Drainage

There are basically two kinds of drainage systems: surface drainage and sub-surface drainage.

If your property is built before 1937, domestic drains are usually the responsibility of the individual householder; at least until the drain reaches the point at which it interconnects with the drains running from other properties whereupon it becomes the responsibility of the local authority.

With properties built after 1937, a record is generally kept by the local water authority.

Modern approaches

Increasingly, industry experts are starting to consider sustainable drainage systems (SUDS) which involves dealing with surface water at source (source control) by directing it into the ground where it belongs.

The technology involved in this approach can include the following:

• Permeable paving – most permeable paving includes the use of block paving although new technologies can allow other materials such as asphalt and resinous surfacing to be used.

• Infiltration and attenuation systems – involves the installation of a soakaway system.

• Filter drains – modern filter drainage systems incorporate geotextile filters which are designed to prevent fine grains of soil from passing into the drain and causing a blockage.

• Swales – merely ditches cut into the earth and are commonly found running alongside roads for example.

Modern filter drainage systems

Modern filter drainage systems involve the laying down of geotextile filters which act to prevent fine grains of soil from passing into the drain and blocking it. These filters are made from synthetic textile fabrics which are specially made for the civil and environmental engineering sectors.

They are generally laid along a trench and overlaid with course granular material such as gravel or stone. The fabric is then passed over the granular material and the trench filled in with earth. The advantage with such filters is that they tend to be fairly cheap.

Linear drainage involves the laying of some kind of enclosed channel with a U-shaped cross section and some kind of grating installed over the top. These are available in a multitude of forms and many of them are made from polymer concrete units for driveways or stainless steel units for commercial premises.

Other materials can include plastic, wet-press concrete, galvanised steel and HDPE (High Density Polyethylene). Gratings are available in various classes, from cheap Class A gratings made from galvanised steel and sold in large DIY stores right through to milled aluminium.

Piped drains are made from a variety of pipe units including vitrified clay, uPVC, concrete, iron and asbestos. They come in two forms – plain end and socketed. Plain end pipes consist of pipe units that are connected by a coupling mechanism whereas socketed have ‘male’ and ‘female’ ends that insert into one another. The latter type must be laid with the ‘female’ end pointing upstream. Vitrified clayware tends to be much stronger than plastic.

Blocked drains – causes and signs to look out for

Signs of a blocked drain include foul stenches, outside gullies and manholes overflowing or a toilet not flushing waste away properly. Other signs include smelly sinks or a strange gurgling sound when you flush the toilet or empty water from the bath or sink.

A blocked drain can be caused by:

• Systems being abused by flushing disposable nappies, sanitary products and similar materials that can cause a blockage. Waste should be disposed of properly and these types of items should never ever be flushed down a toilet.

• The disposal of paints and solvents and cooking fats and oils can cause pipe work to block.

• Tree roots in broken drains.

• Drains generally being in a poor physical condition.