Septic Tanks Woes

[Plumpplumber]

My sister recently bought a house with a septic tank. There was leakage out behind the tank and the tank itself was well overdue for a pump out so we got it emptied and excavated behind the outlet only to find a fairly crude soakaway which had failed leaving a foul smelling mess. We extended the outlet pipe to another area of the garden, built a new soakaway and a soakaway overflow for good measure draining to a stream.

Everything appeared to be working fine for a couple of months until we started to get bad odours from the soakaway overflow, with water obviously coming right through the new soakaway. The house is built on clay soil and when the new soakaway was excavated the digger driver did his best to dig down past the clay layer as far as possible but it's looking as if this has been unsuccessful and the soakaway is already flooded.

It's looking as if we need to find some other means of absorbing the effluent (possibly taking all the grey water out of the equation by filtration or similar so that the soakaway has less work to do) but what puzzles me is why there is so much smell coming from effluent that has been 'treated' in the septic tank and I'm wondering if the tank is actually 'working' from a biological point of view. My understanding has always been that the treated effluent from a septic tank should be relatively odour free.

The tank is about 40 years old of concrete construction and unusually big for the size of the property. It has no internal baffle and the inlet and outlet 'tees' are in place. There are only two people in the house and they are scrupulous about not using harmful chemicals, bleach etc.

Could it be that the tank is actually too big and the ratio of water to solids is too high thus preventing the biological action from working efficiently?

Anyone got any tips on

a) How to get a working soakaway in clay soil.

b) How to eliminate smell from the tank outlet.

 

[Dotty]

Her name's not Meg by any chance?

 

[Plumpplumber]

Her name's not Meg by any chance?

Nope. Am I missing something?:wink5:

 

[Dotty]

Nope. Am I missing something?:wink5:

We had an American visitor last year with septic woes.

Ended up with her showing us her selfies possibly with the back garden behind her. None of us could see past the low cut tops....

 

[Plumpplumber]

LOL! Nah, this side of the pond and not even a durgo showing........ :blush2:

 

[Dotty]

LOL! Nah, this side of the pond and not even a durgo showing........ :blush2:

Awwwwww....

 

[Ermintrude]

Reed bed mate. U sound like its aerobically digesting .

BE VERY CAREFUL! That tank will kill you and anyone who gets in it. DO NOT enter and please get some assistance. U need some confined spaces kit and training before u go near it.

I would look at the soundness of tank. Possibly clean it and get some bacteria. Is she using a lot of bleach and biological washing liquid by any chance?

 

[riksony]

I live across the pond in Ireland where most people have septic tanks. A good working tank should not need emptying. Ermintrude has a good point about adding bacteria or you could try a good product called cessclean and flush this down the pan as instructed.

 

[Plumpplumber]

I live across the pond in Ireland where most people have septic tanks. A good working tank should not need emptying. Ermintrude has a good point about adding bacteria or you could try a good product called cessclean and flush this down the pan as instructed.

Interesting you say this! We're in Scotland and my own septic tank (as opposed to sister's one!) is around 60 years old. We have lived in the house 58 years and I cannot recall it EVER having been pumped in all that time. It works perfectly - no smell whatsoever. We don't ever consciously think about avoiding any particular cleaning products and all the waste water goes down it (including grey water and guttering!) I'm well aware about the dire warnings online about blocking soakaways etc if not pumped but I don't even know if there is a soakaway. An old lady who witnessed the tank being installed in the early sixties told my parents the tank drained down a pipe through a field to the sea. Maybe she was right!

 

[Plumpplumber]

Ermitrude mentions 'aerobic' digestion (as opposed to anaerobic) I'm assuming it shouldn't be doing this. It's not a modern tank with pumped air or anything like that. The tank is very big though and I suspect the ratio of water to solids is too high for anaerobic digestion to get going. We threw in a dead pheasant after the tank was cleaned out to restart the process but I see opinions vary about the sense of this (different kind of bacteria?)

Maybe a commercial additive is the answer to kick start it?

A reed bed might be worth thinking about too but there's not much available space in the garden.

 

[Ermintrude]

A dead animal. Brilliant idea.

Perhaps u would be better Iusing jays to clean it out and then starring again.

Anaerobic relies on a good 12" of water over the plop.

 

[Plumpplumber]

The tank's full again now (mostly water) so doo doos are well submerged. No crust formed yet. Would the sheer size of the tank and amount of water affect the process if input of solids is relatively small?

 

[joni os]

In 1970's when block and render was permitted, many tanks were constructed to large dimensions. Some continue to function well after 40 years, without ever being emptied.
However, even in those happy days, direct discharge to ditch or water course was prohibited.
This aspect of your scheme should be corrected without delay.
Construct second chamber, next to first, with inlet and outlets tee'd and inverts level throughout. Keep your weeper drains within 500mm of surface.

 

[oz-plumber]

You may just have to dig in new soak away drains.
Depending on the drains installed and the soil ( clay ) you might find the soak aways have had their day.

Recently had to do this at a residence with clay soil. The soak away drains were 25 years old.
There was no other solution.

 

[Plumpplumber]

In 1970's when block and render was permitted, many tanks were constructed to large dimensions. Some continue to function well after 40 years, without ever being emptied.
However, even in those happy days, direct discharge to ditch or water course was prohibited.
This aspect of your scheme should be corrected without delay.
Construct second chamber, next to first, with inlet and outlets tee'd and inverts level throughout. Keep your weeper drains within 500mm of surface.

Would the second chamber help combat the smell? We've already tried digging a new soakaway but it's just really a very deep pit with stones and seems to have failed within 3 months. There isn't much room for a more extensive layout of weeper drains short of digging up the whole garden. Would this be any more successful in clay than a single pit?