Foul drains carry used water and solid waste from toilets, sinks, baths, showers and other sanitary fittings as well as washing machines and dishwashers.
Above-ground pipework is referred to as sanitary pipework; the underground pipework is referred to as foul drains and foul sewers. (Generally speaking, a drain serves a single property while a sewer serves several properties.)
Plastic drain-pipes are now used, and are much less susceptible to cracking and breakage than the earthenware pipes which had been used previously. Earthenware pipes can have a very long life, but subsoil movement or tree roots can lead to fractures or pipe joints failing. Any such breakage or leaks in foul drains will have serious consequences when sewage leaks into the surrounding area.
Drains are also liable to blockages – this is particularly liable to occur when solid matter collects at bends or joints in the pipe run – which will require removing. If blockages occur frequently this may be due to a design fault in the system, requiring a new installation.
A full building survey will include lifting an inspection cover if possible so as to see if waste water is running through the drainage system satisfactorily. If a problem is suspected then it may be necessary to employ a contractor to insert a CCTV probe through the pipe to locate the broken pipe or blockage.
Building over an existing drain or sewer can damage pipes, as well as making it more difficult, time consuming and expensive to clear blockages and repair or replace faulty drains. Homeowners should therefore check the position of foul drains before starting any extension or other work which might interfere with them. Determining the location of foul drains usually requires a survey, as maps are rarely available, but it is always best to contact the local authority and water company for advice.
Until recently homeowners could be liable to contribute to repair costs for lengthy runs of shared or combined drains serving several properties. However since 1 July 2011 all sewers and lateral drains are publicly maintained if they connect to the public sewerage system and serve more than one property. Homeowners do remain responsible for any foul drains solely serving their own property.