Most of my work is replacing septic tanks with sewage treatment plants. Soakaways always fail eventually, regardless of the rainfall, so discharging directly into a ditch is a better and cheaper option than replacing a soakaway.
Most people don't have a big enough garden for a soakaway these days anyway. After the soakaway tests, the average soakaway that I put in is over 100M2 and all of it must be 15 metres from a building. Not many people can do it as it can't go under a drive or parking area either.
I put a sewage plant in just before Christmas for a bloke who had replaced his soakaway 5 times in 22 years. He reckoned he had spent over £15,000 in total for soakaways that always failed.
