Can I reduce the number of holes in wall for plumbing waste pipes?

[Matt K]

Hi,

I'm renovating my old (Victorian terrace) house, putting a bathroom in a room at the top at the back of the house. In doing so I need to run some pipework for waste water etc out through a wall to the stack.

We will have 2 sinks, a washing machine, toilet (so overflow), boiler, bath and a shower in the room. Considering all of that, there's potentially 6 waste pipes that would need go into the soil stack (assuming I combine the sinks) out through the wall at the floor level. I'm a bit concerned about putting that many holes into the wall at the level where the floor is attached.

My questions is, is it OK/possible to combine the waste water pipes under the floor, in the room before they go out through the wall, so that I can reduce the number of holes I need to make in the wall? One person I've spoken to has mentioned I could use Durgo valves to help with this but I wanted to check before starting any work if it's the right approach/ thing to do.

I've attached an image fo the room with the outside wall labelled incase that helps answer. I'd also be in interested if anyone (probs easiest if in London) would take on a day's work to come up with a pipework design? But mainly interested in answer to the question above first!

Cheers, Matt

 

[John D v2.0]

You can run them all into a 110mm waste pipe indoors with the WC, then through in one.
Or run all the 40mm pipes into one 50 and run that through separate from the WC

 

[Nige F]

Can you show the position of the stack ? Why a washing machine, no room in kitchen presumably ? Noisy on a top floor. Where in London ?

 

[Matt K]

Thanks John D, so I think we'll go for:

Waste pipe A through wall
Which inside room combines Sinks, Toilet overflow, boiler condensate/overflow. So 3 waste pipes (which will almost never be used simultaneously) together

Waste pipe B through wall
Which inside room combines Shower & Bath (+bath overflow)

WC waste through wall (less of an issue a little above floor level

Washing machine waste pipe through wall (again, less of an issue as will be up wall, above floor level)

@ Nige F - The position of the stack on the outside wall may well change (based on what we're doing with the ground floor), I have updated the diagram with where I think it's most likely to go.

The washing machine going up there is because we're considering separating the house for our parents to live in with us (but still have a bit of privacy!). And what will be the kitchen will be a bit space constrained.

We're in Brockley, South East. You?

Cheers, Matt

 

[John D v2.0]

So 3 waste pipes (which will almost never be used simultaneously) together

Remember, the issue with combining waste pipes is not so much whether they will be used together, but whether they will pull the traps of each other. Hence my suggestion for 50mm pipe (laid to the correct fall).
However your comment about AAV will also work, but generally if you can get away without it will be simpler.

You should be especially cautious if there's a boiler involved to make sure there's an adequate air break via the SVP or otherwise, as pulling the trap on a boiler has safety implications.

 

[Matt K]

Sorry for the basic question, but when you say "pull the traps of each other"... Does that mean wash water from what was past the trap, back to the other side, creating smell etc in the room? Or something else?

I wonder if it'd be safer to keep the boiler waste/overflow etc separate? 3 holes at floor level is still a lot better than 6 which is what I was worried I had to put in at the start!

Cheers for the info, and appreciate the patience explaining stuff!

 

[Tigercubrider]

Many toilets now overflow into the pan, so that's one down.

 

[John D v2.0]

That means the water leaving one appliance fills the bore of the pipe, causing low pressure upstream of the water. As it falls down the pipe, air has to enter the system somewhere to replace it, either from a vent pipe, aav, or by pulling in air through the easiest trap.
If the trap is pulled, the water can be low enough to let air and other gases pass until the appliance is used next.

 

[Hugh Jaleak]

Exercise caution if putting bath and shower on same waste. Have seen it before, the waste pipe bunged up and the contents of the bath reappeared in the shower, overtopped the tray and flooded the bathroom and kitchen below.

 

[Matt K]

Thanks for the tips on this one so far.

I'm just getting around to doing the pipework, should happen next weekend I think. With the point about pulling traps in mind, does anyone have any advice on how I can design the pipework to avoid the issue of pulling the traps of connected waste water pipes?

It seems like I can(?) combine the sinks, toilet overflow & boiler condensate/overflow into one 50mm waste pipe that then goes through the wall (to reduce the number of holes). Do I need to have durgo valves, or something similar, on each waste pipe above the point at which they join maybe? Could this avoid the potential issue with the boiler?

I could draw up a design on a bit of paper and post a pic for comments, if that'd be any use? Any advice would be really appreciated!

Cheers, Matt

 

[dilalio]

You need to speak to Building Control as this work is notifyable. Discuss your plans with them and they will appraise.

 

[Matt K]

Understand that the work is BC notify-able, our building officer is a good guy and we've had him onboard for most of the work already. He's previously mentioned that he's happy to review plans/drawings and give feedback, it's coming up with those plans/designs that I'm working on now. In doing so, it'd be good to hear if there are any specifics around what needs to be done to avoid pulling traps of other connected waste pipework?

 

[Nige F]

Use Hep V O waste valves instead of traps - apart from the shower.