Fittings For Waster Systems

Pipe
Different plastics are available, including ABS. polypropylene and uPVC. Support horizontal pipes about every 500mm. vertical pipes about every 12m. Basin pipes connected to a single-stack system are restricted to a maximum length of 3m unless special precautions are taken (special automatic resealing traps or designing the system with separate ventilation pipes, for instance).

Flexible waste pipe is also available particularly useful under sinks and basins.

Sockets
For joining lengths of plain ended pipe together. Available for all methods of joining. Some sockets have a plain end to take another connector instead of a pipe.

Bends
For taking runs of 'horizontal' pipe around corners. 90 degree and 135-degree angle bends are most widely available. Waste pipes should slope (but often only slightly) towards the outlet - to connect these to vertical pipes, use 91-degree or 92-degree bends. Some bends have a plain end and adjustable - swivelling - bends are also available.

Tees
Common angles are 90, 91, 92 and 135 degrees. Tees are usually swept in the direction of the flow (the tees should be fitted so that the direction of the bend from the branch into the main pipe is the same as the direction of the flow of water). Avoid using tees for joining two waste pipes that then run to a single-stack system wastes should be connected individually to the stack.

Connectors
Various types are available for connecting pipe to different fittings. Reducers can be used for joining 32mm or 40mm pipe to 40mm or 50mm pipe. Copper compression can be used to connect plastic pipe to existing copper wastes. BSP screwed thread can be used to connect pipe to a waste outlet in sinks and so on. Jointing paste must not be used on screw threads, but PTFE tape can be used if necessary.

WC connectors
The easiest joint to make to a WC is with a plain-ended connector. This should be dry-jointed to the WC outlet, using a rubber gasket. Various patterns of connector are available with different angles and lengths of plain-ended spigot (depending on the position of the WC pan and the soil pipe to be connected). For particularly awkward joints, a Multi-kwik connector can be used - again, various patterns are avail¬able, including one that will cope with slight displacements between the pan outlet and the soil pipe.

Traps
P traps have a horizontal outlet; S-traps have a vertical outlet. Trap inlets usually have BSP threads for connecting directly to waste outlets. Shallow-seal traps can be used on wastes discharging into gullies or hopper heads; on single stack systems deep seal (75mm) traps should be used. Deep-seal traps take up more room, and to install one beneath a bath you may need to cut away the floorboards. Bottle traps are neater than tubular ones and may be easier to use in tight spaces instead of a deep-seal trap -they should not be used on waste disposers. Bath traps often come complete with over¬flow system attached. Washing machine traps have an inlet at the side for taking a washing machine outlet hose - the trap replaces the sink trap. In some situations, automatic resealing traps may be necessary - for example, for extra-long basin wastes connected to single-stack systems.

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Plastic Waste Pipe Systems

Plastic has replaced traditional materials like lead and copper in the manufacture of waste pipes. Waste pipes are the part of the plumbing system that carry waste (foul) waster from appliances such as washbasins, baths and showers, urinals, kitchen sinks, washing machines and dishwashers to the soil pipe system. The soil pipe system then in turn connects to the underground drainage system.

There are three types of plastic used in the manufacture of waste pipes. These are PVC (Polyvinyl Chloride), ABS (Acrylonitrile Butadiene Styrene) and Polypropylene. All three systems are commonly used in domestic waste systems, whilst PVC is the most commonly used material in commercial installations.

Both PVC and ABS waste systems are known as "solvent weld" systems. This means that joints are made by using a chemical substance (solvent cement) that effectively breaks down the plastic pipe and the joint or fitting and welds or fuses the two parts into one. This makes the joint completely permanent, and unable to leak. Polypropylene waste systems are joined using push fit fittings that incorporate a rubber seal. The simplicity of this system makes it a favourite for DIY fans, as provided the pipe is cut square and clean and the pipe is correctly inserted, the system is easy to assemble. It can also be taken apart and re-assembled if some adjustment in the waste pipe installation is required.

All three systems are designed to cope with the rigours of the domestic waste system. PVC has the best resistance to extremes of temperature, acids and other chemicals and hence this is the material that is usually specified for more commercial installations such as hospitals, police stations and launderettes. Installations such as science labs or photographic laboratories often need even stronger grades of specialist plastics due to the waste chemicals involved.

Waste pipes and fittings come in three sizes, 32mm, 40mm and 50mm. These sizes correspond to the old common imperial pipe sizes of inch and a quarter, inch and a half and two inch. Many plumbers still use this terminology when ordering their materials, so it is important that staff have an understanding of both imperial and metric sizes. Pipe manufacture is not standardised, and most manufacturers produce slightly different size variations - 32mm could actually mean anything from 32mm to 36mm in practice. This means that not all systems are interchangeable, so if you are repairing or extending an existing installation you should ideally take a piece of pipe or a fitting to the retailer to check that the new fittings will actually fit. If they don't fit, don't worry - most manufacturers make a multi-fit compression style fitting that enables to you to join different types of material, including other plastics, lead and copper.

As a rule of thumb, 32mm pipes and fittings are used in conjunction with washbasins (including vanity basins) and some urinals. 40mm is used when connecting to baths, showers, kitchen sinks and other kitchen appliances such as washing machines and dishwashers. Some urinals also have 40mm outlets. 50mm pipes are generally used when a number of appliances use the same waste pipe to join to the soil system, for example in a public convenience where a number of urinals are connected in series to a common pipe.

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