Soil stack arrangement for ensuite, kitchen & utility

[SimonD]

I've hit a brick wall inside my head and every time I read Approved Document H I find my eyes glazing over. I'm sure the solution is more simple than my mind is telling me so I thought I'd put this out here. Ideas and suggestions welcome please.

 

This is all retrofit with some annoying limitations. I'm trying to figure out the best way to deal with the waste from new ensuite, utility and kitchen. Ensuite and utility are on the ground floor. Kitchen is above the ensuite. Waste from kitchen will only be from dishwasher and sink.

 

The drains are all existing and shallow clay pipes. The manhole sits near the soutwest corner of the house. From this I have a drain going halfway along the west face of a house terminating in a soil stack. This deals with waste from 2 bathrooms. I then have a drain extending 3/4 the length of the south wall which has a gully and then terminates in what used to be just a soil vent pipe. I need to get rid of these as they're too close to the house wall and get in the way of the external wall insulation. This bit it fine as I'll replace with new ones.

 

Ideally, and because the drains are already vented to the other side of the house I'd like to plumb the ensuite straight into the drain (layout for all this works fine). The utility would feed into a gully. In the kitchen I've got about 3.6m height to drain invert.

 

My question is around how to deal with the waste from the kitchen. I really don't want to have an additional exterior soil stack for this as this would cause problems around windows and a bridge extending out from the 1st floor of the house - and it would look very ugly. Photo attached shows the south face where the kitchen is upstairs on the right hand side of the house. External soil stack would come up between downstairs back door and window to the right. I can at a push install the soil stack internally and bring it up to kitchen level or there is decent space to bring an external soil stack up to the bottom of the bridge and install with aav (this would terminated less than a meter below the highest point of any kitchen waste).

 

So, in this instance, do I have to install a soil stack and/or is there a clever and neat way to bring the kitchen waste water down that I'm currently blind and ignorant to?

[Temp]

16 minutes ago, SimonD said:

Ideally, and because the drains are already vented to the other side of the house I'd like to plumb the ensuite straight into the drain (layout for all this works fine).

 

That may or may not work. When you flush the rnsuite WC it might syphon water from the ensure basin or other traps. The cure might be to add an AAV to/near the affected trap.

 

21 minutes ago, SimonD said:

My question is around how to deal with the waste from the kitchen. I really don't want to have an additional exterior soil stack for this as this would cause problems around windows and a bridge extending out from the 1st floor of the house - and it would look very ugly. Photo attached shows the south face where the kitchen is upstairs on the right hand side of the house. External soil stack would come up between downstairs back door and window to the right. I can at a push install the soil stack internally and bring it up to kitchen level or there is decent space to bring an external soil stack up to the bottom of the bridge and install with aav (this would terminated less than a meter below the highest point of any kitchen waste).

 

AAV must be higher than the kitchen waste. If it helps .. I don't think a stack for water only has to be 110mm. I think 82mm is the minimum?

 

If I've understood  the layout... Can you install an external stack just around the corner on the east face? Then run a drain from that along the south wall picking up the ensuite as you go past.

[SimonD]

8 hours ago, Temp said:

 

That may or may not work. When you flush the rnsuite WC it might syphon water from the ensure basin or other traps. The cure might be to add an AAV to/near the affected trap.

 

 

AAV must be higher than the kitchen waste. If it helps .. I don't think a stack for water only has to be 110mm. I think 82mm is the minimum?

 

If I've understood  the layout... Can you install an external stack just around the corner on the east face? Then run a drain from that along the south wall picking up the ensuite as you go past.

 

Thanks for that. Good suggestion on moving the stack to east face wall. I've dug out around the existing drains today and it's so shallow that when calculating for a 1:80 fall the crown of the pipe will be no more that 25mm below ground level once round the corner.

 

What I have thought is that about 2.6m downstream of the old vent stack is a junction that went below the walls to serve an old loo as per photo below. I was going to replace this with a straight drain section. Now I'm thinking I might just plumb the drain through here and run a pipe horizontally under the floor to the ensuite and then up to the kitchen internally. Hope that makes sense.

[Temp]

1 hour ago, SimonD said:

Thanks for that. Good suggestion on moving the stack to east face wall. I've dug out around the existing drains today and it's so shallow that when calculating for a 1:80 fall the crown of the pipe will be no more that 25mm below ground level once round the corner.

 

Is that based on the depth of the manhole at the south west corner? 

 

One problem is that a stack should have a large radius bend at the bottom. If the pipe is only at 25mm below ground then virtually all of that bend would be above ground. I suppose if its only serving a kitchen a normal radius bend might be allowed. Will have to see what your BCO says.

[SimonD]

13 hours ago, Temp said:

 

Is that based on the depth of the manhole at the south west corner? 

 

One problem is that a stack should have a large radius bend at the bottom. If the pipe is only at 25mm below ground then virtually all of that bend would be above ground. I suppose if its only serving a kitchen a normal radius bend might be allowed. Will have to see what your BCO says.

 

Yes, it is. I'll have to have a chat with BCO as it now looks like any amendments won't be to regs and if I've got to dig new drains to correct dpeth, I'd have to install a pump because the mains is 8 meters into the hill behind the house.