Air admittance valve on waste question

[racey1979]

Hi,

I am currently fitting a bathroom, my shower and bath are tee'd to the same waste pipe with a sweeping tee piece, and there no other way of doing it really without making more big holes in walls and joists. Siphoning didn't seem to be a big issue on my old bath and shower but I've fitted new 43mm waste and new traps and tested it yesterday. It doesn't pull all the water out of the trap but it gurgles a bit and the water level drops. I was thinking of fitting an inline Mcalpine VP3 air addmittance valve to reduce this, like the one in the link. The question I have is, does the air valve need to be at the top ? If so, it will foul on my floor boards, would it be okay to rotate it so it clears, so it would be pointing to the side ?

Any help much appreciated, many thanks

Andy

Inline air admittance valve

 

[Mr Chibs]

I was under the impression that it's meant to be the highest point on the the pipework, could be wrong, I bought one but in the end didn't use it.

 

[Mr Chibs]

Just had a look at the valve, yes VP3, and I think you could install lower down as long as it's upright. Not a scientific answer, but might be helpful, there's no instructions in the bag.

 

[Hugh Jaleak]

Firstly, an AAV needs to be upright, it relies on gravity to hold the valve shut, unless operating.

Secondly, shower and bath on same run is never a good idea, should waste become blocked, letting a bath full of water go, can result in it erupting back through the shower and flooding the room. You would also have the issue, even with an upright AAV, of water escaping from the valve, hence why it needs to be above spillover level of highest appliance, i.e. the Basin.

 

[racey1979]

Firstly, an AAV needs to be upright, it relies on gravity to hold the valve shut, unless operating.

Secondly, shower and bath on same run is never a good idea, should waste become blocked, letting a bath full of water go, can result in it erupting back through the shower and flooding the room. You would also have the issue, even with an upright AAV, of water escaping from the valve, hence why it needs to be above spillover level of highest appliance, i.e. the Basin.

Thanks for this, as mentioned it's going to be difficult to do it any differently. I fitted the AAV yesterday (I soon realised they need to be upright so found a way of doing this) and then tested draining the bath water, I got no gurgling/siphoning and the shower trap maintained a water seal. However, it does put some water into the shower tray initially so I'm not happy so I'm going to attempt to reconfigure. My initial idea was to put the shower on it's own waste and remove the AAV, then tee the basin waste to the bath waste. But I'm really struggling for room under my floor boards to do this due to things fouling, so one option I'm considering is plumbing the basin out of the front wall of the house (pipes currently go through the side wall to their own seperate drain) and connecting to the square rain water pipe. This would mean the bath, shower and basin are all seperated. The house was built in 1953 and I'm fairly sure that its a combined foul and rainwater drainage system, no pipes are connected to the soil pipe for the toilet on any of the houses, and the kitchen sink waste is connected to the rain water drain pipe at the front that I mentioned. The issue now is connecting a round 32mm waste pipe to a 65mm square drain pipe, I can buy a square branch and guess I could just clamp the 32mm pipe to the wall so it just enters the pipe ? Or would there be a better way of connecting ? Or is this just a crap idea altogether lol ?

Thanks again, Andy

 

[Hugh Jaleak]

Waste pipes into rainwater downpipes are not the best of ideas, as the waste water can soon make gullies and Hoppers stink in warm weather, hence why the practice of putting bathroom wastes bathroom wastes into Hoppers were banned some years ago.

However, if kitchen already goes to this gully, then you'd be fine to connect a bathroom basin to it as well. Connecting however, is a different matter, there isn't a fitting available to my knowledge to connect waste pipe to rainwater, so some sort of improvisation would be needed.
Your idea of using a branch would probably be ok, but personally would look to trying to seal the joint somehow.

A preferable solution may be to upsize to 40mm externally, and drop to the gully in a separate run. Use an anti vac trap on the basin to prevent any siphonage there.

 

[racey1979]

Waste pipes into rainwater downpipes are not the best of ideas, as the waste water can soon make gullies and Hoppers stink in warm weather, hence why the practice of putting bathroom wastes bathroom wastes into Hoppers were banned some years ago.

However, if kitchen already goes to this gully, then you'd be fine to connect a bathroom basin to it as well. Connecting however, is a different matter, there isn't a fitting available to my knowledge to connect waste pipe to rainwater, so some sort of improvisation would be needed.
Your idea of using a branch would probably be ok, but personally would look to trying to seal the joint somehow.

A preferable solution may be to upsize to 40mm externally, and drop to the gully in a separate run. Use an anti vac trap on the basin to prevent any siphonage there.

Thanks you've been a great help. My plan was to make a nylon bung for the square branch, I'm a mech engineer and have access to millers, lathes etc so was going to machine a bung to fit, with a 32mm hole for the waste pipe, then silicone it in. The other option I have other than this is to tee the basin waste to the shower waste, as I can actually access this. The basin trap I have is an anti-siphon one, so would this be a better option ? With a lower volume of water than the bath waste, and the anti siphon trap do you think this would be okay, and not effect the shower waste too much ? Thanks again.

 

[Hugh Jaleak]

Basin into shower is not so much of an issue, done the same myself. Volume of water from the basin discharge will not cause an overflow in the shower, unless tap is left running, so unlikely to cause an issue down the line. May get some gurgling from the shower, (I've got my basin connected to the shower waste, and it can cause shower to gurgle if I let a full basin go, anti vac trap should help with that.) Would be better than connecting to the rainwater, assuming wastes go to the stack.

Have seen what happens when a bath and shower are connected to the same run. Friend of mine's Niece, her first home, called her Aunty in tears as she'd had a bath, pulled the plug, and gone into her Bedroom to dress. By the time she realised something was amiss, the water had spread across the Landing, and was coming through the kitchen light below the bathroom.

Long waste run taking shower and bath at the top end, had blocked, water had found it's own level and erupted through shower waste, quickly filling tray and overflowing onto the floor. That's why I'd never put a bath and shower on the same run.