On Tue, 28 Jul 2020 19:14:42 +0100, The Natural Philosopher wrote:

Mine was built in the 1930s and the outlet goes to a 3 foot
diameter
soakaway

Then it isnt a septcic tank is it?

They don't have outflows

Yes they do, it's cess pits that don't have an out flow.

--
Cheers
Dave.