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1 Sometimes, a pipeline is to be taken across a wall or slab. In such a case, always use a sleeve for the pipe for the thickness of the wall or slab. Keep the diameter of the sleeve sufficiently large to easily pass the pipeline through it. For example, for ½” pipeline, use 1” dia sleeve. Never allow a bend in the sleeve. Let sleeve be also from a good quality IS 1239 pipe so that it doesn’t rust with time. 2 Final water supply network should always be tested under pressure to check any leakages. This testing should be done before filling the chases in masonry walls and finishing them with plaster. Once the water supply lines have been erected in position and all pipe grids have been completed, ask the plumbing contractor to test the system under pressure and show it to be leak proof. Don’t allow concealing of pipes unless pressure testing has been done. Sometimes, plaster work is taken up in parallel in the bathrooms or kitchen and wall chases cut to lay the pipes are filled and finished after erection of pipes. Tell the plumber in advance that this is not to be done unless the water supply network has been tested and made leak proof. 3 For pressure testing of water supply lines, a pump is used to pump-in water at a pressure of 200 feet of water or more. A gauge erected on the pump gives the water pressure reading. Check this gauge to have zero error or its initial reading should be noted. If possible, see that it has been calibrated by a good test house. Ask to maintain water pressure in the pipes for one hour at least. Thereafter, with the pressure maintained, check that no pipe or joint should have even the slightest leakage. 4 Many queries have been received to throw light on use of PVC pipes also for water supply purpose. The trend of using PVC pipes seems to be growing. Of course, PVC pipes are cheaper than GI pipes but their fittings are costlier. Specially, the PVC fittings with brass couplers inserted in them are costlier. Overall, PVC water supply system proves 10 to 15% cheaper than B class GI pipe system. 5 If you are choosing u PVC pipes for water supply, choose a reputed brand. Here u means unplasticized. Prince, Supreme and Finolex are some of the reputed brands. Look for ISI mark. There are many kinds of PVC pipes available in the market for different purposes. So be careful and choose one manufactured for potable (drinking) water supply purpose. Only such PVC pipes that carry IS 4985 are suitable for drinking water supply. 6 Avoid use of PVC pipes for carrying hot water. Though the PVC pipe manufacturers claim that PP-R (Polypropylene Random) pipes now produced by them are fully suitable for carrying hot water having temperature up to 600C, prefer to use GI pipe from the geyser or solar water heater to the water outlets. If a combination of PVC pipes for cold water and GI pipes for hot water is used, don’t run the two lines too close to each other. For all vertical PVC pipes, provide enough supports at 2 feet intervals. 7 PVC pipes are jointed by using solvent cement, by threading, by using rubber gaskets or by heat welding and compression. Generally, heat welding and compression is suitable in LDPE, HDPE and PP-R pipes while solvent cement, threading and rubber gaskets are used for other PVC pipes. When solvent cement is used, the joint becomes unbreakable. Whenever solvent cement is used for the pipe joints, choose only that type and brand of it which is recommended by the manufacturer of the pipe selected by you. 8 Whenever PP-R pipes are chosen for water supply, take care that these are welded well so that no leakage of joints occurs. For heat welding of PP-R pipes, a small welding machine that can be plugged to 230 Volts supply is available with the plumber. This machine has a thermostat light on it. Welding of pipes and fittings should be started only when this light goes off. Tell the plumber to keep that in mind. The light goes off only when the welding machine reaches a temperature of 2600C, the right temperature for welding. There is a welding depth mark on the pipes. The pipes should be heated up to this mark only. Care should be taken that when the heated pipe is inserted in the heated fitting, the fitting covers full welding depth of the pipe. More tips will follow next week. Till then, happy building!
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