Drain project and soakaways designing first footsteps
The first thing that you will need to think about when undertaking any DIY plumbing and drainage are the regulations issued by your Local Authority. You will also need to check their rules for soakaways.
You will have to present detailed plans for the proposed sewage work when you are changing existing drainage system or installing a new drainage system, and also need regular inspections to be undertaken to ensure that the plans are following the local building regulations during progressing each phase of the work. In many situations when you are simply replacing damaged parts or maintaining soakaways, there is no need for the local authority to be informed.
If you hear the term ‘surface water’ in any sewage documents this basically means rain. In older properties this surface water can find its way into the foul water sewage system, but more generally it can also end up in a watercourse, surface water sewer or soakaways. The rainwater pipes in combined drainage systems empty their discharge into the foul water drains through gully traps, this prevent foul air from escaping outside creating unpleasant odours. But modern systems are especially created so that dirty water and surface water remain separate. Foul water should never be connected to surface water drainage system, the soakaways, with any new drainage development you undertake. If you are unsure about the sewage system around your house get advice from the Building Control Department before you start any work.
Before you begin, you will need to plan the underground route of the waste pipes. The main things to consider when planning the route of a waste or soil pipe are to keep the route as straight and short as you can. If the pipe slope to the sewers or the soakaways is excessive, your joint alignment may fail. Using surveyor’s site level you can calculate the fall of a drain over a distance to check the values. If you do not have one of these available, establish a datum point and use a hose filled with water to establish levels and calculate the fall from the datum this way.
When installing your drain trench, you will need to make sure that you do not impinge on or impair the stableness of the building. If you are laying a drainage run parallel to the home, you must ensure that any foundations are not undermined.
Do not dig the ditch too long before laying the pipe when installing a new drainage system. The pipes should be laid quickly and the ditch back filled after the system has been examined thoroughly and tested as required.
You may need to provide some support to the trench depending on the soil in that area and the depth of the ditch. Avoid risks when working in the ditch. If you have any worries, you should support to the trench to reduce any risk of collapsing side walls during the building phase. Make sure that you leave enough room in the trench for you to work but try to keep it as small as possible. The base of the trench should be clean and even and free from protruding stones or bricks etc. If the existing soil is too weak or clayey, you should place and compact a layer of firmer soil at the base of the ditch to prevent later sinking.
You should definitely not use hard materials such as bricks to support the pipe in the ditch. Even if used for just a temporary support this can damage the pipe. The bedding should be properly compacted with hollows made to accommodate the joints in the pipes. For the complete pipe length you have to provide a continuous and uniform support.
It is important that all parts of your sewage system and soakaways are designed so that all parts of the pipework are accessible to a set of drain rods. Which means that a run of drains must be installed straight between two points. As a general rule, any change in direction of the pipework should be provided with an inspection chamber to allow rodding access.
DIY plumbing and sewage is certainly within the limits of most DIY enthusiasts as is typical development of soakaways.