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How to replace a damaged rainwater drain set in concrete?

Postby Exeterphi1 » Sat Mar 20, 2021 11:40 am

Recently moved into a 1950's bungalow to discover a rainwater drain is badly blocked. (Appears to have been blocked for years and years).

I rodded the drain from the manhole on the driveway (10m away) and removed a bucket load of roots, but the bend towards the gully is too sharp to get the rods around. I reached down into the gully to remove all of the impacted soil and roots within reach - it isn't possible to rod from here.

I have tried a high pressure drain hose in an attempt to blast things clear, but to no avail.

Digging down with a view to replacing the damaged section of drain only to find concrete covering the drain pipes. The gully is approx 35cm deep so expect the drainpipes to be a little shallower after the trap

Is this concrete part of a raft foundation and if so, should I carefully break up the concrete to get at the old pipes and replace with plastic?

Or should I investigate a difference method of replacing the damage drainage?

Many thanks


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Simply Build It

Postby stoneyboy » Sun Mar 21, 2021 10:36 pm

Hi exeterphi1
It would be unusual for the rainwater system to be any more than a pipe run directly out from the gulley which may or may not end at a soak away.
Is the manhole you rodded from part of the foul system? This is more likely considering the age of your property.
Try digging around the gulley and see if a pipe leaves it at 45 degrees to your house wall. The concrete is probably your foundations and it’s unlikely that a pipe has been buried in it.
Regards S
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Postby Exeterphi1 » Mon Mar 22, 2021 11:31 am

Hey Stoneboy,

I did think it unusual. However turns out the local builder who constructed these house, took a belt and braces approach.

I first checked around the house and found no other concrete (it was suggested the property might be on a raft foundation).

The pipe runs from the gully, bends around the front of the house and down to an manhole / inspection chamber under the blockwork driveway. I beleive it was encased in concrete to protect the pipes as they at a depth of approx. 30cm, rather than 60+cm where pea shingle and earth is used.

With an SDS drill, I carefully cracked into the concrete exposing the old salt glaze pipe. The large bush (that I removed) that someone planted years ago had borrowed through the concrete and opened up a large crack in the pipe. I pulled out two buckets of roots and mud, to eventually cleared the whole pipe and gully. This was back breaking enough, so opted to replace just the damaged corner with plastic pipe. Everything is now running smoothly with water flowing into the inspection chamber and out to the storm drain in the road.

On to the next job…

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