The Natural Philosopher wrote in message

Well I haven't touched my klargester in 4 years and its running fine.

Its sized for 6-8 people because that's the house size, but only two use
it mainly...

I guess it will need emptying in a few years. Its supposed to be the
sort of 80 quid a year call out and pump thing, but I suspect I may
simply get in with a spade and wheelbarrow and dig out most of it and
stick it on the compost heap one day...

Thanks for the info TNP!