On Fri, 3 Aug 2018 19:13:23 +0100, NY wrote:

I've never dared open the inspection cover of the septic tank. On a
scale of 1-10, how bad is the pong, typically?

It's not really bad, "fruity" has been used, "sweet" "warm".

What is the consistency of the contents? Is it mainly liquid?

Depends on how long it's been since it was last pumped out, how big
it is and how many people are using it.

Recently had our large tank pumped out after about ten years and less
people than it's size can cater for. It was pretty full of "solids",
think 5 years would be about right. The bulk of the (two compartment)
tank should be water with a soft crust on top and solids in the
bottom.

A septic tank is anerobic and the outflow is pretty foul and has to
go into a buried soakaway. If you have a "klargester", ie a
mechanically stired and aerated system the out flow should be clean
enough to discharge into a water course.

--
Cheers
Dave.