Can I solve bathroom gurgling before it happens?

greatgimpo

I'm fitting a new bath and shower upstairs in my bathroom. I already have an existing 40mm waste pipe coming vertically out from the floor maybe 75mm. I want to fit a tee and have the shower waste from one side and the bath waste from the other. Will I finish up with one or both gurgling, and can you suggest a better layout? Hepvo valves seem to be only mildly efficient and it's not going to be practical to have an air valve in the middle of the bathroom. Plumbing another waste in is also impractical.

Thank you guys, I bow to your superior knowledge.

unclebulgaria

You're not going to stop gurgling unless you install an air break.
Are you intending to ever use both shower and bath at the sametime because if you are you need to upgrade that 40mm pipe to 50mm.
The only other thing you could try is another water trap each side of the Tee which would look daft anyway.
Why cant you add another waste and just make it easier?

greatgimpo

To fit another waste in parallel would mean too much pain pulling up the chipboard floor. Incidentally, the pipework is all in one room so only one will be in use at a time, and the 40mm fittings will be hidden under the new bath.

unclebulgaria

The thing is, you're really supposed to go up a size if you have two equal sized pipes going into one common waste. How long is the waste from the Tee to the soil pipe?
I think you're going to have to get used to the gurgling unless you add an air break or another pipe.

greatgimpo

It's about 2 metres. Does an air break mean smells? Could I fit one in under the bath to the maximum height?

unclebulgaria

No there is a rubber valve assembly in an air break that stops smells.
You could I suppose but it'll have to be higher than any possible water emptying into the waste or it'll overflow. 2 metres is quite a long way if it has bends in it. Is there no way you could hide an air break in a false wall to the required height?

greatgimpo

Good point about the partition wall, I'll check the possibilities. I fancy fitting an air inlet up the inside of the bath, so guess it would be maybe 100mm higher than the bath when about to empty. Any good, or is that a gamble too much?

anotherbaldrick

An air inlet valve does not mean smells. Fit it on the vertical leg to the bath as high as you can reasonably below the underside of the bath rim. This will allow air to enter the system and not be pulled in through the trap seal which is your gurgle./

unclebulgaria

Can I just ask, how do you know its going to gurgle anyway? Is this a problem already?
You may not have enough height under the bath, it has to be above the flood level of the unit its supplying.

greatgimpo

No, I don't know it's going to gurgle, it's just that I'm fitting a new shower in and repositioning/replacing the bath to the existing waste underfloor, and want to avoid the problem rather than fix it afterwards.

unclebulgaria

sensible.
Have a look on the internet, there are lots of specs to heights and places to set them.