Soak-Aways

The soak away is possibly the most important element of any septic system. How well the soak away works is dependant on the soil structure and the structure of the outlet pipe. Traditionally it didn't matter much what you did with the soak away from a septic system so long as it worked, but now there are a raft of regulations enshrined in law to govern how a septic system to allowed to drain and strict penalties for anyone who ignores them. Since 2006 you need to have a new septic system that discharges into the environment registered with the Environment Agency.

One of the conditions for a septic tank system is that you can not reasonably connect your home to a main sewer, in fact if you are planning a new home outside of the 'foul sewer catchment area' then you will be required to contact your local water board to enquire about alternative arrangements (for example setting up a pump to connect to the main sewer). You can get permission for a separate septic system regardless of presence of a main sewer, providing that the system can be demonstrated to be of special merit, and can be proved to be more sustainable than using the foul sewer.

Soak-aways for septic tanks must be of sufficient size to handle the run off from the tank. A typical example would be a leechfield, with a hundred metres or so of well-laid, perforated drain pipe laid out in a zig zag pattern under the surface of a field. If the soil is right, the you can just have a straight length of unperforated pipe that drains into the soil from the end.

The problem with many soak-away designs is that often fail with use, simply due to grease, fat and fibres from the waste clogging the subsoil, or it can become totally water logged if the system doesn't drain properly. In existing and especially older septic systems, if these problems arise then it is usually necessary to perform a full survey of the system to determine the extent and likely cause of any problems. Excavating the entire system is something we would try to avoid, but in the event of a failure within the system, this may be the only solution.

Getting the soak away right can often be the most difficult, especially if the land surrounding your home isn't level. The larger you can spread release of water from the soak away the better. Best would be to use a network of pipes laid level with a series of perforations along the side, and backfilled around the pipe with a granular material allowing rapid drainage from the pipe's immediate area. This allows the pipe to remain half full at all times.

This disperses waste water evenly throughout the entire length of the system, making a longer lasting septic drainage system with little chance of the system failing. Unfortunately, this design of soak away requires very careful design and even more careful construction. But it is preferable to all of the water being released in the first few metres of a hundred metre long system, specially as this is likely to lead to serious problems not too far down the line.