Air Admittance Valve Advice in bathroom

[Kimber]

Hi,

Back again after the excellent advice last time! So when the BCO popped round last week, he mentioned about an AAV in the toilet. I said it shouldn't be needed, as I have a vent stack, but it has got me thinking. So a bit of advice please!

The toilet set up is exactly the same as previous, except for the manhole, but I was planning on attaching the sink waste to the toilet, with something like in the link;

Space Saving 90° Bend with 32mm Outlet

However, this sink arrangement would be a slightly different set up to previous, as the sink drain used to discharge into an bottle gully, that we will no longer be using.

Part of the reason for using this attachment, rather than a separate entry into the underground pipe work for the sink, is 1) space to get into the pipework (due to the bends) and 2) I'm not 100% sure on the final layout of the room.

However, the although the BCO seemed OK with my comment, I'm wondering if I am going to get siphoning of the sink trap, when the toilet flushes?

Should I fit a 32mm/40mm AAV between the sink and toilet? Or maybe an anti-siphon trap? Or are neaither going to help, and I actually am going to have to fit a 110mm AAV? Image below should show the current plumbing layout. Red is existing pipework, blue is the pipework I modified last week, and green shows the proposed sink location.

 

[JCplumb]

If you're connecting straight into the stack that is open to atmosphere then you shouldn't need an AAV if your pipes are properly sized.
If you're tapping into the run of soil between the stack and the loo then you'll need an AAV, you can choose either a trap with built in AAV or a standalone AAV, up to you.
I'd go with a McAlpine trap under the sink with built in AAV.

 

[Kimber]

If you're connecting straight into the stack that is open to atmosphere then you shouldn't need an AAV if your pipes are properly sized.
If you're tapping into the run of soil between the stack and the loo then you'll need an AAV, you can choose either a trap with built in AAV or a standalone AAV, up to you.
I'd go with a McAlpine trap under the sink with built in AAV.

Thanks for the quick reply. Just to be clear - toilet shouldn't need a AAV, but put one one of these on the sink;

https://www.NoLinkingToThis/p/mcalp...gclsrc=aw.ds&dclid=CPbyoZiajt4CFZch0wod8bAJSQ

 

[JCplumb]

Correct.

 

[chris watkins]

No need for anti-trap if discharge branch is sized & run correctly as per Part H.
Just for the record it is a basin in the toilet not a sink, they are in kitchens.
Personally I would have had the drain point coming out of the ground to the right of the WC pan with a small stub stack with an access cap just at overspill level. You could then clear any blockages without removing the pan or lifting the manhole cover and have a waste float running along the wall in 40mm from it to the 32mm basin waste, with not an AAAV in sight.
Still what do I know.

 

[Kimber]

No need for anti-trap if discharge branch is sized & run correctly as per Part H.
Just for the record it is a basin in the toilet not a sink, they are in kitchens.
Personally I would have had the drain point coming out of the ground to the right of the WC pan with a small stub stack with an access cap just at overspill level. You could then clear any blockages without removing the pan or lifting the manhole cover and have a waste float running along the wall in 40mm from it to the 32mm basin waste, with not an AAAV in sight.
Still what do I know.

Thanks for the reply. I have been reading Part H, and think I understand but I wanted to clarify with some professionals before pushing on.

Unfortunately we can’t employ people to do everything for us, as we’d quickly run out of money. You right about the I could have put the waste coming out next to the pan, but like I said, I’m not 100% on the finished layout yet, so can’t be sure left or right is right! I need to concentrate on the kitchen dinner first. Maybe I shouldn’t have started this, if it wasn’t fully planned, but we needed to do the floor right through this area, so we are where we are.

Don’t think you needed to sign off with your last line though. You clearly know more than me about this subject, which exactly W reason I am here asking the question. I’ve never ignored you’re advice previously, and was asking a worthwhile question.

Maybe it’s because I called a basin a sink?? Which must have confused everyone...

 

[JCplumb]

Maybe it’s because I called a basin a sink?? Which must have confused everyone...

That would be me, I'll be handing my quals back and turning myself in to the plumbing police once I've finished typing this.
If the building control officer said you need an AAV, I'd be putting it where I stated earlier, they're a quid or two more expensive than a trap without one so not a lot lost really and if someone was on here asking why the trap was losing its seal when they flush the loo with your pipe layout I and others on here would be suggesting an AAV.
The regs might not state that you have to have one there to be honest I don't know if they do or they don't, sometimes common sense trumps books.
I also once called a Belfast sink a farmhouse sink, I need shooting...

 

[chris watkins]

Sorry JC, I had a bad day my comments were over the top.
I don't want to compound it by having blood on my hands so please put the gun down.
however you will still need your quals to me in the post I'm afraid.

My poor excuse is that for a hundred years we never had a mechanical device fitted to a soil & waste system & the drains worked & the traps never pulled, so why do we need something that is prone to leaking or not working now?
It is a great shame that even BC Officers don't even seem to understand what is required by the Regs they are there to control.
OP it is a shame you can't get correct advice from your BCO which would save you the time on here but with respect just because you don't have the money & want to DIY it doesn't mean you not follow the same rules as a pro. The point about a basin being called a sink when it is not, is important as the rules for the maximum lengths of unventilated pipe are a lot different which of course you have seen i.e. 1.7m for 32mm as posed to 3m for 40mm.

 

[Kimber]

Sorry JC, I
OP it is a shame you can't get correct advice from your BCO which would save you the time on here but with respect just because you don't have the money & want to DIY it doesn't mean you not follow the same rules as a pro. The point about a basin being called a sink when it is not, is important as the rules for the maximum lengths of unventilated pipe are a lot different which of course you have seen i.e. 1.7m for 32mm as posed to 3m for 40mm.

Chris,

I do want to follow the same rules. When I'm doing my renovations, I am making sure that everything is being done by the book. Insulation, floor replacement, windows and everything. Being an engineer, I always do my research, check and double check. Appreciate the knowledge on the sink vs. basin though. I had clocked the difference between the 40 and 32mm piping, but didn't appreciate that calling them the wrong thing would cause that kind of confusion.

I guess as I don't know the full layout, it's a bit difficult for the BCO, as he won't be able to see the pipe length etc.

I realize what you are saying about the sub stack now. interestingly, I can probably still do this, as I thin there is the space to get the toilet and the basin on the back wall, with the stack between them. It's a layout I have been toying with, as long as I can disguise the stack. It's not something I really want to see in the finished room!

Thanks again.

Ian

 

[JCplumb]

I don't know if it's a regional thing but everyone I know except maybe the odd plumber calls a bathroom basin a sink, it's always been a sink to me and I have to stop and mentally correct myself to call it a basin.
Fair play to you Chris, some people would get their backs up at my sarcastic retort, you chose the grown up response
My quals are written on the back of a beer mat in crayon, where do I send them?

 

[Welder]

I
My quals are written on the back of a beer mat in crayon, where do I send them?

I hope your dad got you the beer mat? Under aged drinking is not to be encouraged in the impressionable yoof of today ...

 

[Welder]

I don't know if it's a regional thing but everyone I know except maybe the odd plumber calls a bathroom basin a sink, it's always been a sink to me and I have to stop and mentally correct myself to call it a basin.

Personally, 'anyone' can call it 'anything' so long as they pay me on time