Desperately need help with bathroom smell

Golden_Glow90

I bought a new house with DWH in 2014 with a 5 year builders warranty. Since April, there has been a sewage smell in one bathroom (the other bathroom and downstairs toilet are fine). This smell got worse even after using drain unblocker. A plumber was eventually sent out in June and found no stagnant water under the bath and no leaks or blockages. The smell had also appeared to have improved but I've now noticed that it is weather dependent; a few days without rain and the smell disappears, it rains and then the smell is back. I have told DWH this and they are refusing to send anyone else out to investigate the outside drains.

I don't want to call an independent plumber to investigate as I have no idea what the problem is exactly or which drain this particular bathroom runs to and so I'm worried about the costs that might be involved. Does anyone have any idea of what this smell might be, if it's something I can fix myself, how much it would cost for a plumber to fix or how to go about getting DWH to come and sort it out? I'm getting really desperate now. I have had no access to this bathroom in 3 months because the smell is sometimes so bad.

Grenage

It sounds like a breach in the soil stack, or toilet/sink waste - I can't think what else it would cause the odour.

Is the smell any stronger around any pipework?

Wookey

Soil stack vent to near an open bathroom window?

Are all rainwater gullies fully clear and showing no sign of backing up and are they discharging into the sewer? (can check that by lifting a sewer manhole cover and pouring a bucket of water mixed with a tiny amount of emulsion paint and pour it down the rainwater gullies and see if it runs thru the sewer manholes.

Washbasin overflow outlet, these can really stink at times from the buildup of soap/dirt and hair, give it a thorough cleaning with some bleach down thru it.

Golden_Glow90

Thanks for your advice. The smell doesn't appear to be coming from a particular area of the bathroom. I've tried sniffing around the bath, plug holes, sink and toilet. I've flushed drain unblocked and odour eliminator down the drains and the toilet twice so I don't think it's that.

If it was the soil stack vent then wouldn't the smell creep into other rooms too? We have our bedroom window open all the time at the moment which is next to the bathroom but no smell in the bedroom. How would I check this?

I'll try running water through the gullies, (isn't this the little drain in the ground under the gutter?).

rob7475

Could it be your sink or bath trap syphoning water when the toilet is flushed?

Next time you get the smell, try removing the traps from the sink and bath and see if there is water in them. If either are empty, that is where the smell is coming from. They would then need replacing with anti-syphon traps

Golden_Glow90

rob7475 wrote: »

Could it be your sink or bath trap syphoning water when the toilet is flushed?

Next time you get the smell, try removing the traps from the sink and bath and see if there is water in them. If either are empty, that is where the smell is coming from. They would then need replacing with anti-syphon traps

I don't think it's the traps. I tried plugging the plugs in and leaving some water in the bath and sink for a few days to see if this stopped the smell but it didn't. Even if the traps were empty, this should have stopped the smell coming through.

Plus, the plumber checked all the pipes in the bathroom itself which is why I think it must be something else causing the smell.

Wookey

The soil stack vent should terminate at least 1m away from the nearest window, most plumbers would try to offset it up around the roof so that it is vented above the level of the guttering. You do on occasion though see them finishing very close to a bathroom window, just look outside where the stack rises and you will see the 4" branch to the toilet in question and where it goes upwards after that, easily checked by keeping all windows closed all the time and see if the smell persists. As Rob says the traps could be syphoning out but this would be unlikely if there is a vent outside, if there is no vent then the chance of syphoning happening increases greatly and the bath trap is the most likely suspect as these are usually shallow seal.

Wookey

Golden_Glow90 wrote: »

I don't think it's the traps. I tried plugging the plugs in and leaving some water in the bath and sink for a few days to see if this stopped the smell but it didn't. Even if the traps were empty, this should have stopped the smell coming through.

Plus, the plumber checked all the pipes in the bathroom itself which is why I think it must be something else causing the smell.

If there is a bath waste/combined overflow the smell would come up thru the overflow part once the trap seal was lost.

Golden_Glow90

Wookey wrote: »

The soil stack vent should terminate at least 1m away from the nearest window, most plumbers would try to offset it up around the roof so that it is vented above the level of the guttering. You do on occasion though see them finishing very close to a bathroom window, just look outside where the stack rises and you will see the 4" branch to the toilet in question and where it goes upwards after that, easily checked by keeping all windows closed all the time and see if the smell persists. As Rob says the traps could be syphoning out but this would be unlikely if there is a vent outside, if there is no vent then the chance of syphoning happening increases greatly and the bath trap is the most likely suspect as these are usually shallow seal.

I can't see a vent. Only one pipe coming down from the gutter at the side of the house, not near the bathroom at all. I've looked at the other houses from the upstairs window and can't see any vent coming out of anyone else's roof either. Is this normal for a new build?

Golden_Glow90

If it was the bath trap, wouldn't the plumber have found this out when he investigated? Would the be written on the report? Should I ask DWH for a copy?

Apodemus

Golden_Glow90 wrote: »

I can't see a vent. Only one pipe coming down from the gutter at the side of the house, not near the bathroom at all. I've looked at the other houses from the upstairs window and can't see any vent coming out of anyone else's roof either. Is this normal for a new build?

Faulty Durgo valve? The valve is designed to open to prevent negative pressure in the soil pipe sucking out your sink and bath traps. It will be somewhere in the vicinity of the bathroom, but higher than the cistern. If it is stuck open, the smell will come out at the valve. If it is stuck shut, the sink trap will empty and the smell will come out that way. It replaces a soil stack on some new builds.