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?
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.
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.
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.
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.
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.
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