Getting a long kitchen sink waste across and out to main waste stack

[thedukewood]

I have a project where we'd like to put a kitchen in the living room to create an open plan. The would mean the sink waste running the length of the kitchen circa 3m and then circa another 3m to get out to the waste stack. Most joists run the right way ( subject to any noggins) however we'd need to get across approx 1.5m from sink to get to a straight run out which would mean going though joists.

Is there any way of doing this please? I have seen other very similar flats that have achieved it but can't work out how.

Many thanks

 

[ShaunCorbs]

Drilling them ?

 

[thedukewood]

Drilling them ?

yes - could drill the joist but wondering if building control will want 50mm pipe and even if 40 mm thought there were rules about how much you can take out of joists etc thanks

 

[ShaunCorbs]

Depends how deep they are as it’s 1/4 max hole through the centre so an 8” joist you could do 2”

 

[Knappers]

Yes, and needs to be through centers which causes an issue with getting a good drop over any distance. Holes should be kept to correct zones. You'd be alright getting to outside wall in 40mm but I'd consider going up to 50 for second part of run and an anti-vac trap on sink.

 

[Timmy D]

I’d want minimum 25mm drop per meter. Ideally 2” all the way and vented.

If it’s not vented, building regs won’t even allow 2” for that distance.

If you need to run it in 1.5”, and if there is going to be dishwasher/washing machine, perhaps consider a second dedicated run for them.

 

[thedukewood]

I’d want minimum 25mm drop per meter. Ideally 2” all the way and vented.

If it’s not vented, building regs won’t even allow 2” for that distance.

If you need to run it in 1.5”, and if there is going to be dishwasher/washing machine, perhaps consider a second dedicated run for them.

no Dishwasher only sink so that's all good. Do you think they would let me run in 32mm if I can't can't that diameter hole in joists ie: if they not 200mm? In principle I could run get into 40mm as soon I across room and between joists so could even to go 40 from sink across back of kitchen - reduce to 32mm ( about 1.5 m through joist ) and then go to 40/50 out to stack. And vent sink. ps I am off to see if I can get board up quickly to check the joist depth a bit later thanks

 

[thedukewood]

Yes, and needs to be through centers which causes an issue with getting a good drop over any distance. Holes should be kept to correct zones. You'd be alright getting to outside wall in 40mm but I'd consider going up to 50 for second part of run and an anti-vac trap on sink.

thank all. Please can you explain what you meant " correct zones"

 

[Knappers]

Would need to check to be sure bit I think holes should not be in middle or edge of joist, should be in 0.25 - 0.4 of joists span.
Notches go in first 0.25 of joist span but not right at edge.

I couldn't say that 1 1/4" (32mm) would be ok, it's definitely grossly inadequate for regs.
It would probably work - atleast for a while.

You could run across wall if no doors in way or through floor and box in at ceiling level downstairs?

 

[Timmy D]

Get the correct sized pipe in, as once it’s in and floor is down, when (not if) it regularly blocks, you’ll be kicking yourself.

If needed, reinforce the joists. Use some steel if needed.