Repairing or replacing leach field

[MrDrain]

A relative has a 20-year-old house with a field in a remote area. The liquid run-off from their septic tank (which is regularly emptied) is combined with water from their gutters and flows into a 75mm diameter perforated plastic pipe under the field (not near any streams or rivers).

In recent years, the perforated pipe has been unable to handle flow. I've stuck about 10m of drain rods into the pipe without hitting an obstruction, but it's probably much longer than that.

I'm reluctant to get professionals in, partly because they might want to bring the entire system up to modern standards.

Any ideas on DIY approaches for fixing it?

- More drain rods and a camera?

- Pressure washer with a jetting attachment?

- Dig test holes to inspect the pipe at intervals? There are some trees that I'm suspicious of.

- Hire mini digger and put in more perforated pipe to share the load?

[Jules Richardson]

What's the total pipe length? Ours is 4" diameter pipe, around 200' in total (divided between 4 runs of 50' each) - and that doesn't handle any of the guttering, just run-off from the septic tank.

I think you can try flushing it, and it sometimes works. Sometimes it just needs digging up and replacing (if I remember right, ours is only about 18" below ground)

cheers

Jules

[snot]

Does your relative own the field in question?

Neighbour has had horrendous problems here 'cos I the relevant field was built on.

I dare not ask....................

[The Natural Philosopher]

actually problem is that over time soil compacts around perf pipe and even if its laid in shingle. soil percolates into that and clogs it. Dig up whole pipe and relay.

[harry]

not by this site

Aside from other replies, it's a bad idea having rainwater going into a septic tank. It flushes unrotted crap into the leachfield. Also cools the septic tank so slowing the rotting process.

The longer the crap stays in the septic tank the better. The warmer the water the better.

You will probably have to dig up and relay with fresh gravel. It's quicker than you think these days with plastic pipe. Newer septic tanks retain fine sediment better than the old, so prolonging the life of the drains/leachfield.

There is no other long term solution. Jetting may work for a while but the problem will return.

[Chris Hogg]

by this site

+1

If possible, you should separate the rainwater drainage from the sewage/foul water, and dig a separate soakaway for the rainwater. This doesn't have to be sophisticated; ours is a pit, about four or five feet cube lined with staggered concrete blocks (IYSWIM), loose laid on their sides (i.e. no mortar), so there's plenty of opportunity for the rainwater to soak away, the whole covered with a slab of concrete laid on corrugated iron with crude manhole access (a large heavy slate slab), with about 4 inches or so of soil on top to disguise the whole thing. It must be about 60 years old and still perfectly ok, if a bit primitive. It's completely hidden under the lawn, and you can only tell where it is in a dry summer, when a square of grass goes prematurely brown in that particular position.

This will take the pressure off the existing septic tank drainage and you may get away with doing nothing to it at all.

[polygonum]

by this site

He didn't say the rainwater goes into the septic tank, merely that the outflow of the septic tank and the rainwater are combined as they go down the perforated pipe. As I read it, he was quite specific about that.

[MrDrain]

Yes, that's one positive feature of an otherwise slightly cowboy-ish system. The water from the gutters is only combined with the run-off from the septic tank downstream of the septic tank. I think the height drop between the septic tank and the settling-pit where the mixing occurs is about 30cm. On the other hand, when the leach field is really struggling during heavy rain, there's a risk of the water backing up into the septic tank.

[Chris Hogg]

A separate soakaway for the rainwater would still take the load off the leach field and reduce/eliminate the problem there.

[GB]

I don't know anything about this at all, but I wondered what type of soil it is locally? Lots of clay, or lots of sand?

I can well imagine that the pipe itself is fairly clear but the surrounding soil becomes choked with fine particulates, reducing the flow of water that can go through the system.

[Brian Gaff]

Maybe the ground is just saturated and thus the water table is up to the pipe.

Brian

[Man at B&Q]

s not by this site

FFS Harry put your reading glases on.

MBQ