mousetarget

Thanks for the replies. If indeed my drainage field cannot cope with the amount of water passing through the system, because of rainwater going in, what could be a possible solution and how expensive would it be? Would it be just a case of capturing the water coming off the house roof in water butts so it doesn't enter the soakaway system which leads to the septic tank?, a bit of a pain having to empty them all the time though?

Does anyone recognise this design of Septic Tank system? - I've recently moved to a new home and can't find anywhere with a design like this. The waste pipe runs from the house to the bottom of a very deep, 20ft - 30ft concrete shaft, the water and waste then rises to the top (about half way up is a macerator which can be turned on) and there is a plastic pipe at the top which then takes the excess into the septic tank. I've been told that the builder who put it in also connected it in such a way to allow rainwater to access the chamber which I believe is not recommended. The septic tank is then connected to a drainage field in the garden. I've always understood waste pipes connect to the top of a septic tank, and then the solids can drop to the bottom, the waste pipe from the house connects to the bottom on this shaft which confuses me. See attached rough sketch, has anyone seen anything like this before? The system works fine but just want to understand it more?