Bathroom waste

[Jim_cam]

Hi everyone - I'm redoing my bathroom and I'd be very grateful if you could let me know if I'm on the right track with the waste pipes. It was very manky before so I removed all the units and I've got the floor up now so this is a perfect chance to make sure it all works well.

Originally there were two basins and a shower feeding into one 40mm pipe (no drop!) which runs into the soil stack. I've plumbed out one basin and I want to add a bath. It's not feasible to give the outlet from the bath its own run -- it will have to join the same waste pipe as the shower and remaining basin.

From reading lots of threads here it seems like I'll need an anti-vac trap under the basin, and maybe an air valve by the shower trap (i can run a pipe from there up behind the false wall if necessary, as i understand it needs to be accessible and a certain height). A quick sketch of the plan is below. Does this look about right? Is there anything else I need to bear in mind to avoid smells / slow draining / water coming up through the drains?

---- thanks in advance for any help, this forum is a lifesaver.

 

[Hugh Jaleak]

Sounds like you've done your homework, the AAV needs to be above the spillover level of the basin, and accessible for maintenance. There needs to be some fall on the waste, if its dead level you are just asking for trouble.

In the ideal world the shower would have its own waste, but if it cant be done, fit a HepVo or non return valve on the shower waste before it commons with the other appliances. Went to look at a job a while back, young couple had bought their first house. Found bath, shower and basin on same 40mm run. The Lass had let her bathwater go, she went into the bedroom, came back out to find the bathwater had erupted from the shower, and flooded the bathroom and kitchen below.

 

[Jim_cam]

Haha that's exactly what I'd like to avoid!! The shower came with its own little bottle style waste but nothing that would stop water coming back through. Various people have suggested that hepvo and non-return valves are prone to blocking (particularly if your girlfriend has long hair and loves taking showers); when the floor is tiled they'll be difficult to access if they need fixing. Is there any alternative?

Also - I was looking through the Mcalpine catalogue and its sample plan showed the AAV not by the shower but branching off right at the sink, which was first in the run (like mine). I'd assumed that to help with shower drainage it would need to be next to the shower trap, but i could have it earlier instead if that's preferable. Any thoughts?

Thanks for your help Hugh - I've found reading your contributions to other threads really useful

 

[Hugh Jaleak]

AAV ideally needs to be at the head of the run, but looking at your diagram, there may be an issue with the bath pulling the shower trap, especially once the waste gets gunged up a bit. Although I'd hope the antivac basin trap would suffice, it may be better to fit an AAV on the shower waste now, rather than retrofit something later,

HepVo or non return valves, basically both act as a NRV, Hep valve can be used instead of a trap. Nothing else will act as an NRV I'm afraid, if you're happy to keep an eye on things and give the waste a good, (mechanical, not chemical), clean every so often when it starts glugging, you may get away without a NRV.

Ditch the waste you have, and look at the shower traps with a removeable section to allow easy access to clean the waste if you are going to bury it all under the floor.

 

[Jim_cam]

Ok, cheers. If i use a hep valve instead of the waste ive got, can it be cleaned from above in the event of blockage?

 

[Hugh Jaleak]

No. You'll need to remove it I suspect and wash it out. To be honest though, looking at the design, if it did block, a good dose of pressure from a plunger should be enough to push anything blocking it through.

 

[Jim_cam]

Would something like this do the job?- https://www.wirquin.co.uk/wastes/slim-90mm-shower-waste.html -- it's anti-back siphoning and specifies it can be cleaned from above.

 

[Hugh Jaleak]

The type with the membrane seal is the same concept as the Hep valve, and maybe the best option for your setup. Not seen those before, interesting idea assuming they work! Would prevent backflow and eliminate the need for a NRV or Hep valve.

 

[Jim_cam]

Thanks so much for your help mate- that's what I'll go with. I'll be sure to post back here when thrte's water pouring through the kitchen ceiling

 

[Hugh Jaleak]

If you're burying it all under the floor, use solvent weld waste, and test it before putting the floor down!