Soil Stack Connection WC Bath

[Flibblewibble]

Afternoon,

I’m having an issue with some plumbing (not my own). Attached is the soil stack with Wc, sink and bath connections (AAV at top).

When the WC is flushed the bottle trap under the bath gurgles a lot and possible loses water (or gains it from WC ). We have had the smell of foul drains coming through sometimes. There is only a bottle trap on the bath and then about 2.5m of 40mm pipe work round a right angle into the stack.

Is the location of the bath waste legitimate opposite and below the WC connection? Or have the plumbers contravened regs? Common sense suggests it is daft… Is there any correction for this that is simple. The whole stack setup is now hidden away behind a beautifully tiled shelf.

Thanks in advance for your thoughts!

 

[Wayners]

Stack vented through roof outside?

 

[Flibblewibble]

Stack is not vented through roof at this point. It’s just on the AAV half in shot at the top of the photo. There is a vent to roof on another stack in the house.

 

[Wayners]

That could be your problem. Will not be helping. Take air admittance valve off and see how things work out just as a test.

 

[Hugh Jaleak]

Bath connection contravenes Regs, (https://assets.publishing.service.gov.uk/media/5a80cf9ded915d74e33fc8ae/BR_PDF_AD_H_2015.pdf), which advise any opposing connection within 200mm of the centre of the WC Branch.

Situation could have been avoided using a soil manifold, as it its possible the WC flush is swamping the Bath connection thus drawing the trap.

 

[Flibblewibble]

Thanks Hugh,
This is what I feared as the plumbers have done some other bits that also seem wrong, such as an under sink manifold which sits at a lower level than the output pipe from its p-trap.

 

[Hugh Jaleak]

Thanks Hugh,
This is what I feared as the plumbers have done some other bits that also seem wrong, such as an under sink manifold which sits at a lower level than the output pipe from its p-trap.

Photo? Can advise better if we can see the issue.

 

[Madrab]

What were they thinking, such a school boy error, obviously the outflow from the toilet is going to impact on the bath waste. In fact it probably couldn't have been placed any worse for it then to be impacted by the outflow from the toilet, as suggested by swamping and causing a pull on the wastepipe/trap, or even worse, if the bath waste is the right depth into that boss, crossflow, that could then drive foul waste water up into the bath waste run.

Simple fix - 'fraid not - stack needs split and re- set. Only issue with that though is the lower boss branch look glued so a fair bit of juggling to get it out and then replaced. Unless the bath waste could be routed somewhere else.

 

[Flibblewibble]

Photo? Can advise better if we can see the issue.

See attached. You can see the exit of the p trap in white pipe at the back… higher than the grey manifold so leaves it always partially filled with water.. Aware that the appliance waste pipe shouldn’t be coming up from below. Another professional did that.

 

[Hugh Jaleak]

Oh good god, its worse than I thought. You need get that sorted ASAP, it's fundamentally wrong on many levels, especially the washing machine/dishwasher drain hose, which in that configuration will allow dirty water discharged from the sink(s) to re enter the machine, contaminating whatever is already in there. In fact the backflow could well fill the appliance before it goes to drain!

I'd get rid of the lot, fit 2 P traps, (one with a spigot for the drain hose, which also needs looping up to the underside of the sink, so it falls to the drain point), then tee them in correctly to the outlet.

 

[Madrab]

Yes, couldn't agree more, that waste system is a nightmare, it's a European bespoke double sink waste setup that would usually be supplied by the sink manufacturers - IKEA/Franke etc. and it really needs to go. The big issue with all that, apart from the crap quality waste, is they've tried to hide the outflow and pipework behind that panel. An admiral thought if they had done it properly.

If you don't want to alter the white outflow pipe and that back panel then can't do better than following @Hugh Jaleak 's approach.

The other thing is I don't know why kitchen fitters seem to think it's ok to fit a double socket in a place that probably has the highest risk of getting wet, under a sink. Oh and no obvious ISO's on the H&C pipework.

 

[Deluks]

I had one of those grey manifold things on a previous sink. Not the end of the world, you'll just have to lower the horizontal bit on the outflow to below the manifold, as you've noted. It just means cutting or drilling the back panel to fit it in.

Could the WM outlet be fixed to the top blanking plug instead?

I had a recent one where builder had put sockets low down behind washing machine, spark came in, tutted and replaced them with IP66 outdoor sockets fitted higher up.
You might want to do the same with that socket.

 

[Flibblewibble]

Thanks all,
On the sink, I have done a quick “fix” of moving the WM waste so it comes in from above. Couldn’t be without WM any longer. Think it is ok for now but not ideal with the manifold swimming in water.
There are isolators on the hot and cold behind the panel.
Main headache remains the initial post about the WC waste stack and bath…

 

[Hugh Jaleak]

Washing machine connection is infinitely better and will suffice until a more permanent solution can be found.


Stack, there's 2 possible solutions I think. First, (not so ideal) is to reroute the waste (room permitting) on the same plane, and use one of the other Boss sockets, at 90º to the WC connection, 45º and 90º bends needed, provided it doesn't compromise the fall on the waste from the bath. Make sure run is able to be accessed for cleaning should it gunge up on the bends.

If sufficient fall is not available, how accessible is the stack lower down to tap in at a suitable point, to clear the required 200mm from the centre of WC Branch? If this isn't going to work, then last option, cut stack lower down, remove solvent welded short Boss Pipe and junction, replace with Manifold and new branch.

Either way, cap existing entry, (and ensure cap cannot be displaced.) Ridiculous amount of faffing about simply because original installer was either ignorant of, or couldn't be bothered to, install to comply with the regs, and this is the result....

 

[Flibblewibble]

Thanks Hugh,

As you rightly observe it's now all a massive amount of faff because of the original installer... sad state of affairs with no comeuppance for the cowboys.

On your suggestions:
- It's quite tight to get into the 90 degree bosses as the boxing in is only around 180 mm off the wall.
- The stack below the floor actually immediately bends back towards the bath connection (2x 45s I think), one of which has a boss for the shower connection to come in at right angles. This might be most viable if it's possible to drop into the side boss of one of the 45s.

On the building regs (hate these documents which are written with ambiguity):
Assume you have been referring to:
1.10 A branch pipe should not discharge into a stack in a way which could cause crossflow into any other branch pipe. (See Diagram 2.)
Diagram 2 then says "Opposed connections large than 65mm (without swept entries) should be offset at least 200mm irrespective of stack diameter."

Feels like this implies that opposed connections with swept entries don't require the offset. The WC connection is swept I think? But the bath connection definitely is not. Is that a get out for the "plumber" as we are probably going back to them with this.

Thanks again.