................. vii

I.C Acceptance....................................... vii

II Special Issues................................... viii

II.A Information on Application of This Standard............................ viii

III Use of This Standard......................... xi

III.A Purchaser Options and Alternatives................................. xi

III.B Modification to Standard................. xii

IV Major Revisions................................ xii

V Comments...................................... xiii

Standard

1 General

1.1 Scope

1.2 Purpose

1.3 Application

2 References

3 Definitions

4 Requirements

4.1 Forms of Chlorine for Disinfection

4.2 General Considerations for All

Methods of Chlorination

4.3 Tablet/Granule Method of

Chlorination

4.4 Continuous-Feed Method of

Chlorination

4.5 Slug Method of Chlorination

4.6 Spray Disinfection for Large

Transmission Lines

4.7 Basic Disinfection Procedure for

New Mains

4.8 Preventive and Corrective Measures

During New Construction

4.9 Final Flushing for New Mains

4.10 Final Connections to Existing

Mains

4.11 Disinfection Procedures When

Cutting Into or Repairing Existing Pipe

5 Verification

5.1 Bacteriological Tests

5.2 Optional Sampling and Testing

6 Delivery

Appenndixes A Chlorine Residual Testing

A.1 DPD Drop Dilution Method (for Field Test)

A.2 High-Range Chlorine Test Kits

B Chlorine Dosages

Figures 1 Suggested Temporary Flushing/Testing

Connection

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2 Suggested Combination Blowoff and Sampling Tap

Tables 1 Weight of Calcium Hypochlorite

Granules to Be Placed at Beginning of Main and at Each 500-ft (150-m) Interval

2 Number of 5-g Calcium Hypochlorite Tablets Required for Dose of 25 mg/L

3 Required Flow and Openings (Either Taps or Hydrants) to Flush Pipelines at 3.0 ft/sec (0.91 m/sec) (40 psi [276 kPa] Residual Pressure in Water Main)

4 Chlorine Required to Produce an Initial 25-mg/L Concentration in 100 ft (30.5 m) of Pipe by Diameter

B.1 Amounts of Chemicals Required to Produce Various Chlorine Concentrations in 100,000 gal (378.5 m3) of Water

B.2 Amounts of Chemicals Required to Produce Chlorine Concentrations of 200 mL in Various Volumes of Water

SEC. PAGE SEC. PAGE

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Foreword This foreword is for information only and is not a part of ANSI*/AWWA C651.

constructed potable water mains; mains that have been removed from service for planned repairs or for maintenance that exposes them to contamination; mains that have undergone emergency repairs because of physical failure; and mains that, under normal operation, continue to show the presence of coliform organisms. The disinfecting agents discussed in this standard are chlorine solutions that may be derived from liquid chlorine (Cl2), calcium hypochlorite (Ca(OCl)2), or sodium hypochlorite (NaOCl).

Combinations of free chlorine residual and contact time are provided. Chlorine dosage reference tables are provided as appendix B of this standard.

I.B. History. This standard was first approved on Sept. 30, 1947, by the AWWA Board of Directors and published as 7D.2-1948, A Procedure for Disinfecting Water Mains. Revisions were approved on Sept. 14, 1948; Mar. 6, 1953; May 27, 1954; June 2, 1968; and June 7, 1981. All were done under the designation ANSI/ AWWA C601, Standard for Disinfecting Water Mains. In 1986, the designation of the standard was changed to ANSI/AWWA C651, and the subsequent editions were approved on Jan. 26, 1986; June 18, 1992; June 20, 1999; and Jan. 16, 2005. This edition was approved on June 8, 2014.

I.C. Acceptance. In May 1985, the US Environmental Protection Agency (USEPA) entered into a cooperative agreement with a consortium led by NSF International (NSF) to develop voluntary third-party consensus standards and a certification program for direct and indirect drinking water additives. Other members of the original consortium included the Water Research Foundation (formerly AwwaRF) and the Conference of State Health and Environmental Managers (COSHEM). The American Water Works Association (AWWA) and the Association of State Drinking Water Administrators (ASDWA) joined later.

In the United States, authority to regulate products for use in, or in contact with, drinking water rests with individual states.† Local agencies may choose to impose requirements more stringent than those required by the state. To evaluate the health

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1. An advisory program formerly administered by USEPA, Office of Drinking Water, discontinued on Apr. 7, 1990.

Drinking Water Treatment Chemicals—Health Effects, and NSF/ANSI 61, Drinking Water System Components—Health Effects.

4. Other references, including AWWA standards, Food Chemicals Codex, Water Chemicals Codex,† and other standards considered appropriate by the state or local agency.

Various certification organizations may be involved in certifying products in accor-dance with NSF/ANSI 60. Individual states or local agencies have authority to accept or accredit certification organizations within their jurisdictions. Accreditation of certi-fication organizations may vary from jurisdiction to jurisdiction.

Annex A, “Toxicology Review and Evaluation Procedures,” to NSF/ANSI 60 does not stipulate a maximum allowable level (MAL) of a contaminant for substances not regulated by a USEPA final maximum contaminant level (MCL). The MALs of an unspecified list of “unregulated contaminants” are based on toxicity testing guidelines (noncarcinogens) and risk characterization methodology (carcinogens). Use of Annex A procedures may not always be identical, depending on the certifier.

ANSI/AWWA C651 does not address additives requirements. Thus, users of this standard should consult the appropriate state or local agency having jurisdiction in order to

for contact with, or treatment of, drinking water.

3. Determine current information on product certification.

disinfect a new main than one that has had emergency repairs in terms of access, sanitary control, and the time available for disinfection, sampling, and testing.

DC 20001.

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For a new main, there is typically more time available for disinfection and test-ing since there is no immediate demand from customers. Given the often significant amount of time and materials involved in a new water main project, careful disin-fection and testing of the main are reasonable and necessary to ensure public health protection.

Conditions for pipe repair projects vary tremendously in terms of the size of the repair, the sanitary conditions, and the time constraints resulting from immediate cus-tomer demands. It should be noted if the line is depressurized or opened to the envi-ronment prior to or during repair, the sanitary integrity of the pipe is compromised and it is critical to follow sanitary procedures throughout the repair—not just as it is being returned to service. Crews responsible for the repair of mains should be aware of the potential health hazards and be trained to carefully observe prescribed construction practices and disinfection procedures.

Because of the differences between initial installation and repair, the disinfec-tion requirements for each situation are also different. The installation of new mains requires that two sets of samples for coliform analysis are collected at least 16 hr apart, or two sets collected 15 min apart after at least a 16-hr rest period. For repaired mains that are depressurized and/or wholly or partially dewatered, one set of samples may be required, and depending on the sanitary conditions, the line may be returned to service prior to the completion of bacteriological testing. For repaired mains that are main-tained under pressurized conditions at all times, bacteriological testing is not required

When required, samples are now specified to be collected at least 16 hr apart, or 15 min apart after a 16-hr rest period. The purpose of this change is to consider the balance between public health, improved test methods, and timely work completion.

This timing is sufficient to allow bacterial regrowth within the line if there was a con-tamination problem and provides more flexibility in the scheduling of various work activities.

Bacteriological testing in accordance with Sec. 5.1 is used to verify the absence of coli-form organisms and is generally accepted as verification that disinfection of the pipeline has been accomplished; and following sanitary practices for handling and installation of pipe, valves, fittings, and accessories, coupled with adequate flushing of the line before disinfection, is necessary to ensure the disinfected pipeline will be ready for connection to the water system. Failure to pass the bacteriological test requires that the flushing or disinfection process be repeated. It must be remembered that the final water quality test is not the primary means for certifying the sanitary condition of a main. The sanitary

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Four methods of disinfecting newly constructed water mains are described in this standard: the tablet method, the continuous-feed method, the slug method, and the spray method. The utility should decide which of these methods is most suitable for a given situation. Factors to consider when choosing a method should include the length and diameter of the main, type of joints present, availability of materials, equipment required for disinfection, training of the personnel who will perform the disinfection, and safety concerns. For example, if gas chlorination is the chosen chemical when either continuous-feed or slug methods are being used, use only properly designed and constructed equipment; makeshift equipment is not acceptable when liquid chlorine (gas) cylinders are used.

Thorough consideration should be given to the impact of highly chlorinated water flushed into the environment. If there is any question that damage may be caused by chlorinated-waste discharge (to fish life, plant life, physical installations, or other downstream water uses of any type), then an adequate amount of reducing agent should be applied to water being disposed of in order to thoroughly neutralize the chlorine residual remaining in the water.

The tablet method cannot be used unless the main can be kept clean and dry. It cannot be used in large-diameter mains if it is necessary for a worker to enter the main to grout joints or perform inspection because the tablets may release toxic fumes after exposure to moist air. When using the tablet method, the chlorine concentration is not uniform throughout the main because the hypochlorite solution is dense and tends to concentrate at the bottom of the pipe. The use of the tablet method precludes prelimi-nary flushing. The tablet method is convenient to use in mains having diameters up to 24 in. (600 mm), and it requires no special equipment.

The continuous-feed method is suitable for general application. Preliminary flush-ing removes light particulates from the main but not from the pipe-joint spaces. The chlorine concentration is uniform throughout the main.

The slug method is suitable for use in large-diameter mains where the volume of water makes the continuous-feed method impractical and difficult to achieve for short attachments. The slug method results in appreciable savings of chemicals used to disinfect long large-diameter mains. Also, this method reduces the volume of heavily chlorinated water to be flushed to waste.

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The spray method is suitable for use in large-diameter transmission lines where spray equipment can be used to disinfect all surfaces of the pipe. This method reduces the volume of heavily chlorinated water to be flushed to waste.

The purpose of all four chlorination methods is to disinfect water lines, resulting in an absence of coliforms as confirmed by laboratory analysis. As noted above, the four methods attempt to provide flexibility in responding to specific situations. The tablet and continuous-feed methods both have initial chlorine concentrations of 25 mg/L and a minimum contact time of 24 hr. Because the tablet method cannot be flushed and cleaned prior to disinfection, the required free chlorine residual must be detectable (≥0.2 mg/L) after 24 hr. Because the continuous-feed method can be used to flush particles, a higher free chlorine residual of 10 mg/L is required after 24 hr. To meet the needs of situations requiring reduced contact times, the slug method allows only a 3-hr contact time but requires a 100-mg/L initial chlorine dosage. For larger transmis-sion lines, spray disinfection using 200 mg/L free chlorine may be a suitable option, minimizing discharges of highly chlorinated water. While the contact times of the methods may not be identical, the end result, absence of coliforms, is the same for all four methods.

Disinfectants other than chlorine may be appropriate to use. Although this stan-dard describes only the use of liquid chlorine (gas), sodium hypochlorite solutions, and calcium hypochlorite, the applicability of other disinfectants should be evaluated.

Ozone and chemical cleaners have been used, and these warrant further investiga-tion. Whichever disinfectant or method is selected, approval from the local regulatory agency may be required.

III. Use of This Standard. It is the responsibility of the user of an AWWA standard to determine that the products described in that standard are suitable for use in the particular application being considered.

III.A. Purchaser Options and Alternatives. This standard is written as though the disinfection work will be performed by the purchaser’s personnel. Where the work is to be performed using a separate contract or as part of a contract for installing mains,* appropriate provisions should be included in the purchase documents to ensure that the constructor is specifically instructed as to its responsibilities. The following information should be provided by the purchaser.

* Refer to other AWWA standards and manuals for design criteria and installation procedures for vari-ous pipe materials.

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1. Standard used— that is, ANSI/AWWA C651, Standard for Disinfection of Water Mains, of latest revision.

that are to be included in the purchase documents.

4. Whether compliance with NSF/ANSI 60, Drinking Water Chemicals—

Health Effects, is required.

5. Whether compliance with NSF/ANSI 61, Drinking Water System

Components—Health Effects, is required.

4.4.2, 4.9.1, and 4.9.2).

10. Responsibility for tapping existing mains and connections to new mains

(Sec. 4.4.3[1], 4.4.3[2], and 4.10).

11. The number and frequency of samples for bacteriological tests (Sec. 5.1.1, 5.1.2, and 5.2).

12. Method of taking samples (Sec. 5.1.3).

III.B. Modification to Standard. Any modification of the provisions, definitions, or terminology in this standard must be provided by the purchaser.

IV. Major Revisions. Major revisions made to the standard in this edition include the following:

1. Clarified differences in the requirements between new and repaired mains (foreword II.A, Sec. 1.1, and 4.11).

2. Changed the requirement for bacteriological sampling in new mains from two sets of samples 24 hr apart to add two options for two sets of samples: Option A samples are 16 hr apart, and Option B samples are 15 min apart after a 16-hr rest period (foreword II.A and Sec. 5.1).

3. The flushing rate of 2.5 ft/sec has been increased to 3.0 ft/sec for a scour flush based on testing performed under Water Research Foundation Project No. 4307, which indicates the threshold velocity of 2.5 to 3.0 ft/sec for successful flushing (2.5- to 3.0-log removal) of sand particles. Since this is a threshold velocity, 3.0 ft/sec was chosen for the standard (Sec. 4.4.2 and Table 3).

4. Added spray disinfection method for large transmission mains (Sec. 4.6).

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5. Appendix C has been deleted, and instead, a reference to ANSI/AWWA C655 is made for dechlorination (Sec. 4.7 and 4.9.2).

6. Developed a rationale for evaluating risk during pipe repairs and the level of disinfection and sampling needed under those conditions (Sec. 4.11).

V. Comments. If you have any comments or questions about this standard, please call the AWWA Engineering and Technical Services at 303.794.7711, FAX at 303.795.7603; write to the group at 6666 West Quincy Avenue, Denver, CO 80235- 3098; or email the group at standards@awwa.org.

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AWWA Standard®

Disinfecting Water Mains

SECTION 1: GENERAL

Sec. 1.1 Scope This standard describes essential procedures for the disinfection of new and repaired potable water mains. New water mains shall be disinfected before they are placed in service. Water mains taken out of service for inspection, repair, or other activities may or may not require disinfection and sampling, depending on the risk of contamination. This standard described the process for evaluating the risk under different conditions. This standard is meant to be used for water mains within public water systems and is not intended for premise plumbing systems in buildings. Premise plumbing components in building use a wide variety of materi-als, including some that may not be compatible with the chlorine concentrations in this standard.

Sec. 1.2 Purpose The purpose of this standard is to define the minimum requirements for the disinfection of water mains, including the preparation of water mains, application of chlorine, and sampling and testing for the presence of coliform bacteria.

Sec. 1.3 Application This standard can be referenced in the purchase documents for the disinfection of water mains and can be used as a guide for the preparation of water mains, applica-tion of chlorine, and sampling and testing for the presence of coliform bacteria. The stipulations of this standard apply when this document has been referenced and only to the disinfection of water mains.

ANSI/AWWA C651-14

(Revision of ANSI/AWWA C651-05)

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2 AWWA C651-14

SECTION 2: REFERENCES

This standard references the following documents. In their latest editions, they form a part of this standard to the extent specified within the standard. In any case of conflict, the requirements of this standard shall prevail.

ANSI*/AWWA B300—Hypochlorites.

ANSI/AWWA B301—Liquid Chlorine.

ANSI/AWWA C652—Disinfection of Water Storage Facilities.

ANSI/AWWA C655—Field Dechlorination.

APHA,† AWWA, and WEF.‡ Standard Methods for the Examination of Water and Wastewater.

AWWA Manual M12, Simplified Procedures for Water Examination.

NSF/ANSI 61—Drinking Water System Components–Health Effects.

SECTION 3: DEFINITIONS

The following definitions shall apply in this standard:

1. Available chlorine: A measure of the amount of chlorine in chlorinated lime, hypochlorite compounds, chloramines, and other materials that are used for disinfection compared with the amount in elemental (liquid or gaseous) chlorine.

2. Chlorine, combined: The amount of chlorine combined with ammonia (NH3) or other compounds in water.

3. Chlorine, free: Also called free available chlorine, the amount of chlo-rine available as dissolved gas (Cl2), hypochlorous acid (HOCl), and hypochlorite (OCl–) that is not combined with ammonia (NH3) or other compounds in water that is available for disinfection.

4. Chlorine residual: Concentration of chlorine species present in water after the oxidant demand has been satisfied.

5. Chlorine, total: A combination of free chlorine, combined chlorine, and organochlorine species.

6. Constructor: The party that provides the work and materials for place-ment or installation.

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DISINFECTING WATER MAINS 3

7. Liquid chlorine (gas): the commercially available form of liquefied elemental chlorine gas. (The term liquid chlorine is sometimes used to describe a hypochlorite solution. This use of the term is discouraged. See ANSI/AWWA B300, Hypochlorites.)

8. Manufacturer: The party that manufactures, fabricates, or produces materials or products.

9. Purchaser: The person, company, or organization that purchases any materials or work to be performed.

10. Supplier: The party that supplies material or services. A supplier may or may not be the manufacturer.

11. Organochlorine: Any organic compound containing chlorine as a con-stituent. Organochlorine compounds can form when chlorine reacts with organic substances.

SECTION 4: REQUIREMENTS

Materials shall comply with the requirements of the Safe Drinking Water Act and other federal regulations for potable water, wastewater, and reclaimed water systems as applicable.

Sec. 4.1 Forms of Chlorine for Disinfection The forms of chlorine that may be used in the water main disinfection opera-tions are liquid chlorine (gas), sodium hypochlorite solution, and calcium hypo-chlorite granules or tablets.

4.1.1 Liquid chlorine (gas). Liquid chlorine (gas) conforming to ANSI/ AWWA B301 contains 100 percent available chlorine and is packaged in steel containers usually of 100-lb, 150-lb, or 1-ton (45.4-kg, 68.0-kg, or 907.2-kg) net chlorine weight. Liquid chlorine (gas) shall be used only (1) in combination with appropriate gas-flow chlorinators and ejectors to provide a controlled high-concen-tration solution feed to the water to be chlorinated; (2) under the direct supervision of someone familiar with the biological, chemical, and physical properties of liquid chlorine (gas) and who is trained and equipped to handle any emergency that may arise; and (3) when appropriate safety practices are observed to protect working personnel and the public. Makeshift equipment is not acceptable when liquid chlo-rine (gas) cylinders are used.

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4 AWWA C651-14

4.1.2 Sodium hypochlorite. Sodium hypochlorite conforming to ANSI/ AWWA B300 is available in liquid form in glass, rubber-lined, or plastic contain-ers typically ranging in size from 1 qt (0.95 L) to 5 gal (18.92 L). Containers of 30 gal (113.6 L) or larger may be available in some areas. Sodium hypochlorite contains approximately 5 percent to 15 percent available chlorine, and the storage conditions and time must be controlled to minimize its deterioration. (Available chlorine is expressed as a percent of weight when the concentration is 5 percent or less, and usually as a percent of volume for higher concentrations. Percent × 10 = grams of available chlorine per liter of hypochlorite.)

4.1.3 Calcium hypochlorite. Calcium hypochlorite conforming to ANSI/ AWWA B300 is available in granular form or in 5-g tablets and must contain approximately 65 percent available chlorine by weight. The material should be stored in a cool, dry, and dark environment to minimize its deterioration.

Caution: Tablets dissolve in approximately 7 hr and must be given adequate contact time. Do not use calcium hypochlorite intended for swimming pool disin-fection, as this material has been sequestered and is extremely difficult to eliminate from the pipe after the desired contact time has been achieved.

Sec. 4.2 General Considerations for All Methods of Chlorination

4.2.1 General. Four methods of chlorination are explained in this sec-tion: tablet, continuous feed, slug, and spray. The tablet method gives an initial chlorine dose of 25 mg/L; the continuous-feed method gives a 24-hr chlorine residual of not less than 10 mg/L; the slug method gives a 3-hr exposure of not less than 50 mg/L free chlorine; and the spray method gives a 30-min exposure of not less than 200 mg/L free chlorine. Caution should be used with highly chlorinated water when conducting hydrostatic pressure testing and with high-volume flushing of water.

4.2.2 Flushing. Potable water shall be used for disinfection, hydrostatic pressure testing, and flushing. Drainage should take place away from the construc-tion or work area. Adequate drainage must be provided during flushing. If appli-cable, the valve(s) isolating the main from existing system should be locked out and tagged out to prevent unintentional release of the elevated chlorine residual water used for disinfection.

4.2.3 Dechlorination. When dechlorination is required, it is recom-mended that any high-velocity flushing be completed prior to disinfection. Dechlo-rination equipment may not be capable of handling high flows with high levels of chlorine.

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DISINFECTING WATER MAINS 5

Sec. 4.3 Tablet/Granule Method of Chlorination

4.3.1 Tablet method. The tablet method consists of placing calcium hypo-chlorite granules or tablets in the water main during installation and then filling the main with potable water to create a chlorine solution. This method may be used only if the pipes and appurtenances are kept clean and dry during construction.

Warning: This procedure must not be used on solvent-welded plastic or on screwed-joint steel pipe because of the danger of fire or explosion from the reaction of the joint compounds with the calcium hypochlorite.

4.3.2 Placement of calcium hypochlorite granules during construction. Cal-cium hypochlorite granules shall be placed at the upstream end of the first section of pipe, at the upstream end of each branch main, and at 500-ft (150-m) intervals.

The quantity of granules at each location shall be as shown in Table 1.

4.3.3 Placement of calcium hypochlorite tablets during construction. Cal-cium hypochlorite tablets (5-grams) shall be placed in the upstream end of each section of pipe to be disinfected, including branch lines. Also, at least one tablet shall be placed in each hydrant branch and in other appurtenances. The number of 5-g tablets required for each pipe section shall be 0.0012 d 2L rounded to the next higher integer, where d is the inside pipe diameter, in inches, and L is the length of the pipe section, in feet. Table 2 shows the number of tablets required for commonly used sizes of pipe. Calcium hypochlorite tablets shall be attached by an adhesive meeting the requirements of NSF/ANSI 61. There shall be adhesive only on the broadside of the tablet attached to the surface of the pipe. Attach tablets inside and at the top of the main. If the tablets are attached before the pipe section is placed in

Table 1 Weight of calcium hypochlorite granules to be placed at beginning of main and at each 500-ft (150-m) interval

Pipe Diameter (d) Calcium Hypochlorite Granules

in. (mm) oz (g)

4 (100) 1.7 (48) 6 (150) 3.8 (108) 8 (200) 6.7 (190)

10 (250) 10.5 (298) 12 (300) 15.1 (428)

14 and larger (350 and larger) D2 × 15.1 D2 × 428

Where D is the inside pipe diameter, in feet D = d/12

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6 AWWA C651-14

the trench, their positions shall be marked on the pipe exterior to indicate that the pipe has been installed with the tablets at the top.

4.3.4 Filling and contact time. When installation has been completed, the main shall be filled with water such that the full pipe velocity is no greater than 1 ft/sec (0.3 m/sec). Fill rate must be carefully controlled to ensure tablets do not come loose from pipe. Precautions shall be taken to ensure that air pockets are eliminated. As an optional procedure, if required by the purchaser, water used to fill the new main shall be supplied through a temporary connection that shall include an appropriate cross-connection control device, consistent with the degree of hazard, for backflow protection of the active distribution system (see Figure 1).

The chlorinated water shall remain in the pipe for at least 24 hr. If the water temperature is less than 41°F (5°C), the water shall remain in the pipe for at least 48 hr. A detectable free chlorine residual (≥0.2 mg/L) shall be found at each sampling point after the 24- or 48-hr period.

Sec. 4.4 Continuous-Feed Method of Chlorination

4.4.1 Continuous-feed method. The continuous-feed method consists of completely filling the main with potable water, removing air pockets, then flush-ing the completed main to remove particulates, and refilling the main with potable water that has been chlorinated to 25 mg/L. After a 24-hr holding period in the main there shall be a free chlorine residual of not less than 10 mg/L.

4.4.2 Preliminary flushing. Before the main is chlorinated, it shall be filled with potable water to eliminate air pockets and flushed to remove particulates. The flushing velocity in the main shall not be less than 3.0 ft/sec (0.91 m/sec) unless

Table 2 Number of 5-g calcium hypochlorite tablets required for dose of 25 mg/L*

Length of Pipe Section, ft (m)

Pipe Diameter 13 (4.0) or less 18 (5.5) 20 (6.1) 30 (9.1) 40 (12.2)

in. (mm) Number of 5-g Calcium Hypochlorite Tablets

4 (100) 1 1 1 1 1 6 (150) 1 1 1 2 2 8 (200) 1 2 2 3 4

10 (250) 2 3 3 4 5 12 (300) 3 4 4 6 7 16 (400) 4 6 7 10 13

*Based on 3.25-g available chlorine per tablet

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DISINFECTING WATER MAINS 7

2½-in. Control Valve

Cross-Connection Control Device

Supply Hose*

New Water Main Temporary Cap or Plug See Figure 2 for detail on suggested blowoff and sampling tap.

Control Valve

Smooth, Unthreaded Sampling Faucet

Discharge/flushing Dechlorination

Note: Figure 1 applies to pipes with diameters 4 in. (100 mm) through 12 in. (300 mm). Larger sizes must be handled on a case-by-case basis.

*�Clean potable-water hose only. Size and number of taps per Table 3. This hose must be removed during the hydrostatic pressure test.

Figure 1 Suggested temporary flushing/testing connection

Table 3 Required flow and openings (either taps or hydrants) to flush pipelines at 3.0 ft/sec (0.91 m/sec) (40 psi [276 kPa] residual pressure in water main)*

Pipe Diameter

Flow Required to Produce 3.0 ft/sec

(approx.) Velocity in Main

Size of Tap Used, in. (mm)

Number of Hydrant Outlets1 (25) 1½ (38) 2 (51)

in. (mm) gpm (L/sec) Number of Taps Required on Pipe† 2½-in.

(64-mm) 4½-in.

(114 mm)

4 (100) 120 (7.4) 1 — — 1 1 6 (150) 260 (16.7) — 1 — 1 1 8 (200) 470 (29.7) — 2 — 1 1

10 (250) 730 (46.3) — 3 2 1 1 12 (300) 1,060 (66.7) — — 3 2 1 16 (400) 1,880 (118.6) — — 5 2 1

*With a 40-psi (276-kPa) pressure in the main with the hydrant flowing to atmosphere, a 2½-in. (64-mm) hydrant outlet will discharge approximately 1,000 gpm (63.1 L/sec); and a 4½-in. (114-mm) hydrant outlet will discharge approximately 2,500 gpm (160 L/sec).

†Number of taps on pipe based on 3.0-ft/sec discharge through 5 ft (1.5 m) of galvanized iron (GI) pipe with one 90° elbow.

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8 AWWA C651-14

the purchaser determines that conditions do not permit the required flow to be dis-charged to waste. Table 3 shows the rates of flow required to produce a velocity of

3.0 ft/sec (0.91 m/sec) in commonly used sizes of pipe. (Note: flushing is no sub-stitute for preventive measures during construction. Certain contaminants, such as caked deposits, resist flushing at any feasible velocity, and pigging of the main, or other suitable method acceptable to the purchaser, may be required.) Where such flow rates are not possible, flushing at the maximum expected flow rate for the line for 2–3 volumes may be acceptable. For larger mains, pigging (or other suitable method acceptable to the purchaser) is an option in place of high velocity flushing.

For 24-in. (600-mm) or larger diameter mains, an acceptable alternative to flushing is to broom-sweep the main, carefully removing sweepings prior to filling and chlorinating the main. Warning: OSHA requirements for confined space need to be addressed before entering a pipeline.

4.4.3 Procedure for chlorinating the main.

1. Potable water may be supplied from a temporary backflow-protected con-nection to the existing distribution system or other supply source approved by the purchaser. The cross-connection control device shall be consistent with the degree of hazard for backflow protection of the active distribution system (see Figure 1).

The flow shall be at a constant, measured rate into the newly installed water main.

In the absence of a meter, the rate may be approximated using a Pitot gauge in the discharge, measuring the time to fill a container of known volume, or measuring the trajectory of the discharge and using the formula shown in Figure 2. The main should undergo hydrostatic testing prior to disinfection.

2. At a point not more than 10 ft (3 m) downstream from the beginning of the new main, water entering the new main shall receive a dose of chlorine fed at a constant rate such that the water will have not less than 25 mg/L free chlorine. To ensure that an appropriate concentration is achieved, the free chlorine concentra-tion shall be measured at regular time intervals in accordance with the procedures described in Standard Methods for the Examination of Water and Wastewater or AWWA Manual M12, or using appropriate chlorine test kit (see appendix A).

Table 4 gives the amount of chlorine required for each 100 ft (30.5 m) of pipe for various pipe diameters. Solutions with a minimum 1 percent chlorine concen-tration may be prepared with sodium hypochlorite or calcium hypochlorite. The latter solution requires 1 lb (454 g) of calcium hypochlorite in 8 gal (30.3 L) of water.

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DISINFECTING WATER MAINS 9

3. Chlorine application shall not cease until the entire main is filled with chlorinated water. The chlorinated water shall be retained in the main for at least 24 hr, during which time valves and hydrants in the treated section shall be oper-ated to ensure disinfection of the appurtenances. At the end of this 24-hr period, the treated water in all portions of the main shall have a residual of not less than 10 mg/L of free chlorine.

4. Direct-feed chlorinators, which operate solely from gas pressure in a chlo-rine cylinder, shall not be used for the application of liquid chlorine (gas). (The

Smooth, Unthreaded ½-in. Hose Bib for Bacteria Samples

12-in. Minimum

Control Valve

18-in.

Minimum

Sx

S y

-in

. M in im um

Formula for Estimating Rate of Discharge

Where:

Q d d, Sx, Sy

Discharge in gallons per minute Inside diameter of all flushing pipe Measured in inches

Q =

2.83 d 2Sx

Sy√ d

Note: This figure applies to pipes up to and including 8-in. (200-mm) diameter.

Figure 2 Suggested combination blowoff and sampling tap

Table 4 Chlorine required to produce an initial 25-mg/L concentration in 100 ft (30.5 m) of pipe by diameter

Pipe Diameter 100% Chlorine 1% Chlorine Solution

in. (mm) lb (g) gal (L)

4 (100) 0.013 (5.9) 0.16 (0.6) 6 (150) 0.030 (13.6) 0.36 (1.4) 8 (200) 0.054 (24.5) 0.65 (2.5)

10 (250) 0.085 (38.6) 1.02 (3.9) 12 (300) 0.120 (54.4) 1.44 (5.4) 16 (400) 0.217 (98.4) 2.60 (9.8)

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10 AWWA C651-14

danger of using direct-feed chlorinators is that water pressure in the main can exceed gas pressure in the chlorine cylinder. This allows backflow of water into the cylinder, resulting in severe cylinder corrosion and the escape of chlorine gas.)

The preferred equipment for applying liquid chlorine (gas) is a solution-feed, vacuum-operated chlorinator and a booster pump. The vacuum-operated chlori-nator mixes the chlorine gas in solution water; the booster pump then injects the chlorine solution into the main to be disinfected. Hypochlorite solutions may be applied to the water main with a chemical-feed pump designed for feeding chlorine solutions. Feed lines shall be made of material capable of withstanding the corro-sion caused by the concentrated chlorine solutions and the maximum pressures that may be created by the pumps. All connections shall be checked for tightness before the solution is applied to the main.

Sec. 4.5 Slug Method of Chlorination

4.5.1 Slug method. The slug method consists of completely filling the main to eliminate air pockets; flushing the main to remove particulates; then slowly flowing through the main a slug of water dosed with chlorine to a concen-tration of 100 mg/L. The slow rate of flow ensures that all parts of the main and its appurtenances will be exposed to the highly chlorinated water for a period of not less than 3 hr.

4.5.2 Preliminary flushing. Same as Sec. 4.4.2.

4.5.3 Procedure for chlorinating the main.

1. Potable water may be supplied from a temporary backflow-protected con-nection to the existing distribution system or other supply source approved by the purchaser. The cross-connection control device shall be consistent with the degree of hazard for backflow protection of the active distribution system (see Figure 1).

The flow shall be at a constant, measured rate into the newly installed water main.

In the absence of a meter, the rate may be approximated using a Pitot gauge in the discharge, measuring the time to fill a container of known volume, or measuring the trajectory of the discharge and using the formula shown in Figure 2. The main should undergo hydrostatic testing prior to disinfection.

2. At a point not more than 10 ft (3 m) downstream from the beginning of the new main, water entering the new main shall receive a dose of chlorine fed at a constant rate such that the water will have not less than 100 mg/L free chlorine.

To ensure that this concentration is achieved, the free chlorine concentration shall be measured at regular time intervals sufficient to guide the completion of the suc-cessful loading of the…