Shower plumbing - air admittance valve?

[sludd]

My shower in the en suite has what looks like an air admittance valve connected into one of the wardrobes behind the shower cubicle.

I haven't opened up the space below the shower base yet and don't know if it's in line with the shower waste, or connected via a t-piece etc..

Is this likely to be an air admittance valve?

If so, what is it's job and what should I be careful of when fitting a new shower base, trap etc...

 

[omegaman]

An air admittance valve is connected to the top of a stub/stack pipe. Its job is to let air in and is usually used if the stack can't be vented or if its a stub stack. I don't understand why it would be connected to a wardrobe? Can you take a picture of it?

 

[Nige F]

The Lion, the witch and the aav

 

[Richard C]

An air admittance valve is connected to the top of a stub/stack pipe.

Not necessarily

Can you take a picture of it?

That would help.

 

[omegaman]

An air admittance valve is connected to the top of a stub/stack pipe.

Not necessarily

I'm sure you're right. Out of interest, where else or how would one be used?

 

[Richard C]

An air admittance valve is connected to the top of a stub/stack pipe.

Not necessarily

I'm sure you're right. Out of interest, where else or how would one be used?

On an unvented branch that feeds the stack but exceeds design length for risk of siphoning; but they are smaller
http://www.screwfix.com/prods/42968...-FloPlast Air Admittance Valve 32 x 40 x 50mm
another method is to use a HEPVO waste; more elegant but achieves the same thing

 

[sludd]

I'll take a photo tomorrow and upload it (if I can work out how to do it).

The wardrobe reference is just the place where the AAV, if it is one, is located.

The shower cubicle is in the en-suite, but the wardrobe backs onto the shower cubicle (opposite side of the stud).

The 40mm pipework comes through the wall from under the shower base, at skirting board height and has a vertical run (upwards) of about a foot or so, with this AAV then in the top.

 

[omegaman]

I see. Thanks.

Basically ventilating the branch. You can also use anti-vac traps if the runs are too long.

Edit: Missed the HepVO bit.

 

[Richard C]

The shower cubicle is in the en-suite, but the wardrobe backs onto the shower cubicle (opposite side of the stud).

The 40mm pipework comes through the wall from under the shower base, at skirting board height and has a vertical run (upwards) of about a foot or so, with this AAV then in the top.

If it’s a small one, sounds like it may be fitted to the shower waste, presumably you have a w/c & washbasin? Can you explain/sketch/photo the rough locations of these relevant to the soil stack & relevant dimensions? Do you know how/where the shower/sink wastes connect to the system, i.e. into the vertical stack or the horizontal w/c branch?

If you can give accurate information, there may be a way of eliminating it completely.

 

[Richard C]

I see. Thanks.
Basically ventilating the branch. You can also use anti-vac traps if the runs are too long.
Edit: Missed the HepVO bit.

Your welcome

 

[sludd]

I've attached some photos of both the shower waste under the shower tray itself, where you can just about see the branch from a t-piece going through the stud partition - the first photo shows what is inside the wardrobe, though the picture is 90 degrees in the wrong direction.

In terms of other appliances, there is a basin and a WC, which both connect straight into the stack. The basin is about a 2ft run and the WC about 5ft, and both connect into the stack above floor level.

As far as the shower waste goes, the last photo shows the 40mm waste pipe going into the floor, where it presumably runs to the same stack, which is about 8 ft away, but the run must be within the height of the floor joists.

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• sludd
• 10 Feb 2010
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• sludd
• 10 Feb 2010
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• sludd
• 10 Feb 2010
• 1

 

[Richard C]

It’s as I suspected, a small AAAV intended to vent the shower waste run; I am, however, a little surprised you need it . You have separate runs into the stack for each appliance, as it should be, & the lengths of the runs are well within design criteria for unvented braches! Is the vertical stack internal or external? Is it actually vented, either by an external open vent or another AAAV? Does the stack appear in good condition?

Presumably, one was/is necessary or someone wouldn’t have gone to all the trouble of fitting it in your wardrobe! Can you tell if it was fitted when the tray was installed or has someone bolted it on afterwards? Before you decommission the exiting tray, I would be inclined to remove the valve & temporarily block off the pipe off just to see what happens; based on the info you’ve given so far, I can see no immediate reason for it being there

 

[sludd]

Thanks again - it was definitely installed at the time the shower tray was fitted for the first time

The house is only 8 years old and everything about the installation is exactly as it was when the builder left.

The stack is internal and is boxed in with plasterboard. It goes immediately into the loft above the en-suite and is vented at the top (don't know off the top of my head whether it is an AAV or just a grill over the top of the stack - but the condition is good, as you'd expect for a relatively new house.

It's actually not a problem for me to leave it - if I can get rid of it then all the better, but I mainly don't want to create any problems with my new shower tray and basin/wc installation.

 

[Richard C]

The stack is internal and is boxed in with plasterboard. It goes immediately into the loft above the en-suite and is vented at the top (don't know off the top of my head whether it is an AAV or just a grill over the top of the stack - but the condition is good, as you'd expect for a relatively new house.

Is the stack visible on the outside of the roof? If not have a look in the loft to see if you can see a similar valve but much bigger on the top of it? If you do have an AAAV in the loft, I’ll have some more questions.

It's actually not a problem for me to leave it - if I can get rid of it then all the better, but I mainly don't want to create any problems with my new shower tray and basin/wc installation.

It won’t cause any problems with your new tray or basin; one thing you must watch is that the top of the AAV must always be above the highest point that water could ever back up in the event of a blockage, usually the rim of the wash basin is the highest flood line.

As I said, with separate connections & the length of pipe runs you have, I’m at a bit of a loss to understand why it’s there!

 

[sludd]

I'll check the top of the stack when I get home - this smaller valve in the wardrobe is definitely LOWER than the height of the basin though. The top of the valve inside the wardrobe is about 18 inches from floor level