Moving or removing a toilet stack

[jocollett]

Hello, hope someone can help with this one.

We need to move our upstairs toilet to another wall in the bathroom to make way for a bath. We won't be able to reach the existing toilet stack as the pipe would need to go round the house and a roof drain pipe and garden room roof would be in the way. I can see two possible solutions but not sure if either are possible.

In either case I want to remove the old stack as only the washing machine would run into it (which I can move) and I can then take the stack out of the garden room. Sink and bath washbasin etc go into hoppers or gullies.

Option 1
It's in a 50's excouncil house and the old loo was downstairs under the bathroom. The old pot sewer pipe is still there so would it be possible to take the soil pipe down through the bathroom floor internally and under the kitchen floor and connect to the old poo pipe. If I did this, could I simply vent the toilet with either an Air Admitance Valve next to the toilet or send a small bore pipe out though the wall to vent outside. All the research I have done suggests I need a proper stack but this seems over the top and unnecessary.

Option 2
Make the rainwater drainpipe from the roof into a toilet stack and convert the gully into a sewer with inspection chamber and send the loo pipe into this with bath, sink and roof guttering also.

Thanks for any advice

 

[Hugh Jaleak]

Firstly, this work is notifiable to the local Building Control Department at the council.

Option 1. Should be able to connect internally to the old pipe for downstairs loo, but it is likely you will need to continue upwards through the roof to vent the stack. Building regs require this, without it the work will not be passed by building control, and the vent is there for a reason, to ventilate! Air admittance valves are allowed provided the drain is vented elsewhere, but as you are doing away with the existing then you would need to provide an alternative.

Option 2. Its possible the rainwater may discharge into a storm sewer, foul water (from toilets, sinks, etc.) is NOT allowed to be discharged into this system. The toilet and sink etc. will discharge into a separate foul sewer.

Option 3! Excavate and locate where the existing pipe to former downstairs loo enters property. Connect to this outside the property and run new external stack to take upstairs loo, and continue to vent at roof level. Could connect basin and bath wastes into this too, and do away with the hopper arrangement.

 

[jocollett]

Thanks Hugh it's good to know option 1 is possible. With some fiddling I could just plumb the sink and bath into the new internal toilet soil pipe with vent/stack going up above and keep BC happy. Could I plumb the sink into the bath pipe and then just run the bath pipe into the stack, or would they need to go in separately.

Regarding venting, I thought the system would vent itself through the two gullies the rain water and kitchen sink run into. These aren't sealed so if sewer gases build up surely they would just seep out of these. Why don't these make toilet stack vents redundant? I don't understand this bit. javascript:emoticon('')

The old internal soil pipe is just inside the wall from the drain pipe gully and both connect together under an inspection chamber a couple of feet away outside. This is why I thought option 2 would work. Could I get away without a new inspection chamber if I changed the gully into a soil/sewer/stack arrangement. It would need to go around a corner before reaching the existing inspection chamber.

Option 3 is a good idea but would be on the same wall as the existing stack and so the bath and garden room would still be in the way.

I hope I can explain all this to BC. I have a railway sleeper lintel problem to discuss with them too. javascript:emoticon('')

 

[Hugh Jaleak]

Sink and Bath can go into common pipe, but it would be advisable to use anti vac traps, this will ensure traps doesnt get sucked out when another appliance is discharged, letting foul air into the room.

Gullies will have a trap in them, same principle as sink trap, to prevent foul air from the drains causing annoyance. It is for this reason the stack needs to be vented, it allows the drain to 'breathe' with foul odours being released at roof level where they wont cause a nusiance.

Any amendments to the existing system will require Building Control approval. Without actually seeing the site and layout its difficult to ascertain exactly what you propose to do, and what is/is not permissible. It may be worth speaking to the BCO regarding your intentions, he will advise on what he wants to see done. Just to note, there should be a means of access to all points of the drain, manholes are usually required where the drain changes direction.

 

[jocollett]

Thanks for clarification about gullies, I understand that now and for tips for anti vac traps.

Just spoke to building control and they said I would need to keep the existing gully for the rain water and that although I could run a stack internally it would be advisable to do it outside in case it leaked, which is a good point i suppose.

So I'll probably run a new toilet stack and fit a new inspection chamber where the bend into the old sewer pipes will be and join the rainwater at this point too. Only problem with this is that it would be directly outside the garden room door. Do you know if there any restrictions as to how close inspection chambers can be to your house?

I appreciate it's hard to visualise from my description, ill try scan a plan in to make it clearer.

Thanks again Hugh

 

[Hugh Jaleak]

I dont know of any restrictions on having inspection chambers close to the house, you can have them inside the property provided a suitable sealed cover is fitted!

A properly installed stack will not leak! (Not sure why they said that!) The 1965 building regs required all stacks to be fitted internally, until a later amendment rescinded this and allowed external fitment again.

Building control may insist you keep, (or resite if you need to), the existing gully for the rainwater discharge. This could be connected to a seperate system for surface water drainage, so connection of a rainwater pipe to your new inspection chamber would not be allowed. Connection of rainwater pipes to foul sewers is only permitted as a last resort now, and only then if no surface water drains are available and the ground is unsuitable for a soakaway to be built.

One point from your first post. You wish to remove the exisiting stack from the garden room. You could utilise the drain here to accept the current washing machine waste. Either fit a new stub stack, (probably unsightly though) or fit a gully with a sealed lid. (Couple of options that may prove easier for you than resiting the washing machine!)

 

[jocollett]

Thanks again Hugh for all this advice. I've realised there is a 5th, simpler option, although it means leaving the existing stack in the garden room. I can move the bathroom door about 15cm within the stub wall and therefore fit the bath in at right angles to where i was going to put it. This means I can put the new toilet on the same wall as the existing one, with the sink next to that. Should be a lot easier than getting BC involved with their fee's and sorting out a the new stack.

 

[Hugh Jaleak]

Sounds like a plan! Drainage and stacks aren't cheap to fit, and a lot of upheaval while you do. Glad you've got it sorted.