Air Admittance Valve

macbog

Hi guys . Can anybody advise on the benfits or otherwise of fitting an Air Admittance Valve to the top of my soil stack vent in the attic ? Does it meet regulations ?

seensensee

macbog wrote: »

Hi guys . Can anybody advise on the benfits or otherwise of fitting an Air Admittance Valve to the top of my soil stack vent in the attic ? Does it meet regulations ?

Why do you think you need to fit one?

macbog

seensensee wrote: »

Why do you think you need to fit one?

Its a 2.5 inch vent going through the roof , but I dont think its big enough . Was going to fit a 4" vent with an aav . The reason been have a smell coming up the toilet like sewer gas .

seensensee

macbog wrote: »

Its a 2.5 inch vent going through the roof , but I dont think its big enough . Was going to fit a 4" vent with an aav . The reason been have a smell coming up the toilet like sewer gas .

So the 4"soil pipe tee's up and has been reduced to 2.5'' which passes through your roof and vents out to the open air?

when you flush, any vacuum is nullified by the vent pipes ability to suck in air. Any gases which emanate from the sewer travel through the vent pipe and out. There is no apparent way for gases to leak back through the toilet.

Have you/can you check the fittings? it's possible that a connection has worked its way lose some where along the line... it's a more likely explanation for the smell, imo.

A few things to consider, has the smell been a recent event?
Does your toilet flush correctly such that the water level in the bowl is at the normal level?

EDIT: of course the 2.5'' may be blocked that needs to be checked.

seensensee

After giving it further consideration it seems obvious that an AAV certainly will not help your present situation.

macbog

seensensee wrote: »

So the 4"soil pipe tee's up and has been reduced to 2.5'' which passes through your roof and vents out to the open air?

when you flush, any vacuum is nullified by the vent pipes ability to suck in air. Any gases which emanate from the sewer travel through the vent pipe and out. There is no apparent way for gases to leak back through the toilet.

Have you/can you check the fittings? it's possible that a connection has worked its way lose some where along the line... it's a more likely explanation for the smell, imo.

A few things to consider, has the smell been a recent event?
Does your toilet flush correctly such that the water level in the bowl is at the normal level?

EDIT: of course the 2.5'' may be blocked that needs to be checked.

Best start at the beginning . About 2 year ago I fitted a WC and saniflow unit under the stairs . I connected the 3/4" outlet from the saniflow unit to the internal soil stack 6" above ground floor level . After 6 weeks I noticed a smell like wet carpet in the upstairs bathroom . I increased the vent pipe to 4 inch for 2 feet above the joint of the upstairs loo . The smell went for 6 weeks . When the smell came back I took the 4" vent pipe up to ceiling height and the smell went away for 7 months but now its back again . I thought if I took the 4" through the roof it might solve the problem but because the pipe exits close to the wall of the house next door thats not possible . Thats why I was looking at an aav . Checked the joints and there ok . The smell appears to come from the water in the toilet . Sorry fo being so long winded

seensensee

The thing is that an AAV works by admitting air due to the vacuum created as a toilet is discharged through the stack, it enables a siphon free flush that's all. It certainly will not remove a sewer gas smell from your system.

Any diameter of vent to air is better than a sealed (AAV) system for removing gases. If you are going to work on the soil stack then a couple of 15 degree offset bends will help you clear the wall.

Good Luck.

Carlow52

Seems to me that the issue maybe the pressure being created in the stack by the sanlflow if the piping was not done correctly. have u a picture?

Some questions on your post:

Best start at the beginning . About 2 year ago I fitted a WC and saniflow unit under the stairs . I connected the 3/4" outlet from the saniflow unit to the internal soil stack 6" above ground floor level .

Describe the stack setup at that time above the connection, including where/how it vented?

After 6 weeks I noticed a smell like wet carpet in the upstairs bathroom . I increased the vent pipe to 4 inch for 2 feet above the joint of the upstairs loo

.
Describe the stack setup at that time above the connection, including where/how it vented?

The smell went for 6 weeks . When the smell came back I took the 4" vent pipe up to ceiling height and the smell went away for 7 months but now its back again .

ceiling height where? and again how is it finished off vented?

I thought if I took the 4" through the roof it might solve the problem but because the pipe exits close to the wall of the house next door thats not possible

.

what pipe exits where?

Thats why I was looking at an aav . Checked the joints and there ok . The smell appears to come from the water in the toilet

Pressure build up in pipe maybe: how did u connect the 3/4 pipe: just drill a hole through the stack and a bit of silicone or what?

Can u check any external AJ's to look at flow?

Joey the lips

I will read this again later as i am slightly confused but from what i read you dont need an aav. A 2" pipe venting 4" is perfect and in line with building reguilations.

The smell your getting. Its very unusual. Have you been cleaning out the sani flow unit.

Have you a shower in the bathroom. Is there a chance that the shower trap needs cleaning.

btw. you can also fit a 2" aav on top of the 2" pipe if your worried about the smell from that.

Low Energy Eng

Joey the lips wrote: »

I will read this again later as i am slightly confused but from what i read you dont need an aav. A 2" pipe venting 4" is perfect and in line with building reguilations.

The smell your getting. Its very unusual. Have you been cleaning out the sani flow unit.

Have you a shower in the bathroom. Is there a chance that the shower trap needs cleaning.

btw. you can also fit a 2" aav on top of the 2" pipe if your worried about the smell from that.

Joey,

I think the regs call for a minimum of 80mm min vent pipe, but in reality I'd imagine a 2" being fine

OP if you could upload a pic of the setup it might be a bit clearer

I cant understand why you'd fit a AAV if its being vented to outside though. You have a leak somewhere because the vent is not to get rid of smells as such, its to prevent syphonage

Those saniflow units are quite troublesome, have a very good look at that first

Micky Dolenz

I think the regs actually allow a minimum diameter of 32mm for a vent as long as it is only servicing a certain amount.

macbog

seensensee wrote: »

The thing is that an AAV works by admitting air due to the vacuum created as a toilet is discharged through the stack, it enables a siphon free flush that's all. It certainly will not remove a sewer gas smell from your system.

Any diameter of vent to air is better than a sealed (AAV) system for removing gases. If you are going to work on the soil stack then a couple of 15 degree offset bends will help you clear the wall.

Good Luck.

Thanks for your help seensensee . I will go with the 4" vent pipe through the roof .

macbog

Carlow52 wrote: »

Seems to me that the issue maybe the pressure being created in the stack by the sanlflow if the piping was not done correctly. have u a picture?

Some questions on your post:


Describe the stack setup at that time above the connection, including where/how it vented?

.
Describe the stack setup at that time above the connection, including where/how it vented?



ceiling height where? and again how is it finished off vented?

.

what pipe exits where?



Pressure build up in pipe maybe: how did u connect the 3/4 pipe: just drill a hole through the stack and a bit of silicone or what?

Can u check any external AJ's to look at flow?

Sorry about the confusion guys . Originally I had a 2.5" pipe venting the soil stack . Because of the smell in the bathroom I increased the size of the vent pipe to 4" up to celing hight reducing to 2.5" for the remaining 4' going through attic and roof . Thanks . Macbog

Micky Dolenz

Did that work?

I would be surprised if it did, unless the pipework that was replaced was faulty.

macbog

Micky Dolenz wrote: »

Did that work?

I would be surprised if it did, unless the pipework that was replaced was faulty.

No it didn't . The smell is back .

Micky Dolenz

The smell has nothing to do with the stack being ventilated. Your current set up sounds good.

If there is water in the toilet bowl it is nearly impossible for smells to be coming back through the full trap.

My money is on the connection between the toilet and the soil stack. It's a white fitting with a black rubber that seals at the toilet bowl, it is common for them to be unsettled through movement and lose their seal. May be worth replacing.

macbog

Micky Dolenz wrote: »

The smell has nothing to do with the stack being ventilated. Your current set up sounds good.

If there is water in the toilet bowl it is nearly impossible for smells to be coming back through the full trap.

My money is on the connection between the toilet and the soil stack. It's a white fitting with a black rubber that seals at the toilet bowl, it is common for them to be unsettled through movement and lose their seal. May be worth replacing.

Thanks Micky I will do that . Guess it's just a process of elimination ?