Plastic Plumbing

With a certain amount of skill, and the use of plastic plumbing, you can make a successful job of most new plumbing and drainage installations and repair work around the home. The development of plastic plumbing materials has now made the job much simpler, and the materials themselves have some important advantages over the more traditional metal alternatives.

Plastics are now used for many aspects of plumbing, including cold water systems both above and below ground, waste and soil pipes, drainage systems and complete rainwater systems. Items such as lavatory cisterns, baths, sinks and basins, cold water storage tanks and even one-piece drainage inspection chambers re also available in plastic. Most manufacturers can supply comprehensive literature on their products and it is well worth acquiring a selection for reference.
Lightness and durability are, generally speaktng, the main advantages that plastics have over metals. Even large diameter drain pipes can be h ndled easily by one person. The pipes are, too, usually made in longer lengths than other types, so fewer joints are required and this helps to simplify installation.Plastic pipes have the added advantage that the properties of the plastics used for cold water supply pipes safeguard against the risk of the pipes'bursting if the water inside freezes.

Then is actually less likely to freeze in the first because plastic is a much better insulator an metal but if it does, the elasticity of the, permits the pipe to expand a little without not corrode, and the inside of the pipe is very smooth, so there is little chance of deposits building up inside and obstructing the flow of water. If a plastic water system does fail, it is more likely to be because of a faulty joint rather than a fault in the pipe itself. Another bonus is that plastic pipes are less susceptible to 'water hammer'-so you won't have to worry about strange noises in the night)

The comparative lightness of plastic not only makes installing pipework much easier but it also pays dividends when you are installing a large piece of equipment like a water storage tank. Anyone who has attempted to install a heavy, bulky galvanized-metal storage tank in a loft will know the problems involved in getting it into position. Now you can obtain a special polythene tank that can easily be installed in the loft by one person-and it can also be squeezed through a loft hatch smaller than its own dimensions.

Plastics are not, however, the ideal plumbing material for all requirements, despite their many advantages. Most plastics cannot be subjected to much constant heat, so their use is normally confined to pipework and fittings for cold water services, drainage pipes and for such things as waste and soil pipes where the pipe will not be full of hot water for any length of time. Research is, however, being carried out to find a plastic suitable for hot-water supply systems and central heating systems, and there is every indication that this will be successful. Until specifically hot water pipes become available, however, you must be careful how you use plastic pipes and follow the manufacturer's instructions as to when you can fit them.
Plastic also has a fairly high coefficient of expansion, which means that special care is needed to ensure that the pipes have room enough to expand and contract during temperature fluctuations. Also, plastic pipes, unlike metal ones, are not suitable as earthing points for electrical installations, so another method of earthing must be adopted.

Plastic pipework

Various types of plastics are used for pipework and it is important to know the correct type for the particular job in question-a plastic suitable for one application may not be suitable for another. Before starting any work it is very important to check with your local authority that the material you intend to use is acceptable.
Plastic pipes can be made of polythene, polypropylene, polyvinyl chloride (pvc) and acrylonitrile butadiene styrene (abs) and there are different types within some of the groups.
Polythene (or polyethylene) pipes are available in two forms-low density polythene and high density polythene. The latter is more rigid and can be subjected to marginally higher temperatures, but neither is suitable for carrying hot water. Low density polythene pipes larger f than 2in. (50mm) in diameter must not be used v below ground as their softness would result in the pipe being crushed by the surrounding earth. Small diameter polythene pipe can be'obtained in long coils (up to about 500ft) which considerably reduces the number of joints required in any pipe run.
Pvc (polyvinyl chloride) is used for the majority of soil pipes and drainage pipes as well
as some waste pipes and normal cold-water pipes. Again, two basic types are availablerigid or unplasticized pvc (upvc) and flexible or plasticized pvc. The former is generally used but neither type is really suitable for waste pipes that have to pass very hot water from washing machines and dishwashers. A special high temperature pvc has been developed, however, which is perfectly suited for hot water systems.
Abs (acrylonitrile butadiene styrene) and polypropylene are both plastics with a relatively high softening point and both can be used successfully for hot-water waste systems.

Cutting and bending pipes

All plastic pipes can be cut with a fine toothed saw, preferably a hacksaw. Always take particular care to remove all burrs from the inside and the outside of the pipe with fine glasspaper after cutting. If left they may prevent a good joint being made, and any burrs left on the inside of the pipe will tend to collect deposits carried in the water.
You can bend small diameter pipes by hand but for large diameter pipework it is easier to obtain pre-bent lengths of pipe rather than trying to bend a straight pipe yourself.
The method of bending depends on the type of plastic used. Polythene pipes can be bent either cold or hot. If you are bending low density polythene pipe cold, the radius of the bend must not be smaller than eight times the external diameter of the pipe. Note, however, that clips should be positioned close to the bend to stop the pipe straightening out. If you apply heat to the pipe the bend will be permanent, and you can form a bend with a radius as little as three times the external diameter of the pipe. Use either boiling water or a blowlamp to heat the pipe. If you use a blowlamp, take care that you move the flame continuously over the whole length of the bend-if you don't the pipe will melt.
An internal bending spring must be used to maintain the shape of the pipe while it cools.