Traps / drainage / smells. please help

[Tom10001]

Hi, I’d be really grateful for any advice to help with this problem. I’m losing hope with it..


I live in a typical 3 bed terraced house in London. My house has its own drain, not shared with the neighbours. It runs under the house and leads to the main sewer pipe in the street.


Here’s the problem, when the weather is warm and only when it hasn’t rained for a week or more (only during height of summer), my kitchen and downstairs WC smell really bad – cabbage / eggs. This smell can go all the way up the house. It disappears very quickly if the windows are left open for 5 minutes. Then you don’t smell it again all day and evening, until the next morning when you come downstairs. So it’s very specific – only during prolonged dry weather and only first thing in the morning / overnight.


In terms of remedies, I’ve had 3 thorough camera inspections and smoke tests. They found one improperly capped, disused junction running off the main pipe. And they found several fractures in the main pipe running under the house. There was also a bucan / interceptor trap that was removed to prevent any future problems. The pipe was then sleeved to cover the disused junction and to deal with multiple fractures in the pipe. The soil vent was checked – no blockages or problems.


All sinks and toilets have been tested for leaks using a bung in the main pipe and filling them up with water. No leaks detected.


2 weeks later, I’m still getting the foul smells.


Possible answers:


– cracked pipes leaking foul water into soil under house which is then drawn up when the weather’s hot? - ok, but new sleeve in pipe should have solved this by now.

-Dishwasher or washing machine sucking or blowing air out of traps on end of cycle? – ok but the smell comes whether appliances are used or not.

-Empty traps due to dry weather? – ok, but in that case the smell would be constant and not just first thing in the morning wouldn’t’ it?.


As you can see, I’ve thought about this and spent a small fortune on having people look at it and repair things and still nothing doing. Am I missing something?? Any ideas?

I have no idea what else to look for. Could it be a loose seal in the downstairs WC? If so, wouldn’t it have leaked when we tested it?

thanks for your help

 

[Hugh Jaleak]

Eggy smell is likely to be hydrogen sulphide, (H2S), caused be decomposing organic matter and found in sewers. Nasty stuff, can soon kill you in high enough concentrations, so if you can smell it thats a relief as once it gets past a certain concentration it actually anesthetises your sense of smell so you no longer can detect it! Small concentrations will also disperse more easily when the premises are ventilated.

Dry weather will naturally result in less flow through the drains, and again, there will be even less flow at night time (unless raining), so that allows stagnant waste to collect, giving rise to H2S. In years past sewers were often flushed during dry weather periods to wash through any build ups of gunk to prevent the formation of H2S as much as possible, but the water companies dont want to spend money on flushing now.

If tests have come back showing the drains are airtight then it does beg the question is there a build up of pressure in the drainage system, but if the system is vented via a stack pipe then I would expect any excess to be vented off. Do you have a vent open to atmosphere on the property?

 

[Tom10001]

Hi, thanks for replying. no pressure release was the drainage company's suspicion too. but the main stack leads above roof level and is vented.

Not sure if my system is airtight - when they bunged the main pipe and filled sinks and the toilet, there was no water leak, but when they did a smoke test in the manhole in the back garden, we could smell the smoke in the downstairs WC (this was before the drain was lined). Don't know if that's normal or not or if the smoke would come through now its been lined.

The problem is that I can't tell if the smell comes from one area - like the toilet (which leads off the kitchen) or if it seeps through from anywhere else in the kitchen. kitchen floor is solid concrete base and ceramic tiles.

maybe i should call the water company as well

 

[Hugh Jaleak]

Ah, now thats interesting. If you could smell smoke in the downstairs WC when the smoke test was done, then H2S could get through too. No telling without doing a test on the drain if the lining operation has now rendered it airtight, (but I'll hazard a guess it hasn't!) Water company may not be interested, if the drain only serves your property, then whilst in runs under your property, it's your responsibility I'm afraid.

When the CCTV survey(s) were done, was there any indications of dips in the pipework, where waste could/did collect?

 

[Tom10001]

You're totally right about the water co. I called them at 4pm and they appeared at my door at 9pm with no warning! Anyway, not their problem, but they suggested getting stack pipe flushed out. (Not sure about that as its only 2 yrs old).

Nothing of interest on the cctv when they did it - no real dips or any pools collecting. I was surprised how clean and empty it looked. Water co said maybe the waste from the toilet needs flushing ?? Made no sense to me. But said the pipe leading to the main soil pipe could be unclean. Sounds odd to me.

I'm going to get the downstairs toilet (hung on wall concealed cistern) taken out and see if they can find anything going on. Loose seal maybe?

 

[Hugh Jaleak]

I'd consider doing an air test first, if there is a leak then its worth taking things apart to try and seal it. Otherwise you could just make things worse. The system should be airtight throughout now its been lined, assuming this was done properly, so if it fails a test on the underground section you need to be asking the lining company why!

 

[Tom10001]

Well, only the main pipe was relined. The junction off the main pipe which then leads to the toilet wasn't. But it didn't leak when he tested this section for leaks with a bung.

I'm clueless about this but how can smoke get through if there's no leak?

Either way I'll get another smoke test done.

Maybe I should get this junction lined too.

Christ. It's like burning cash.

Thanks again for your help.

 

[Hugh Jaleak]

Unfortunately with older houses, come older drains, and often the salt glazed stoneware used in pre 1950's builds is now no longer at its best. Pipes crack and move over time, resulting in problems, some of which you are now experiencing. If the pipe is accessible its sometimes easier to replace with plastic, but I'd look at a test and/or CCTV survey before committing to any further expense.

 

[Tom10001]

thanks I will have it checked. for what it's worth all the pipe work inside is under 5 yrs old and the old mains pipe is now re-lined. I just don't know why non one can find the source.

The smell is only there in the morning and it's only briefly there - so its an emission from somewhere rather than a persistent smell and its related to the hot weather.

Today, it wasn't in the downstairs at all and instead the upstairs bathroom had it and I could also smell it on the landing, in a spot where there are no bathrooms or water pipes (other than for the rads) the whole system is vented, everything drains well. what else do I do to get to the bottom of it??

 

[Nige F]

Smells will travel up boxings/ducts through small holes in walls etc. Something I discovered in a large old hotel I worked @, (found an open drain pipe in the basement) your kitchen floor is solid - are the other ground floors, or are they wood?

 

[Tom10001]

Update:

I'm still getting the cabbage / sewer smells on a daily basis - as before they only come first thing in the morning in the kitchen, downstairs toilet and now upstairs toilet. They disappear as soon as I open a window.

What's new and I didn't mention in my first post is that the downstairs loo also had a separate horrid smell, been getting worse and worse. Like very strong urine. Finally I got the toilet taken out and the plasterboard it was hung on taken down. Massive rats nest behind it - it was covered in crap and urine.

So far, so grim. I found a small gap where the pipes from the boiler we're going into the sub-floor space. They must have come up from there. I've thoroughly cleaned and bleached the area - toilet no longer smells but the sewer smell first thing in the morning remains!!

So now I'm wondering:

- are the rats related to the foul sewer smell? (The two smells were always independent. One was constant the other was only ever there in dry weather)

- could the sewer smell be decomposing rats in my sub-floor? What would they smell like. And Then why only when the weather is dry and why only first thing in the morning? Seems v unlikely to me

- could a rat have chewed through something? If so why didn't any pipes leak when the drainage company tested them?

(Nige F - all the other floors are engineered wood on ground and carpeted floorboards above.

Any help greatly appreciated.

 

[Newboy]

The presence of rats (and the H2S) suggests that there is an opening into the foul pipework.

Is the floor in the toilet suspended timber (floorboards over joists) or solid screed over concrete.

If it's a suspended floor then I would suggest that removing a section and having a close look at the foul pipework would be the next move.

 

[Tom10001]

i'm not sure to be honest - the toilet floor is tiled, but I think there's a void beneath. I could remove a section - I'd do anything at this point - but I've had 3 separate camera surveys - and I'm about to get one company back to do another - so we've had a good look at the pipework.

See my first post above - the original pipe work had a few cracks and a small hole - but this has all been lined now. since then, the smell now appears upstairs as well as downstairs - god knows why

someone isn't picking something up - I just can't figure out what it is!!

 

[Hugh Jaleak]

Rats could be related to the smell, if there's a breach in the drain, they'll use that as a front door. I suspect the lining would be of the cured in situ resin sock type, Ratty will soon chew through that if it takes his fancy, so dont rely on it to solve the problem if vermin are present. Have you had a smoke test done again yet?

 

[Tom10001]

I guess they came in through the uncapped junction or one of the holes in the main pipe. It is resin you're right.

They have caused a stink, which is still localised in the toilet area. Repeated bleach and scrubbing hasn't got rid of it yet!

But the other HS2 smell is definitely different. This morning it wasn't that bad but then when the shower was on it got a lot worse. it smelt like the water going down the drain was forcing the gas up into the room.

If I didn't know better I'd swear the stack pipe had a blockage somewhere. The main bit of it other than the top section is brand new though.

I'll ask for a smoke test on the weekend. What should the correct result be? Zero presence in house and smoke emerging from top of stack?