Problem with sewer pipe through foundations

[garyo]

Hi guys,

I've just finished digging out my foundation trenches. I've found a soil/sewer pipe that I knew was there but didn't expect to be quite so awkward.

It runs in a straight line from the soil stack inside the corner of the house, to a manhole 4 metres behind. It's encased in concrete which I an trim down on the edges, but it's still awkwardly placed.

In the diagram below, the red lines indicate where I need to build a cavity wall. The pink line indicates DPC/floor level. What are my options for lintelling over this? I really don't want to have to lay a new sewer run.

I was considering excavating two pads either side (shown in green), then lintelling over (shown in blue) but it still gets awkward and doesn't feel right to me. I was also thinking about removing some bricks from the house and sitting one end of a pair of lintels in the existing house wall.

How far could I span in pre-stressed concrete lintels when supporting normal brickwork/and low density blocks?

Are there any other approaches to this?

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• garyo
• 20 Feb 2012
• 1

Thanks

Gary

 

[^woody^]

That may be an option, but it will be at the BCO's discretion, or via an engineers proven design

The only other options are move the pipe or move the wall

 

[garyo]

Thanks Woody. Moving the wall isn't really an option, so I think I'll have to move the pipe.

Is the following solution okay for the situation : A new inspection cover over the exposed 90 degree bend, and then use some kind of coupling to join my new plastic pipe to the existing clay? Is it a problem that the existing run is encased in concrete - i.e. are there push fit couplers available so that I can expose it the run, cut it cleanly with an angle grinder, and then join to plastic?

(New bits shown in red)

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• garyo
• 20 Feb 2012
• 1

 

[maltaron]

Any builders merchant should have rubber couplers for joining virtually any pipe to any pipe. They slide over the pipe then back over the joint and fix with supplied jubilee clips.

 

[garyo]

Won't my problem be that I can't expose the existing clay pipe to get a fitting over it, so I'll have to find something that'll slide inside instead?

Not sure I'm explaining myself well - but I don't think I'd ever be able to get the concrete off without destroying the pipe, so won't be able to use a simple rubber band coupler like this:

http://www.screwfix.com/p/flexible-adaptor/19914

So need something more like this one, but as the pipes are the same diameter it won't be quite this simple:

http://www.screwfix.com/p/floplast-adaptor/42799

Do they exist?

 

[^woody^]

If some of the concrete can be removed then it may be possible to span a lintel in line with the new wall and bear one end on to the existing foundation or brickwork

Or form a wide pad below the pipe and then bridge the pipe at 90 degrees just where it crosses the wall with some small lintels, and then more lintels inline off this - but it seems you may be a bit too close to the surface for this

 

[maltaron]

Just a thought, would a straight WC connector work for you?

 

[TicklyT]

Can you replace the rest bend at the base of the stack?

Would moving the new IC to the drain near the top of your sketch, and running a new pipe straight into there be a tidier solution?

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• TicklyT
• 20 Feb 2012
• 1

 

[garyo]

Maltaron, that's a thought - something like this would be ideal. I'm not sure if they're approved for use buried underground?

http://www.screwfix.com/p/floplast-sp101-straight-connector/17227

Tickly, that'd certainly save me a bit of digging... the thing that puts me off is that at that point there are four houses waste going through so I have far less control over things. I've not done drain underground sewer work before other than soakaway work so want to be able to take my time.

I'm starting to think I could simplify the job a bit by fitting a 90 degree bend and rodding eye instead.

I can access the bottom of the stack but I'd have to get the jack hammer on the case to make a new hole through the foundations, so either way I'm in for a bit of a mess, and I didn't really want to be making a mess inside the house at this stage, which is the main thing that's putting me off moving the pipe run.

Cheers

Gary

 

[^woody^]

You can't use toilet connectors underground!

Have you actually tried breaking the concrete. It is usually possible to chip it away to expose enough of the pipe the connect to

 

[noseall]

Just a thought, would a straight WC connector work for you?

 

[garyo]

I've not tried delicately exposing it to be honest... I've jack-hammered through a couple of disused sections a few days ago but that was before I knew I'd have this challenge. Looks like I'll be giving it a go this weekend unless I can come up with a better plan.

 

[maltaron]

Thanks, Woody, for putting me right regarding the WC connector. It was just a thought.
Now, back to the origiginal post, the OP tells us 4 houses go thro' this sewer. This would mean that the local water authority owns the sewer and they will normally only allow approved contractors to work on them. This could mean a huge bill. You may be better to move the wall, allthough they are very fussy about building within 3 metres of a sewer.

 

[garyo]

The waste for the four houses all feed in to the existing manhole on the top right of the drain, so as long as I only modify my run then I'll be okay, but you're right that Tickly's proposal would mean I'd be interfering with an adopted sewer.

I've started thinking about switching to an external soil stack and then that means I won't have to jack hammer through foundations and destroy my lounge (still in day to day use). Instead I could just core drill through the upstairs bathroom wall. The downside here is that my alleyway becomes narrower by 100mm and it's already tight getting a car through.

I'm going to take a look at the upstairs bathroom routing tonight and hopefully I'll have some inspiration.