repositioning soil pipe in a Victorian terrace

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I want to move the kitchen and bathroom away from the exterior and need to relocate the soil pipe to the middle of a Victorian terrace house. There is a manhole at the front of the house and the existing soil pipe is right at the back of the house (and rusted through). Drawing a straight line between the manhole cover and the soil pipe, I think the drain goes under some open ground about 3m from the new position for the soil pipe (also about 3m from the old soil pipe) before it goes under the rest of the house.

1. Do I dig a new manhole to join the new soil pipe into the existing drain?

The ground floor will be up, so I have a chance to repair any damage to the existing drain under the house (there is a LOT of rising damp).

2. Can I bend the vent around joists and rafters above the highest drain into the soil pipe?

3. Would I need to put an inspection plate in the soil pipe between the highest drain and the lowest bend?

The new kitchen sink, basin and toilet will all be with 1m of the soil pipe. The bath drain will run about 2m.

4. Given that the runs are so short, should I have separate drains from basin, bath and kitchen sink into the soil pipe?

5. Is it easier if these are on the other side to the toilet?
 
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1. Do I dig a new manhole to join the new soil pipe into the existing drain?
You would treat any new connections the same as if it were out doors, only with air tight screw down recessed manhole covers. So if the junction is not roddable from upstream then you may need to build an chamber internally

2. Can I bend the vent around joists and rafters above the highest drain into the soil pipe?
There is no problem with excessive bends in a (foul air only) vent pipe.

3. Would I need to put an inspection plate in the soil pipe between the highest drain and the lowest bend?
It depends upon the nearest rodding point. If access is difficult, i.e. an inspection chamber is some distance away then yes, you may need to fit an access collar.

4. Given that the runs are so short, should I have separate drains from basin, bath and kitchen sink into the soil pipe?
Each item (bath, basin, sink etc.) should have its own 32mm or 40mm pipe run to the stack or gully otherwise the traps may siphon or gurgle. There is no need to take 110mm drains to each item though.

5. Is it easier if these are on the other side to the toilet?
I'm not sure i know what 'other side of the toilet' means. Do you mean upstream or downstream?
 
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1. Do I dig a new manhole to join the new soil pipe into the existing drain?
You would treat any new connections the same as if it were out doors, only with air tight screw down recessed manhole covers. So if the junction is not roddable from upstream then you may need to build an chamber internally
The nearest connection point is actually 3m away outside.

3. Would I need to put an inspection plate in the soil pipe between the highest drain and the lowest bend [ of the vent ]?
It depends upon the nearest rodding point. If access is difficult, i.e. an inspection chamber is some distance away then yes, you may need to fit an access collar.
The soil pipe would be shared by 2 flats. The bottom elbow would only be 3m from an external manhole.

5. Is it easier if these are on the other side to the toilet?
I'm not sure i know what 'other side of the toilet' means. Do you mean upstream or downstream?
I can position the toilet to the right hand of the soil pipe and all the bath/basin/sink on the left hand side of the soil pipe.
 
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I would check the existing manhole at front is a foul sewer. Could be wrong, but I have never come across a property of that age with drains running under the house. Usually the Victorians housed the toilet right at the back of the house, or even away from the house in the rear yard! The foul drain may run along rear of the properties, I would determine where the existing stack connects to initially.

You cannot connect a waste pipe into a stack within 200mm below the centre of a W.C. branch connection, unless using a manifold. Bath and basin wastes could be combined for ease of installation, but anti vac traps, or Hep Vo valves will prevent any syphoning of traps. Sink needs its own waste, likely a washing machine would be connected too, so run a separate 40mm to stack for this.
 
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I would check the existing manhole at front is a foul sewer. Could be wrong, but I have never come across a property of that age with drains running under the house. Usually the Victorians housed the toilet right at the back of the house, or even away from the house in the rear yard! The foul drain may run along rear of the properties, I would determine where the existing stack connects to initially.
Every house in the terrace has a drain manhole in the small front garden, which is why I suspect the foul water drain is at the front of the house. This surprised me too. I'll check the surveyors report.

You cannot connect a waste pipe into a stack within 200mm below the centre of a W.C. branch connection, unless using a manifold. Bath and basin wastes could be combined for ease of installation, but anti vac traps, or Hep Vo valves will prevent any syphoning of traps. Sink needs its own waste, likely a washing machine would be connected too, so run a separate 40mm to stack for this.
I guess I'd probably be looking at a manifold for connecting toilet (110mm) and bath (40mm). Above that I would need separate 40mm sink connection below a 32mm basin connection (on the same side). I was going to tee the washing machine into the sink waste.

I see Wickes sell an Internal Soil Air Admittance Valve (product code 431971). Would that allow me to vent into the loft?
 
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Assuming you are getting the work approved under building regs, then it may be the Building Control Officer will ask for the stack to be vented. (It is supposed to be at the head of the drain.) An internal AAV should be ok in a loft, biggest issue is with them freezing up when installed externally. External versions are available but at extra cost!

Any connections above W.C. branch are fine, the concern is with wastes below, as discharge from the W.C. can crossflow into them, hence the 200mm below no connection zone.
 
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Exellent answers, Hugh. But to prove the exception to the rule ;) I`ve seen a couple of Viccies with drains front to back. Did wonder about the wisdom of it though :confused: Probably down to cost even then.
 
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It is supposed to be at the head of the drain.
I've since read that I'll need an external (exhaust) vent as well. Maybe I could also repair the original external soil stack as a vent, which runs straight up a flat gable end. It might be cheaper than running the new stack through the roof.
 

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