Smelly bathroom

[crt]

Hi, we've got nasty smells coming out of the wastes, principally shower, in our bathroom. We've used drain cleaner and flushed through but the smells remain.

The set up is WC waste into external stack; a couple of feet below, bath, washbasin and shower (in that orde) into the same stack. The stack is open to the air above not above roof height but a couple of feet above the WC waste). There is no evidence of an internal durgo valve (if they are internal).

Someone suggested a flap in the stack may have stuck or broken/perished. If so, where would this be?

Anyone have any suggestions?

Thanks.

 

[Richard C]

It sounds as if the traps are being "drawn". Do any of the traps share the same waste pipe run? All traps should have separate pipe runs into the stack or have an air inlet valve fitted to prevent the other traps being drawn. This happens, say, when the bath is emptied, the volume of water going through the pipe is enough to suck the water from the other traps, smells then find their way through the pipe from the stack.

If you have separate pipe runs, its possible the soil stack vent is blocked (birds nest!), air can’t get in & flushing the loo draws the other traps. You would only have a flap if a Durgo valve is fitted but if the stack is external it’s almost certainly open vented.

 

[crt]

Thanks.

The grey water wastes do all feed into the same near horizontal run into the waste stack. They do not appear to be independently vented, though each short vertical pipe into the horizontal run does have a screw cap on top.

How does the top of the vented stack come off?

CRT

 

[Richard C]

Thanks.
The grey water wastes do all feed into the same near horizontal run into the waste stack.

That’s probably the cause of your problem; bad practice & will give problems unless anti-siphon traps are fitted or each run has an air admittance valve.

They do not appear to be independently vented, though each short vertical pipe into the horizontal run does have a screw cap on top.

I can’t visualise how the vertical pipes connected to the shower/bath/sink can have a screw cap on the top! A picture or 2 might help!

How does the top of the vented stack come off?
CRT

It depends what’s fitted to it! Most just have a plastic mesh anti-bird cap that pulls off; are you sure it hasn’t got an air admittance valve fitted to the top?

Does the smell stop if you run a little water into the shower & sink traps? If it does, partially fill the bath & pull the plug, then check if there is still water in each of the other traps; you should be able to see it but if the smell returns, the traps are siphoning.

 

[crt]

Each grey water feed (1)-(4) comes out of the wall horizontally and then drops downwards about a foot into a common pipe (itself horizontal but perpendicular to pipes (1)-(4)) running into the side of the waste stack. Each of pipes (1)-(4) has a stub extending upwards which has a screw on cap.

Not sure how to post a picture.

 

[Blasphemous]

Our Bathroom and Down Stairs toilet always seem to have a smell after I've been in there.

On a more serious note.... A pic would be great to see what is going into what here. There is a thread or two somewhere on posting pics but I cannot be bothered to track them down at the minute.

As Richard says, it sounds like a bit of a DIY or bad practice plumbing job.... wasn't yours was it?

 

[crt]

Smelly soil pipe

• crt
• 7 Jun 2008
• 1

It turns out that inserting pics is now very easy because you can set up photobox type albums on this site. If it works, my set up should appear in this post.....

 

[Blasphemous]

Yep, I'd say its definitely 'pulling'. Flow from the 'other' wastes is pulling (siphoning) the water from your bathroom trap and probably the other traps. This will result in your trap (which is formed with water in the trap and is there to protect against smells coming back up the waste), failing to stop any smell from the soil coming back up the pipe and into the bathroom.

Running new pipework is one option although the window below probably rules that option out. The other option is to do as Richard says and fit anti-siphon traps or air admittance valves to each run.

 

[Richard C]

Smelly soil pipe

• crt
• 7 Jun 2008
• 1

It turns out that inserting pics is now very easy because you can set up photobox type albums on this site. If it works, my set up should appear in this post.....

Ohh, that’s not quiet what I was expecting; not ideal but that’s a fairly large diameter branch connection into the stack & those caps may well be air admittance (Durgo) valves but can’t really tell from the picture; if they aren’t they should be!

That soil stack terminates well below the window so it should have an air admittance valve fitted but that doesn’t look like one to me! If it hasn’t got one, it should have or it won’t comply with Building regs. Are you sure the smell is not coming from the top of the stack & finding it’s way into the bathroom? If it is a valve, it may well be that it’s jammed as your “someone” suggested!

I think you’re going to have to get the ladders out, get up there & have a good look!

 

[crt]

So.....this means putting an air admittance valve at the top of each vertical pipe which feeds into the horizontal run? (I don't want to have to replace all four traps). If so, do the valves need to be higher than the highest overflow level for each appliance or will they prevent water flowing over?

 

[Richard C]

Here’s a link to a useful guide which will do a far better job than I could trying to explain it all. From this, you should be able to decide the best way forward;

http://www.hunterplastics.co.uk/pdf/soilandwaste/swt3.pdf

I’m curious about how long ago that branch system was installed & if the “smell” is a new problem or has it always been like it? The branch also doesn't seem to have much of a "fall" into the stack but that could be a trick of the photo.

 

[crt]

It's been there about 8 years, and the smell has been present on and off for a year or so.

There isn't a great fall, but I think it is sufficient to allow water to run off. If the fall is too shallow can this increase the syphoning problem?

 

[Richard C]

It's been there about 8 years, and the smell has been present on and off for a year or so.

There isn't a great fall, but I think it is sufficient to allow water to run off. If the fall is too shallow can this increase the syphoning problem?

If it's only 8 years old, it probably didn’t comply when it was installed & it’s a bit iffy! The minimum falls depend on pipe size & flow rates & are also in the guide but 1:40 is usually about right. If the fall is too shallow, it won’t increase the risk of syphoning but water can lie in the pipe & it can be more prone to blocking; but it’s not generally a problem where just water & no “solids” are involved.

 

[blondini]

It looks like there is an air admittance valve on the top of the stack, I would bet it is faulty.

 

[Richard C]

It looks like there is an air admittance valve on the top of the stack, I would bet it is faulty.

Not really sure what it is; looks a little too flat but it could be; but even replacing it won't prevent the strong possibility of a bath or shower siphoning the other traps on that branch which is rather poorly done.