Waste pipe plumbing question

sourpuss2021

I'm revamping my kitchen.   The room is in a top floor flat in a converted house.   At the moment the kitchen sink is in an alcove on the left-hand side of the room. The waste pipe goes through the wall to the soil pipe.  The condensing boiler is also connected to it.

I want to move the kitchen sink to the right hand corner of the room.    This will be easiest in terms of having the sink, washing machine and dishwasher next to each other.  There are already hot and cold inlets there that can be used. 

However I've just realized that I will still need the condensing boiler to be connected to the waste!    So, will it be possible for the waste that goes through the wall to be fed from both directions?  So it is getting the boiler from the left, and the sink, washing machine and dishwasher from the right. 

Here are photos which might make it clearer.   I do have a plumber in mind but don't want to be asking him to do something impossible!

Section62

sourpuss2021 said:

So, will it be possible for the waste that goes through the wall to be fed from both directions?  So it is getting the boiler from the left, and the sink, washing machine and dishwasher from the right. 

You shouldn't do it if it means using a standard tee with the wastes arriving at the tee in opposing directions - there's a risk of backflow and blockages with that method.

I would stick with an elbow where it currently is going through the wall, but facing in the direction of the new sink.  Then bring the boiler condensate pipe along the wall at a higher level than the waste pipe and drop it into the waste pipe from above, via a tee (i.e. with the 'side' branch pointing upwards).

That way there is no risk of gunge from the sink and appliances blocking the condensate drain pipe.

sourpuss2021

Thanks, Section62, that's very helpful.   I'll show that to the plumber.

There's also another waste pipe buried somewhere halfway up the right-hand wall, which feeds into the soil pipe at a slightly higher level.  The reason for this is that the flat is slightly split level.   This pipe comes from the bathroom sink which is round the corner up half a dozen stairs. The plumber had suggested he could drill into the wall and connect the sink etc into this pipe.  However that would be a big and messy job as it is a very solid and deep brick wall.  

If there's a solution that doesn't involve having to reach this pipe it would definitely be preferable.    He also mentioned putting a standpipe in on the right-hand wall.  I  think that would do the same thing as you describe by stopping a backflow.

Here's a photo, the buried pipe from the bathroom sink is the one on the right-hand side with the cap, with the bath coming in from the left.

FreeBear

Section62 said: I would stick with an elbow where it currently is going through the wall, but facing in the direction of the new sink.  Then bring the boiler condensate pipe along the wall at a higher level than the waste pipe and drop it into the waste pipe from above, via a tee (i.e. with the 'side' branch pointing upwards).

And the condensate pipe only needs to be 15mm or so rather than full bore 32/40mm. Should be easy enough to route round the wall at a high enough level.

Section62

sourpuss2021 said:

If there's a solution that doesn't involve having to reach this pipe it would definitely be preferable.

I agree.  There's no point in digging around in a wall looking for a pipe if there is an easier alternative.  Also, it is poor practice to bury waste pipes in walls, and very poor practice to bury waste pipe fittings in walls. If they leak then you won't know until damp patches start appearing on the decoration.

Given the split-level arrangement I think it would also make sense to keep the two waste installations separate until they reach the 110mm stack.  If there were some kind of blockage or overflow you don't want the waste from the higher level flooding out into lower-level rooms.

sourpuss2021

Thanks both, that's very helpful to know!

There is 22cm space between the bottom of the sash window, and the top of the waste pipe that goes through the wall.  So the condensate pipe could go along there and drop down.   It wouldn't be possible to have a larger gap however because of the big and low window.

The bathroom sink waste pipe already habitually clogs up with soap suds & bristles, & has to be blasted clean with the cap taken off where it meets the soil pipe.  So yes definitely best to leave it alone.

I'll get the plumber round and repeat to him what you've said.

Section62

sourpuss2021 said:

There is 22cm space between the bottom of the sash window, and the top of the waste pipe that goes through the wall.  So the condensate pipe could go along there and drop down.   It wouldn't be possible to have a larger gap however because of the big and low window.

If I've understood what you need correctly then it would look something like this rough image -

 - the elbow going into the wall is solvent weld, so the plumber may need to replace it rather than rotating it (it depends how tight it is in the wall and what happens outside), but otherwise it should be a simple and straightforward job. (the waste pipe on the left is removed as well)

sourpuss2021

Hah, thanks so much for the diagram Section62!   That looks like a good solution.   

And a joiner will be coming at some future point to do some elegent boxing-in, so it should be quite hidden when it's all finished .

Bendy_House

Hopefully that will work out.

A concern is that the pipe is already quite high where it exits through the wall, and the existing pipe from the sink seems to have just enough fall in it. If the new sink position is further away from this exit, then it's likely that the fall will also be less. Perhaps not enough. Your plumber can probably help this by fitting the sink's waste pipes as far up close to the sink bottom as possible - there's hopefully an inch or two available there, and perhaps using a slightly less deep U bend.

Anyhoo, your plumber will know.

sourpuss2021

I felt an MSPaint craving so I made a new version of the diagram.  I will show it to the plumber.  He may think, "Why are you showing me this, I'm a plumber!"  But he does have a habit of turning up without any of the parts that are needed (and too busy on other jobs to engage with much dialogue beforehand).   So I will probably need to get the parts in myself first.

Thanks Bendy_House for that further point.  

Here is another photo.  The hot water inlet is there next to the cold, it just needs reconstituting from under the floorboard where it was capped off. 

Oh and yes, there's also a radiator to be removed.   He only put this in a couple of years ago, it will be moved to the opposite wall.   Then the sink will be in this right-hand corner.  

I think the plug socket can stay (handy for the washing machine) but if it's not allowed to have one under a sink then the electrician is due to come round beforehand and can remove/move it.  

Thanks again for your help!

FreeBear

sourpuss2021 said: Oh and yes, there's also a radiator to be removed.   He only put this in a couple of years ago, it will be moved to the opposite wall.   Then the sink will be in this right-hand corner.

Have a look at plinth (kickstrip) heaters - Easy to plumb in, and they kick out heat at floor level. Not particularly cheap, but worth it if you want to save wall space.

Sockets under the counter should have an isolation switch above (in my opinion). When hidden inside a cupboard, they can get hidden by the assorted "stuff" that accumulates.