Plumbing Installation

If you are altering your existing drainage, or installing a new drainage system you must always inform the local Building Control Department at your local council offices. Waste from these sources must always go to your foul water drain system.

Surface water is basically rainwater. This can discharged into a soakaway, watercourse, surface water sewer or, particularly in older properties, into the foul water drainage system. In a combined system, the rainwater pipes are discharged into the foul water drains via gully traps which stop foul air escaping from the drains.

However, modern systems are designed to keep the foul water and the surface water apart. It is extremely important to ensure that you do not connect foul water to a surface water drainage system. If you are unsure about the drainage system around your house get advice from the Building Control Department before you start any work.

You must avoid making your pipe runs too steep. A soil pipe is normally laid to a fall of 1:40. You can calculate the fall of a drain over a distance using a surveyor's site level. If you are laying a drain run parallel to the building, you must ensure that any foundations are not undermined.

Do not dig the trench too long before laying the pipe when installing a new drainage system. If in doubt - add support to the trench to prevent it from collapsing. Keep the trench as narrow as possible, but allow room to work in the trench - say the width of the pipe plus 150mm (6") on each side. Never use bricks and/or other hard materials to support the pipe in the trench. Once the laid pipes have been inspected, granular material should be evenly backfilled and compacted to a depth of at least 100mm above the pipe. Above the granular backfill material, the original dug material can be used to completely backfill the trench. You will need to protect any part of the drain system that is less than 600mm below a garden. A 50mm layer of lean concrete laid 100mm above the pipe will be adequate to do this. Where a junction between two drains does not have a manhole, access should be sited on the branch drain within 12 metres of the junction.