Plumbers - Air Admittance Valves?
Discussion
We fairly recently had a new bathroom fitted that consists of a bath, two sinks, walk in shower enclosure and a WC. There is no external stack and we are led to believe the system uses an AAV which is concealed in a small false wall, boarded and tiled in said bathroom.
Just recently the shower has started to back up and won't drain away (until the trap is removed). In addition to this the water in the WC rises abnormally when flushed, and the waste water from a filled sink or bath also struggles to drain away clearly, and as it does so the water in the shower trap gurgles and spits out all over the place like some dirty old w
e.
Now then, if you remove the shower trap therefore opening the shower drain to the atmosphere the WC and sinks/bath all drain away properly. This we have been told is possibly down to the air admittance valve going faulty. The chap who gave this advice suggested that it may be worth drilling some small holes into the boxed in pipe assembly to allow more air into where the valve is situated.
Am i wasting my time drilling? Does it indeed sound like a faulty AAV? Or is there anything else i can try before i have to remove tiles/chop into the false wall and generally make a fking mess of what is a lovely bathroom 
Many thanks,
R
Just recently the shower has started to back up and won't drain away (until the trap is removed). In addition to this the water in the WC rises abnormally when flushed, and the waste water from a filled sink or bath also struggles to drain away clearly, and as it does so the water in the shower trap gurgles and spits out all over the place like some dirty old w
e.Now then, if you remove the shower trap therefore opening the shower drain to the atmosphere the WC and sinks/bath all drain away properly. This we have been told is possibly down to the air admittance valve going faulty. The chap who gave this advice suggested that it may be worth drilling some small holes into the boxed in pipe assembly to allow more air into where the valve is situated.
Am i wasting my time drilling? Does it indeed sound like a faulty AAV? Or is there anything else i can try before i have to remove tiles/chop into the false wall and generally make a f
king mess of what is a lovely bathroom Many thanks,
R
Busamav said:
Casings to dergo valves nowadays are required to have ventilation and adequate access for maintenance.
Bit late for that!! 
The boxing in is not airtight, as where the 4" WC waste pipe exits the loo and joins the existing stack the cut out through the boxing does have approx an inch gap around it so air can get in there, but is that enough?! As it's something that just started happening i can only assume the AAV has packed up working... (Why would it have worked ok for a while then stopped working properly?!)
No. I would say it was the drain blocking.
AAVs admit air, so they remain closed when flushed.
Incidentally the requirement for soil systems to have no moving parts is waived under the BBA Certificate for AAVs. BUT one of the conditions from the BBA for this is that they are readily accessible for servicing.
That AAV has been fitted by a moron.
AAVs admit air, so they remain closed when flushed.
Incidentally the requirement for soil systems to have no moving parts is waived under the BBA Certificate for AAVs. BUT one of the conditions from the BBA for this is that they are readily accessible for servicing.
That AAV has been fitted by a moron.
Baldy881 said:
Busamav said:
Casings to dergo valves nowadays are required to have ventilation and adequate access for maintenance.
Bit late for that!! I was just stating what is required now .
Maybe you could design in access to the boxing out where you could then remove the valve and rod the stack for the future .
If you can cut a neat enough hole where the AAV is you could make good with one of these.
http://www.screwfix.com/app/sfd/cat/products.jsp?i...
I personally always try to run them up into the loft.
http://www.screwfix.com/app/sfd/cat/products.jsp?i...
I personally always try to run them up into the loft.
Ferg said:
No. I would say it was the drain blocking.
Hmmm, if it is the drain blocking (bearing in mind that the bathroom has only been in use for approx 3 months from new and everything worked fine until about 2 weeks ago when the shower just started backing up), then why does the water all drain away ok from the sinks/bath and bog when the trap is removed from the shower? Surely if the drain was blocking then when i run the taps on the sink and bath with the shower trap removed it would also drain away slowly, which is not the case? Even with the shower trap in situ and full of water, full pelt running tap water does drain away ok, it's only when you plug the sinks and let them get say half full and then drain that the drainage is slow and the shower trap spits and gurgles.
So, the other thing i read yesterday when looking into AAV's is that they should be fitted above the highest 'flood' point of any attached part, in our case this is obviously the two sinks. So am i right in thinking that the AAV should be above the height of the top of the sinks basins? If this is important then this isn't the case in our installation.
Before i start doctoring this boxing and hacking the tiles up (which when reinstalled will have an access hatch!) i just want to get as many facts as i can, may be that i go back to my builder and get them to sort it if he will, however if it just a faulty AAV then i'm prepared to fix myself.
So the question that still seems unanswered is this, if it is blocked drains rather than a faulty AAV, then in peoples opinions should it make any difference whether the shower trap is in place or not?? As all the problems seem centred around that trap, if it's in place any volume of water discharged causes it to gurgle and spit water out, if it's taken out then any volume of water discharged seems to drain away ok. So, can the effect of a blocked drain be solved by temporarily removing a trap?
Is it worth removing one of the sinks traps so that one of the sinks wastes is open to atmos then trying the shower (with trap in situ) to see if it drains ok and would this actually tell me anything?!
Cheers,
R.
Sounds like the whole plumbing install is pony.
What do you mean by 'removing the shower trap'? The whole trap - which is under the shower tray or the trap cover?
What order are the fittings in along the branch?
What size pipes did they use? How far away from the stack is it?
Who did the install? What did Building Control say about the plumbing install?
What do you mean by 'removing the shower trap'? The whole trap - which is under the shower tray or the trap cover?
What order are the fittings in along the branch?
What size pipes did they use? How far away from the stack is it?
Who did the install? What did Building Control say about the plumbing install?
I agree with mycroft - get a Hepworth HepVo trap and install it in one of the basins - it will serve as an inline AAV and at least allow you to determine if there is an issue with the AAV in the boxing. Your symptoms don't sound like an AAV issue, but the way you remedy it certainly suggests the pipes are not blocked either.
mk1fan said:
Sounds like the whole plumbing install is pony.
What do you mean by 'removing the shower trap'? The whole trap - which is under the shower tray or the trap cover?
What order are the fittings in along the branch?
What size pipes did they use? How far away from the stack is it?
Who did the install? What did Building Control say about the plumbing install?
The trap we have is just like this one...What do you mean by 'removing the shower trap'? The whole trap - which is under the shower tray or the trap cover?
What order are the fittings in along the branch?
What size pipes did they use? How far away from the stack is it?
Who did the install? What did Building Control say about the plumbing install?
So when i say remove it what i mean is remove the chrome cap, then pull out the insert and finally the cup that sits into the trap housing (bear in mind i'm no plumber so can't do plumber speak). That just leaves the bit of the trap that is fixed into the shower tray (ie non removable), but in effect all it means is that the waste pipe that goes from the trap assembly to the stack is open to atmosphere. It would be the same effect removing all the water from the trap which would also open the shower waste to atmos therefore letting in air.
I was messing with it again last night and it just looks as if there is an air lock in the shower bit, to the point where you'd think it's the shower waste that is blocked as with the trap correctly installed the water from the shower just does not run off at all from the shower, but if that was the case then it wouldn't affect the basins/bath and loo? Once the trap assembly in the shower has been dismantled to allow air into the shower waste all the other bits work properly and the shower water drains away normally too.
The point is all this did work fine, but then just started backing up two weeks ago which certainly points to component failure! Sounds like the valve on the sink suggestion is going to be worth a go to either condemn or rule out the existing AAV.
As far as i'm aware all pipe sizes are normal and correct. The shower enclosure is pretty much right next to the stack, the run from shower trap to stack no more than 4 foot, loo to stack 2 foot, sinks and bath no more than 5 foot. There are no what i would call long runs from each component to the stack.
R.
Above is what i would call a top entry trap , i fit them cos access to under the shower tray is often difficult . I wouldn't worry about AAV being below the highest appliance , its one of those things i have never been able to get my head round . Another thing you could try is to close off all possible vents , plugs in , overflows bunged up with a cloth and shower trap plugged , then give the WC a long flush . If the AAV is just stuck shut it may be enough to pop it open again .
Interestingly just called in at local plumb centre and nice chap there showed me an AAV, not much to go wrong with them is there?! Also interesting was that i noted the packaging stated that it DID NOT have to be fitted above flood height of the highest appliance... At least i'm feeling more confident that the work that has been done isn't a bodge, ok, the unit is boxed in but aside from that! Unfortunately said nice chap didn't seem to have any miracle ideas either.
Baldy881 said:
Not something i can get to and check, but again i would ask if this was the case then why would it work for 3 months and then suddenly develop the described fault?? Surely any pipework problem would have casued the issue from day 1?
Hair and soapscum can form quite an impressive barrier - if the slope is very slight, as it will be, it won't take much to slow the flow to the point where it can't get down the pipe fast enough.Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff