Septic tank soakaway

[thelostcause]

Hi all,

My septic tank soak away has come to the end of its useful life according to a drainage survey and requires replacement. I have been searching around on the internet for advice on how best to construct a new one but have come up against a lot of conflicting information. My property and the septic tank along with the soak away were constructed in 1967 so does not appear to be covered by most of the regs I can find which relate to new septic tank soak aways. The present soak away is a pit that is filled with rubble,we already have environmental agency approval for discharge to ground for this, but has become silted up over the years and subsequently blocked. My question is what can I use to replace this soak away, can I use the plastic crates with membrane and stone, some companies say this is fine as it is over 15 years old but others state that it must be a drainage field constructed from rigid slotted pipe in a loop with stone and a membrane. Any help on clearing this up would be greatly appreciated.

Thanks in advance Paul.

 

[Burnerman]

The biggest issue Paul is who owns the land that your outfalls encroach on......would they give you permission for excavation plant to access?
Outfalls don't need to end in any sort of underground pit - slotted plastic drainage pipes are absolutely fine, so long as there are enough of them.....the ends of my pipes terminate in a mound of stone.
With mine I was able to hire a digger with a trenching shovel and once the trenches had been dug I lined them with ballast, installed the outfall pipe and then covered them with ballast again.....eventually covered by the original topsoil. I was able to lay the pipes in a herringbone pattern to give more drainage than was really necessary, courtesy of the land owner who couldn't have been more helpful.
John

 

[thelostcause]

Thanks John, I have permission from the land owner to carry out repairs to the soak away. The reason for me asking is we have received a quote for the better part of £4,000 plus VAT for a new herring bone system!!! I found the crates on the internet and could by them for around £600 hire a machine for £100 and do the job myself, providing the crates are acceptable as a septic tank soak away. This is what I would have done but the septic tank is shared with my neighbour and he is concerned that it is done correctly.

 

[Burnerman]

With care - i.e with what goes down the loo - a new soak away can last many years......this depends on the porosity of the land, obviously enough! The length of the soak away depends on the same.
Original soak aways consisted of porous clay pipes, from which the liquid would leech through.....a small gap between the pipes, covered with stone, helped things along. Today's plastic pipes are so much better, but of course they too can silt up.
A large pit with various objects to keep the underground cave open will work fine, so long as it isn't overloaded.
Does the septic tank back up.....that is, the outlet chamber remains full? Always the sign of alarm.
I'd assume your neighbour would share the bill?
John

 

[thelostcause]

The tank has never backed up and is always emptied annually, we just get a large wet soggy patch over the soak away where it has become silted up. As regards the porosity of the land we have very good drainage apparently after the land was tested, the soil is sandy and is mixed with rejects. It looks as though the pipework to the existing soak away was replaced with 4" plastic pipe some years ago, before we moved into the property.

My neighbour would share the bill but as a pensioner he has limited funds and has asked me to look at other solutions. This is when I came across the plastic crates and thought they would be an ideal much cheaper solution to our problem, as long as they are suitable for septic tank soak away.

 

[stuart45]

The idea of the soakaway loop is to give a second treatment to the waste, which require the pipes to be closer to the ground in aerated soil. A deep pit will allow water to soak into the ground without treating it properly so technically isn't correct. Saying that I know mine was done like that years ago but it wouldn't get past the BCO now.

 

[Burnerman]

Yep, that's perfectly fine.....obviously the original stone soak away has become silted up so it looks like it's time to either excavate the whole thing, or divert your outfall pipes in the direction of a new one.
There's nothing wrong with plastic crates filled with rubble - this method is used often enough. The bigger, the better!
At least, your neighbour won't be producing much waste anyway - unlike a family of 5, for example!
Obviously, the wet patch means your existing system isn't draining to earth so that's for concern.....but nothing to really panic about, so long as the land owner isn't concerned.
John

 

[thelostcause]

The idea of the soakaway loop is to give a second treatment to the waste, which require the pipes to be closer to the ground in aerated soil. A deep pit will allow water to soak into the ground without treating it properly so technically isn't correct. Saying that I know mine was done like that years ago but it wouldn't get past the BCO now.

I didn't think that I would need BCO approval to replace an existing soak away, does it require Building regs ??

 

[stuart45]

If you're going to dig a big pit and use soakaway crates then don't get Building Control involved. If you ring them up and ask them they will probably tell you that you do need regs.

 

[Burnerman]

+1 for that! Exactly the advice I got before I got stuck in.
Are there any water courses nearby?
John

 

[thelostcause]

there is a river around 50 meters away from the soak away site, according to the environment agency web site this is okay?? There are no wells or drinking water collection points locally.

 

[Burnerman]

No problems with that one.
John

 

[chappers]

As others have suggested, I would just consider sorting the soakaway you already have, after all it has served you well enough for 50 years. Excavate the existing soakaway and do as you suggest, even enlarge it slightly if you feel more comfortable with that, my guess is that back in 1967 it was just a hole filled with all sorts of rubble and probably not even very well protected from silting from the surrounding soil. You would now have the opportunity to wrap your new soakaway in membrane and protect it that way. You might also want to look into adding a second smaller settlement chamber into the system which would again help to further enhance the life of the soakaway.

 

[thelostcause]

You might also want to look into adding a second smaller settlement chamber into the system which would again help to further enhance the life of the soakaway.

My septic tank already has a settling chamber built into it so that is already there.

So it looks as though the black crates will do the job then. Thank you all for your replies.

 

[theprinceofdarkness]

I know of a soak a way that was built new in 1973 with the outlet pipe that ran down hill. Ever since then there has been a muddy patch in the field. I do not know what the "design" was. Its still in current use. This has made me very cynical about herring bone fields as the water will always run to the lowest end, so the rest of the field is wasted until the lowest bit blocks up.
Frank