Shower plumbing - air admittance valve?

[omegaman]

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

As Richard said earlier, if the basin waste has a seperate branch then it won't matter if the AAV is lower than the basin waste because in this case the spill over level is the shower tray.

 

[Richard C]

As Richard said earlier, if the basin waste has a seperate branch then it won't matter if the AAV is lower than the basin waste because in this case the spill over level is the shower tray.

Thanks, brain not thinking straight.

 

[sludd]

OK guys

The stack does indeed go out through the roof and has just the standard grill on top - no air admittance valve.

It looks like the shower waste enters the stack lower than the basin and WC, and therefore the waste and water from these 2 appliances will pass the entry point for the shower waste into the stack.

Perhaps this is where the risk of syphoning is thought to be a possibility, but is this likely?

I have no experience in installing plumbing systems (just DIY), so maybe the house builder had previous experience with the other houses of the same design.

I'm basically a bit concerned that the location of the trap hole in my new shower tray might not allow a direct tie into the existing waste pipes and I need to reconfigure things a bit. If this is the case I don't want to screw up beacuse of this valve from the shower trap

 

[Richard C]

Perhaps this is where the risk of syphoning is thought to be a possibility, but is this likely?

No, it’s perfectly normal.

I have no experience in installing plumbing systems (just DIY), so maybe the house builder had previous experience with the other houses of the same design.

No real way of knowing why it's been done, perhaps the plumber was also the bricky or ran the local burger van . I would still advise you blank off the vent & see what happens while still using the shower; if the trap doesn't siphon, you don't need the vent. There is a remote chance the stack could be blocked in the dry section I suppose but a give away would be evidence of the vent being fitted as an add-on.

I'm basically a bit concerned that the location of the trap hole in my new shower tray might not allow a direct tie into the existing waste pipes and I need to reconfigure things a bit. If this is the case I don't want to screw up beacuse of this valve from the shower trap

Plumbing, waste systems & even foul drains isn't rocket science as long as understand a few basic rules & follow the Building Regs./design guidelines, it’s why they are there. Just re-arrange the pipe work under the shower with new fittings, as required & as long as it still points downhill you’ll be fine. This is quiet a good little guide & may help your understanding;
http://www.hunterplastics.co.uk/download/29/Design Criteria.pdf

 

[sludd]

Thanks Richard - you've been a great help.

I'll blank of the valve for a week or so and see how it goes.

I've changed a few basins, WC's, showers & trays etc in my time with no problems so far, so I'm sure I'll be OK - it was really just this valve thing I wanted to be sure about before starting, having never come across one before.

 

[Richard C]

I'll blank of the valve for a week or so and see how it goes.

I'd be very interested to know what happens, please come back & let us know.