"Jimk" wrote in message
news
Having recently bought a house with a septic tank, I looked into this. As
far as I can tell, existing septic tanks can continue being used until
further notice, but a new installation (and maybe a replacement for a
failed
septic tank) has to be a mini sewage works - at great cost, and making a
constant loud hum from the motor that stirs the contents.

Since our septic tank is under the patio where we sit in the sun,

Cesspit then? Not a septic tank then ?
Unless it has multiple chambers & an outflow to "somewhere"?

Yes, a septic tank. I presume it has multiple chambers. It discharges to a
soakaway under the lawn. That's what the vendors said, and the grass in that
bit of the lawn does grow a little bit quicker, though that might also be
cause the ground is lower there so closer to the level of the surface water
in the ground.

How often does a septic tank need to be emptied of solids which don't fully
rot down, even though the majority of the liquid is discharged (after
processing) into a soakaway?