This article is about Water Main Testing and Disinfection Procedures, methods, awwa c651 disinfecting water mains pdf, water main chlorination calculations, water main swabbing procedure, disinfection procedure for water distribution lines, water main chlorination equipment, water main disinfection calculator, disinfecting potable water piping, chlorination of water mains in commercial buildings, plants and refinery projects related to Plumbing Engineering System as per international codes and standards.
New Water Main Testing and Disinfection Procedure & Guidelines
General Requirements
- Potable Water (Raw/Utility and Drinking Water) lines as covered by SAES-S-040 shall be disinfected before they are placed in service.
- For Thermoplastic and RTR Piping, the hypochlorites to be use shall be in solution form.
Tablet Method
- Note: May be used only if the pipes and appurtenances are kept clean and dry during construction”
- During construction, calcium 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 intervals. The quantity of granules shall be as shown in Table 7. See attached below
- 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. (SASC-S-01 Para 9.6.1)” - During construction, 5 gram (0.2 ounce) calcium hypochlorite tablets shall be placed in each section of pipe and also one such tablet shall be placed in each hydrant, hydrant branch, and other appurtenance. The number of tablets required for each pipe section shall comply with guidelines listed in Table 8. See attached (SASC-S-01 Para 9.6.2)”
- The tablets shall be attached by an approved adhesive. There shall be no adhesive on the tablet except on the broad side attached to the surface of the pipe. Attach all the tablets inside and at the top of the main, with approximately equal numbers of tablets at each end of each pipe length. If the tablets are attached before the pipe section is placed in the trench, the top of the pipe shall be marked for easy installation.
- When installation has been completed, the main shall be filled with water at a rate such that water within the main will flow at a velocity no greater than 30.5 centimeters per second (1 foot per second). Precautions shall be taken to assure that air pockets are eliminated. This water shall remain in the pipe for at least 24 hours.
- The tablet method shall yield a chlorine residual of at least 25 milligrams per liter (25 parts per million) 24 hours after the time at which the main was filled with water. Valves shall be positioned so that the strong chlorine solution in the treated main will not flow into water mains in active service.
Continues Feed Method
- All connections shall be checked for tightness before the solution is applied to the main.
- If deemed necessary by Saudi Aramco’s EPD, calcium hypochlorite granules shall be placed in pipe sections as specified in item No. A1
- Before being chlorinated, the main shall be filled to eliminate air pockets and shall be flushed to remove particulates. The flushing velocity in the main shall not be less than 76 centimetersper second (2.5 feet per second) unless Saudi Aramco’s EPD determines that conditions do not permit the required flow to be discharged to waste. In mains of 61 centimeters (24 inches) or larger diameter, an acceptable alternative to flushing is to broom-sweep the main, carefully removing all sweepings prior to chlorinating the main.
- Water from the existing distribution system or other approved source of supply shall be made to flow at a constant, measured rate into the newly laid water main. In the absence of a meter, the rate may be approximated by methods such as placing a Pitot gauge in the discharge or measuring the time to fill a container of known volume.
- At a point not more than 3 meters (10 feet) 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 milligrams per liter (25 parts per million) free chlorine. The chlorine concentration shall be measured at regular intervals. (SASC-S-01 Para 9.7.3.2)
- During the application of chlorine, valves shall be positioned so that the strong chlorine solution in the main being treated will not flow into water mains in active service. Chlorine application shall not cease until the entire main is filled with superchlorinated water. The chlorinated water shall be retained in the main for at least 24 hours, during which time all valves and hydrants in the treated section shall be operated to ensure disinfection of the appurtenances. At the end of this 24-hour period, the treated water in all portions of the main shall have a residual of not less than 10 milligrams per liter (10 parts per million) free chlorine. (SASC-S-01 Para 9.7.3.3)
- For applying liquid chlorine USE solution- feed, vacuum-operated chlorinator and a booster pump. Hypochlorite solutions may also be applied to the water main with a gasoline or electrically powered chemical- feed pump designed for feeding chlorine solutions. Feed lines shall be of such materials and strength as to safely withstand the corrosion caused by the concentrated chlorine solutions and the maximum pressures that may be created by the pumps.
Note: Direct-feed chlorinators, which operate solely from gas pressure in the chlorine cylinder, shall not be used for application of liquid chlorine”
Slug Method
- Preliminary flushing, same as item B3 of this SAIC.
- Placing calcium hypochlorite granules, same as item A1 of this SAIC.
- Same as Item B4 of this SAIC, concerning the requirement during the application of chlorine.
- At a point not more than 3 meters (10 feet) 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 milligrams per liter free chlorine. To ensure that this concentration is provided, the chlorine concentration shall be measured at regular intervals.
- Chlorine shall be applied continuously and for a sufficient period to develop a solid column, or “slug,” of chlorinated water that will, as it moves through the main, expose all interior surfaces to a free chlorine concentration of approximately 100 milligrams per liter (100 parts per million) for at least 3 hours.
- The free chlorine residual shall be measured in the slug as it moves through the main. If at any time it drops below 50 milligrams per liter (50 parts per million), the flow shall be stopped, chlorination equipment shall be relocated at the head of the slug, and, as flow is resumed, chlorine shall be applied to restore the free chlorine in the slug to not less than 100 milligrams per liter (100 parts per million)
- As the cholirinated water flows past fittings and valves, related valves and hydrants shall be operated sop as to disinfect appurtenances and pipe branches.
General (Applicable to all three methods)
- “After the applicable retention period the superchlorinated water shall be flushed from the main until chlorine measurements show that the concentration in the water leaving the main is not greater than 3 milligrams per liter (3 parts per million).
NOTE: In the planning stage of the project, the potential environmental impacts associated with the disposal of the superchlorinated water shall be considered and appropriate plans shall be developed to properly mitigate adverse effects. The disposal plan shall be developed in consultation with EPD.”
Bacteriological tests:
- After final flushing and before the water main is placed in service, a sample or samples shall be collected for bacteriological analysis. Samples shall be tested to verify the absence of coliform organisms (a heterotrophic plate count [HPC] of less than 500 CFU/ml may also be required by Saudi Aramco’s EPD). At least one sample shall be collected from the end of a new main and one from each branch. If the main is extremely long, samples shall be collected along the length of the line as well as at its end.
- If, during construction, trench water has entered the main, or if in the opinion of Saudi Aramco’s EPD, excessive quantities of dirt or debris have entered the main, bacteriological samples shall be taken at intervals of approximately 61 meters (200 feet) and shall be identified by location. Samples shall be taken of water that has stood in the main for at least 16 hours after final flushing has been completed.
- Samples for bacteriological analysis shall be collected in sterile bottles treated with sodium thiosulfate. No hose or fire hydrant shall be used in collection of samples. A corporation cock may be installed in the main with a copper-tube gooseneck assembly. After samples have been collected, the gooseneck assembly may be removed and retained for future use.
- If the initial disinfection fails to produce satisfactory bacteriological samples, the main may be re-flushed and shall be re-sampled. If check samples show the presence of coliform organisms, then the main shall be re-chlorinated by the continuous-feed or slug method of chlorination until satisfactory results are obtained. High velocities in the existing system, resulting from flushing the new main, may disturb sediment that has accumulated in the existing mains. When check samples are taken, it is recommended that water entering the new main also be sampled.
Note: All samples returned from the laboratory that state confluent bacterial growth/too numerous to count (CBG/TNTC) or too numerous to count/no coliform (TNTC/NC) shall be considered invalid and must be re-sampled at the next available opportunity.
Guide to Preparation of Chlorine Solution Using 15% Hypochlorite Liquid as Chlorine Source
Grams/Ounces of Calcium Hypochlorite Granules to be placed at Beginning of Main and at each 500 ft interval
