High performance pipes

Jagvir Goyal

Treatments and cures are available to repair and stop any leakage noticed in the walls or ceilings of rooms, but it is always better if such problems are avoided altogether by taking certain preventive steps during the construction of the house and then taking some post-construction care. Let's consider the pipes provided in a house and in the roof slab and the steps to be taken to keep them leak proof:

Water supply pipes

Three types of water supply pipes are generally used these days. These are GI pipes, PVC pipes and Composite material pipes. PVC pipes are either uPVC pipes (unplasticised pipes) or PPR pipes (Poly Propylene Random pipes). Each type of pipes has its plus and minus points. Whatever pipe material the user chooses for his house, the most important point is to ensure that these these pipes don't have any weep holes or hairline cracks.

During the laying of water supply lines, the joints should be made fully leak proof and the pipe network should be pressure tested to check if there is any leakage in pipes or joints under water pressure. No water supply pipe should be laid under the floors. These should be carried in the walls only by cutting chase in them. There should be very less joints in the water supply network. Sometimes, instead of chase cutting, ducts are provided in the walls and the pipes are carried in these ducts. In such a case, a leaking pipe wouldn't require dismantling of any plaster and brickwork. However, such procedure is adopted only in multi-storeyed buildings or hotels. In case of GI pipes, the joints should be prepared by using best quality cotton yarn thread smeared with white lead over the pipe threads. Quantity of yarn should be kept minimum. For PVC pipes, cement solvent or heat welding or rubber gaskets are used for jointing. In case of composite pipes, the pipes themselves can be bent to any angle and there is no need of preparing any joints.

The pressure testing of water supply network should be done before filling the chases in masonry walls and finishing them with plaster. The pressure gauge should have zero error and the pipe network should be filled with water slowly to allow expulsion of air from the pipes and to avoid the water hammer phenomenon. The water pressure should be maintained in the pipes at least for one hour. Any pipe or joint having even the slightest leakage should be replaced immediately.

Sanitary pipes

In case of sanitary pipes, the choice rests between Cast Iron (CI) pipes and Poly Vinyl Chloride (PVC), SWR pipes. Here the tilt is in favor of SWR pipes. These can be used for soil, water and rainwater disposal. Cast iron pipes are prone to cracks and pin holes and their jointing is often done in an unsatisfactory manner. Lead is to be poured in the CI pipe joints and the process is called lead caulking. The plumbers generally try to save lead and its quality is not maintained. It is difficult to handle CI pipes due to their heavy weight.

SWR pipes are lightweight and easy to handle. When used as sanitary pipes, there are no issues of running hot water through the pipes nor there is any odor problem. Sanitary pipe specials need to be of same material as that of pipes. CI Specials are used for CI pipe jointing and PVC SWR Specials are used for SWR pipes. While lead jointing is done in CI pipes, for PVC pipes, the joints are prepared either by using rubber seal rings or solvent cement. Solvent cement joints should be preferred to make the joints leak-proof. Care should be taken during laying of sanitary pipes that the slope of horizontal pipes is not less than 1 in 50 and not steeper than 1 in 10. Correct slope will help in proper disposal of waste water. By using this tip one can avoid blockage of pipes, further avoiding leakage in joints.

Roof slab

Roof slab leakage has a negative effect on the health of inhabitants of a house. It gives rise to a sinking feeling besides causing damage to the house. In order to avoid expansion cracks in the roof slab, bearing plaster of ½ inch thickness in 1:4 cement mortar should be provided on top of brick walls before resting the roof slab on the walls. Bearing plaster should be coated with two coats of bitumen after the curing and drying of bearing plaster. A gap of 10 mm should be left between the edge of slab and the end course of bricks to take care of expansion of slab during summers. The gap should be filled with sand or a compressible material.

The RCC slab surface should be provided with two coats of 85/25 grade hot bitumen and covered with sand before laying the topping material on it. These days, acrylic polymer cementitious coating is applied on the roof slab. It is breathable and flexible water proofing compound coating and is better than bitumen or epoxy coatings. It is prepared by mixing liquid acrylic polymer and cementitious powder material.

Proper slope should be provided to the slab and roof topping to drain out the rainwater. When there are a number of rainwater pipes, the roof area should be divided into pockets and slope of each pocket should be kept towards the nearest rainwater pipe. All rainwater pipes should be fixed with iron gratings at their top. If you are able to keep the rainwater pipes clear and allow no rainwater to accumulate on the roof then you have almost clinched the issue. All joints of tiles or other material provided on the terrace should be well filled and sealed against seepage of rainwater.

Parapet joints

All along the junction of the parapet and the slab, a concrete triangle (gola) of 2 to 3 inch radius with its inclined side convex towards the corner should be provided before plastering the inner face of parapets so that there is no vertical joint between the plaster and the gola to allow the water to travel. It is important to cover this joint of slab and parapet to avoid entry of rain water from here.

Rainwater pipes

Rainwater pipes too can be in CI or PVC. PVC pipes are preferred these days over CI pipes. While the joints of CI rainwater pipes are filled with 1:2 cement mortar and spun yarn soaked in blown bitumen of 85/25 grade, the PVC rainwater pipes are jointed in a fashion similar to PVC sanitary pipes. In case of rain water pipes, the most important factor to avoid leakages is to keep the passage for water free of any obstructions. A rainwater pipe continues to serve its purpose even if it has hair cracks or weep holes in it provided it is not blocked by dirt. Rainwater flows vertically under pressure and hardly escapes through a weep hole. It is important to cover the mouth of rainwater pipes with iron or steel gratings to avoid entry of any debris in them.

These preventive steps will certainly help in making a house leak proof.

— This column is published fortnightly