Strangely enough this subject came up recently when a relative of mine was having their septic tank pumped out. The fumes generated by the normal decomposition of waste in septic tanks and cesspools are a very unpleasant mix of toxic gasses, so much so that people are warned never to breathe in...
I just find it hard to comprehend how anyone could throw the body of the woman he claimed to love, and her beloved pet, into somewhere like that. It doesn't bear thinking about.
Yes, which is odd as it doesn't really look like it was originally designed for that, but it may have subsequently been adapted for that purpose I suppose.
...actually from looking at the cross-section drawing I don't think it's a septic tank or cesspool at all, but rather an old rainwater storage cistern like this for example:
http://www.milesgolding.com/cistern.html
It may well have been there long before the garage was built on top of it.
It's not unusual with older properties for there to be no plans of the drains, particularly where there is a septic tank system not connected to mains drainage. There were few regs in those days, and individual builders all tended to do their own thing with regard to septic tanks. I've owned a...