Drainage Repair - question about underground pipes

[dormermike]

Hi

Just had a CCTV survey which shows following:

Ground floor toilet to IC soil pipe is cracked underground and needs replacing

Gully cracked and needs replacing.

The issue is, there is only about 10" of room between the side of the inspection chamber and the outside of the wall where the toilet is. The toilet soil pipe disappears into the concrete floor in the bathroom and reappears at the bottom of the IC (approx depth 1m).

A drainage company are advising that the easiest plan would be to take down the side of the IC and rebuild the entire thing in precast concrete, new PCV piping easier to route properly as there is only 10inchest to play with. Caveat being they don't really know whats what until excavation.

My question is - is the toilet pipe drop of 1m likely to be inside the house (beneath floor/foundation) or should it come out of the wall at a high level and then drop down on the outside? Reason I ask is, I would plan on excavating and exposing existing so that we can get a better idea of routes, space, etc.

Thanks
Mike

 

[tony1851]

It will probably drop down the full distance inside the house.
The logic behind that would be that they would have needed fewer bends doing that way.

 

[dann09]

Something odd here.

Maybe if you posted pics of inside and outside and down the "inspection chamber" it would help?

 

[dormermike]

Hello - here you go, hope these help show what the problem is.

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• dormermike
• 16 Sep 2013
• 1

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• dormermike
• 16 Sep 2013
• 1

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• dormermike
• 16 Sep 2013
• 1

Water emptied into the gully (shower and sink) only appears in the IC as a trickle, and then a moment later comes out of the toilet outflow.

CCTV shows circumfrential cracking of the toilet pipe horizontal run at .5m and water flowing into the pipe from the crack. 0.5m is pretty much right beneath the connector in the concrete floor inside the house, but i'm not sure how accurate these things are. The water is from the broken gully, and i've removed bricks to assess the gully and basically all sink and shower water empties to ground and then eventually finds its way into the toilet pipe.

I am hopeful that this is the cause of my internal damp problem that i've plagued this board with for the past 2 years, or can't be helping at least!!

Question is how to fix it.. the brickwork in the IC seems solid so to me at least ripping it all up seems extreme, but then i also see that it is a tight position and tricky to get it right.

I did suggest to the drainage person today about a short stack to replace the broken gully, and drop a new PVC pipe into the back of the IC to replace the existing (presumably broken) clay pipe. The shower and sink could then connect into this. The gully itself is set quite deep and also is between two other gullys which capture rainwater off the roof, so i dont think this one does an awful lot besides shower and sink. Apparently taking the soil pipe through the wall into a short stack is not a good idea or wouldnt work (didnt capture reason why, perhaps falls).

This is a downshot into the broken gully:

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• dormermike
• 3 Jun 2012
• 2

Thanks

 

[dormermike]

It will probably drop down the full distance inside the house.
The logic behind that would be that they would have needed fewer bends doing that way.

Thanks - i suspected that may be the case but wasn't sure.

 

[Hugh Jaleak]

What does the plastic pipe coming into the chamber at high level serve? Looking at the condition of the chamber, (root ingress and the benching looks to be in poor condition), i'd be inclined to demolish it entirely and graft in a new plastic chamber, then replace gulley and drain to ground floor WC. Doubtful you'll be able to replace the existing pipes with the chamber in situ as there is very little room for access.

I dont see any reason why a new soil connection for the WC couldnt be run externally, with an access bend to take it through the wall to the pan position. However the existing plastic pipe would need to be rerouted to connect into any new chamber at appropriate level.

 

[dormermike]

The roots are just at the top and are old/dead I think, appreciate your thoughts though, especially interesting that you comment the benching is in poor condition.

The high level pipe which is pointing the wrong way is a gully for guttering from the roof, so rainwater.

I wasn't sure what your last sentence meant? All existing for toilet is clay not plastic.

 

[dann09]

Thanks for the pics.

1. I think that your original ground level(GL) was the approx. top of the gulley.
From what i can make out, the GL has since been built up say, 8" - 10" above the original level.
This might be your source of internal damp, the bridging of the DPC.

2. Do you have a DVD copy of the camera investigation?

3. Could the shower and sink wastes be teed into one waste?
This pipe would then come out of the wall and turn right to drop into the rainwater gulley you say is there?
The fractured gulley could then be eliminated.

Is the pipe that comes high into the left hand side of the MH draining a rainwater pipe/gulley?

4. Lacking a pic of the WC, might it be possible to tee-in the combined waste to the WC soil pipe, or a WC pan connector with a 40mm boss - depending on materials and floor.

5. Or dig out and see whats what? From the cover you could easily reach down into the MH where necessary.

6. The "difficulty" will be locating the crack and replacing the pipe - if its in the foundation then brickwork will have to be removed. How it enters the MH is a wait & see.

 

[Hugh Jaleak]

To clarify, should you install a new plastic chamber, then the pipe coming into the current chamber at high level would need to be rerouted. However, if it's for rainwater then should be fairly easy to alter as required.

Should a new chamber be installed to replace existing then I cannot see any reason why a new connection cannot be provided for the ground floor WC, run externally to the house wall, with a 90deg access bend at the top to turn the pipe through the wall to connect to the WC. Existing (defective) drains could then be mothballed and sealed off.

 

[dormermike]

Thanks for the pics.

1. I think that your original ground level(GL) was the approx. top of the gulley.
From what i can make out, the GL has since been built up say, 8" - 10" above the original level.
This might be your source of internal damp, the bridging of the DPC.

I've considered and discounted that - the external and internal DPC course is visible and at on the outside is around 5-6 inches above ground level. Exterior skin was rebuilt in 1990's. The external ground level no doubt lower previously than now but i doubt it was that low, as i can see the foundation next to the gully pot- if anything the gully looks too low. Never know though, i guess.

2. Do you have a DVD copy of the camera investigation?

Yep: https://www.dropbox.com/s/bfpxhw6kpzoagdr/MH4_to_toilet.wmv

3. Could the shower and sink wastes be teed into one waste?
This pipe would then come out of the wall and turn right to drop into the rainwater gulley you say is there?
The fractured gulley could then be eliminated.

Is the pipe that comes high into the left hand side of the MH draining a rainwater pipe/gulley?

Yes thats right

4. Lacking a pic of the WC, might it be possible to tee-in the combined waste to the WC soil pipe, or a WC pan connector with a 40mm boss - depending on materials and floor.

5. Or dig out and see whats what? From the cover you could easily reach down into the MH where necessary.

6. The "difficulty" will be locating the crack and replacing the pipe - if its in the foundation then brickwork will have to be removed. How it enters the MH is a wait & see.

Yep thats pretty much as i understand it, dig and see whats what. Am getting 2-3 quotes in.

 

[dann09]

Thank you for the replies and the vid. Trouble with the vid was i had no context but there was a definite circular crack, and possibly some hairline lengthwise cracks.

Were we in two different drains? I couldn't make out the possibly two different flows.

If there is a suspicion of one drain somehow cross connecting into another drain ie. your gulley drain emptying into your WC drain, then coloured water can be used to ID whats going to where.


FWIW: if there is ever a next time drain camera requirement, then perhaps you will hire a colour and commentary camera with a seconds timer.

You could dig out to reveal pipes from wall to MH yourself.
Keep the MH & gulley covers on as a rat precaution.

You could temporarily extend & run the shower & basin wastes somewhere else to the right hand.

Holdfire on opening up or demolishing the brick MH.

Do you have another WC?

Still no pics of the interior/WC?

 

[dormermike]

Yes two diff drains, first the toilet then the gully. Sorry should have pointed that out.

The was a pro survey btw, I don't have the gear.

The gully is definitely crossing over into the toilet, no question.

Toilet is boxed in, its a typical arrangement where the soil pipe goes into the floor. Not sure a pic would show anything useful?

 

[Hugh Jaleak]

Bit concerned about that Circumferential crack in the WC drain at around 2 minutes into the survey, does seem to be a lot of water getting in there. Appreciate the gulley and associated drain is in poor condition, but a gulley is only taking water when an appliance draining to the gulley is discharged. That water has to be coming from somewhere.

Drains need to be fixed, but it could also raise the question of a leaking water service pipe. Judging by the drainage, the age of the property would indicate a lead water service, (and even if the original has been replaced there's no guarantee the old service was disconnected before being abandoned.....) Think without digging it up to see whats going on and the amount of water involved then it's difficult to say further, but certainly wont be the first time an old lead service has been merrily leaking away for many years!

 

[dormermike]

Hi Hugh

I've wondered about that too - the sink was running which was emptying into the gully, which then finds its way into the soil pipe. The bit i find concerning is the movie shows the distances as .5m from the IC which if I read correctly is actually underneath the house, so i'm not entirely clear how the gully water is tracking back underneat the house before leaking - it must be collecting in order to squeeze through that crack too.

The other thing i was concerned at was what seems to be a "drop" of the pipe just after the bend - again, that would be directly underneath the floor i think.

Incoming main is blue plastic pipe, replaced in 1994 and confirmed by WB as not leaking. If a incoming main was still leaking (intriguing possibility!) water would be coming into the IC constantly, which its not - so i'm pretty sure the gully is where that water in the movie is coming from.

Thanks again.

EDIT: basically shopping for quotes at present and resigned to a rather large bill. Be good to get it fixed though, as i'm pretty sure this is responsible for most if not all the damp - solid concrete floor, damp around edges in gap between wall floor junction, and random dampness in mortar (black) in internal walls, adjacent to this issue. Ironically the bathroom floor seems dry.

 

[noseall]

I'd hire a micro digger (if accessible), dig the lot out and start with a plastic chamber and re-hash the lot.

Drainage would be back on in a day and all making good finished off the morning after.

Repairs may be ok but could be unreliable.

The high level pipe looks like a modern addition and is probably a storm run off. Have had the lid off when it is raining?