Traps / drainage / smells. please help

Yes, shouldn't be any smoke from anywhere other than the open vent end of the stack. Drains and stack should ideally be air (and smoke!) tight, but especially any pipework above ground or in/under the buildings.

Rats will chew through concrete if they need to, the resin liner will present no challenge to them!

Thanks - the smoke test wasn't really conclusive either way.

First of all, the smoke was placed at the bottom of the stack (using an inspection panel) and the pipe below it was bunged. No smoke appeared or could be smelled anywhere in the property - however, I couldn't see it coming out of the stack either - but the smoke was a light grey type and it was a bit windy - who knows.

when the smoke test was done first time round, by someone else, and I could smell it in the downstaris WC, it was placed in the manhole - ten feet away from the stack - in the start of the foul drain. To my mind, it should have been done here again so I could compare like for like. having said that, it may be that I could smell it in the WC precisely because of the hole in the sub-floor that the rats were using, rather than the pipe. god knows - it's all too bloody difficult!

one thing that was noticed - when the stack was bunged and the WC sink filled up and then left to drain, it sucked the air out the trap for the washing machine. we then put an air admittance valve on the washing machine trap to stop this happening.

I've noticed that in my upstairs bathroom, the bath draining out also always sucks the air out the trap of my sink upstairs (I'm assuming the loud gurgling is the air sucking out??).

This isn't normal is it? Do I need to get all my traps checked for this?

one thing i don't follow - even if the air is sucked out does it really matter given the sink / washing machine is in constant use - wouldn't that mean the trap is always being refilled? surely it only matters in a sink or appliance that you never use - so the trap is never re-filled and then starts smelling.

The only way a trap is always refilled is to have a tap constantly dribbling.So yes it does matter

ok, thanks I'm going to get all the traps checked for induced siphonage.

EDIT - I couldn't get a reliable plumber to show up before the dry weather ended.. and now it's been raining on and off, the smell has disappeared.

If anyone can offer an explanation as to why rain water has such a direct effect please, please let me know! I just cannot understand how it works, and no plumber has offered any explanation.

It must be that I have an ineffective trap which is open periodically all year round but only smells when the sewers are dry with no rain sloshing through them?? possible?

or I have a trap somewhere in the building that only gets filled when it rains?? is there such a thing?


I'm happy to offer a reward in thanks! the problem won't arise again now until next summer..

Tom10001 said:

EDIT -

It must be that I have an ineffective trap which is open periodically all year round but only smells when the sewers are dry with no rain sloshing through them?? possible?




I'm happy to offer a reward in thanks! the problem won't arise again now until next summer..

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In London a lot if not all of the sewers are combined foul/rainwater

My rain water and foul are combined - I only have one main pipe into the sewer mains.

But what's the effect of that? I mean how does knowing that help me in terms of a solution ?

Simple, in times of heavy rainfall, the sewers get a good wash out. Years ago town sewers discharged onto a field near the watercourse downstream of the town, and relied on the extra flow during storms to flush the sewers through and wash all the accumulated sludge off the fields. Virtually all sewage treatment works have 'storm tanks', large tanks that collect the excess flow in times of heavy rainfall and retain it to be pumped back to the inlet to the works, when flows have reduced again, for treatment.

Chances are the rainfall has led to increased flows which in turn have washed the drains through, removing any collected detritus which is decomposing and giving rise to the smell you report. You've still got a trap being syphoned or broken pipework which is providing as escape route for foul air into the building.... Only the air is somewhat purer at the minute so less noticeable.

Understood. Thanks for explaining

So then it's still a case of locating the trap or problem pipe work - which everyone has been unable to do so far

Thanks again.

The rainwater pipes should each discharge into a trapped gulley to isolate them from the sewer- so look @ the bottom of the rwpipes.

Thanks Nige, I checked at the bottom of each r/w pipe, there are two coming off the roof at the back - both have gullies filled with water (they did before the recent rainfall too).

Tom10001 said:

T

when the smoke test was done first time round, by someone else, and I could smell it in the downstaris WC, it was placed in the manhole - ten feet away from the stack - in the start of the foul drain. To my mind, it should have been done here again so I could compare like for like.

.

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Had another thought ! Due in part to my re doing some drains@ home and laying a path. In the recent rain I heard an unusual noise in the foul manhole - looked in ( can't resist it) and saw groundwater spurting from a crack in the brickwork and dropping into the channel. - the crack is barely visible when all has dried out. Also I found several voids under the existing concrete that I broke up to lay a new path . I'm wondering if the smell is creeping through your manhole brickwork and through voids in the clay to your wall and then through other small cracks into the house - wet clay expands and the small voids are sealed !

Thanks Nige - appreciate your help.

The manhole is outside though and the only way in would be through the new extension which is solid walls and a concrete sub under tiles..

I've bought some smoke pellets to see if I can locate the problem trap (if that's what it is..).

EDIT - SOLVED

Just wanted to say thanks for everyone's help and offers of advice.

For anyone who's interested: In a fit of desperation I had the skirting boards off and lifted up the pristine engineered wood floor, insulation, floorboards etc.. to find that one of the brand new pipe that the builders laid down to connect to utilities, wasn't actually connected to anything and was completely open. Hence the rats and the awful smells that came only in the summer - (Hugh Jaleak explained why above).

Sounds completely obvious, but it wasn't easy to find despite 3 camera surveys , smoke tests and the rest. The red herring was the fact that the pipes all looked good and the utilities all worked well without leaks.

anyway, what a relief.

Nige F said:

Smells will travel up boxings/ducts through small holes in walls etc. Something I discovered in a large old hotel I worked at (found an open drain pipe in the basement)

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I forgot to mention the hotel was old but had been worked on/refurbished in the 1960's by London Builders not local Sussex tradesmen ( they had done work in the '40s.) So the London Boys are still forgetting what they do with pipes then