Help - what is the stink?!

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I'm trying to find a plumber in our area that can come out within the next few days, but they all seem to be so busy!

We have a little ground floor cloakroom - just a toilet and a sink. Every now and again it STINKS - a really bad urine/sewage smell; like a neglected public toilet. No matter how clean I keep it, the smell stays for a couple of days and then goes away again. I finally want someone to come out to look at it because the smell has hung around for five days now.

What could it be? I'm worried that it's a cracked pipe somewhere inaccessible, or something that will cost a fortune to put right

Has anyone else had something similar and been able to get it sorted fairly easily?

We had a horrendous smell in our downstairs loo, which was more obvious on some days than others. It turned out to be dead rats in the ceiling space... Apparently it is a relatively common problem in extensions; when the new service pipes go live, the old ones are not always capped, so the rats have an easy time getting in from the drains. It did cost us quite a lot to get it sorted out unfortunately.

Following as have the same issue. Smell is predominantly in the room next to the downstairs loo, which has the soil pipe running down it, and only happens about once a fortnight.

We were about to get someone in in March, so that didn’t happen. Dreading a major issue as the builders who built this house were, not to put to fine a point on it, cowboys.

One minor cause of a bad drain smell can be lack of use. There needs to be water in the ‘trap’ in the pipes to stop smells coming back up from the sewers. If it all has a chance to evaporate, you can get a smell. We have a shower that is rarely used, and I go in there and run it from time to time to prevent this.

That must have been awful, @Knittedfairies - our smell is more of sharp urine stink; and it's not an extension . . . but then, I guess dead mice or rats could be in walls and little recesses and things; doesn't have to be a pipe.

@LadyScience I love our house but there are so many bodged jobs and bad DIY issues. The previous owners were incredibly lazy - they even painted around furniture, so when we saw the empty rooms, you could see the outline of bookcases etc. So, so shoddy.

@YesILikeItToo we had this exact issue with a bidet upstairs, and regular use resolved it. The cloakroom is used regularly, though, so I don't think under-use is the problem. It's more likely going to be something difficult and expensive

how old is the house

is the WC and drain original

is the floor wooden or concrete

if you sniff round the base of the pan, is that where it smells, and can you see any stains.

do you have any inaccurate pee-ers in the house.

is cleaning cloth, sponge or mop left in the room

is there a WC in the room above

Hi @PigletJohn - the house was built in 1996, the WC and sink are original (on our list to replace - but it's a long list!), the floor is wooden laminate, the room is too small and the smell is too strong to work out exactly where it's coming from, no inaccurate pee-ers (DH swears he's super-careful!), no cleaning gear in there apart from a bottle of bleach, and yes, the main bathroom is directly above the cloakroom WC.

so the soil pipe and waste pipes will be plastic

Under the laminate, is the floor concrete or wood?

Is there any sign of staining at the cuts and edges of the laninate?

Does the top of the soil pipe emerge from the roof with an open end, or has it been sawn off and boxed in, in the bathroom?

Can you see the duct in the corner of the bathroom and cloakroom, where the soil pipe is hidden? Can you see any way into the duct? (it might be accessible in the bathroom)

When you look at the house wall, on the outside, close to the soil pipe, are there any white or other marks, similar to limescale, round about floor or dpc level, on the brickwork?

is there a manhole cover nearby?

Has the bathroom configuration been altered since the house was built?

I'll come back with full answers tomorrow, @PigletJohn - I'll need to go outside for a couple of them and it's dark now. Thanks for pondering!

Hi @PigletJohn - if you're still around! I finally got round to finding answers to your questions. The smell has gone now - this happens every time; it reaches crisis point where I'm all "I need to get someone to look at this!" and then it goes away and something else breaks, which takes priority . . .

The floor is wooden under the laminate.

No sign of any staining on the laminate

Nothing is accessible in the bathroom - it's all been boxed off, there's no visible pipe work

I've taken photos of the outside so you can see the pipes. The upper window is the main bathroom and the lower window is the cloakroom bathroom. As you can see, there is a manhole directly outside.

Does that tell you what you need to know?

(And thanks so much if you come back and reply!)

Oh and to my knowledge, the bathroom hasn't been changed since the house was built!

thanks.

the soilpipe looks satisfactory. Do you have any visible gullies where rainwater downpipes or the kitchen sink enter the drains? Are they made of brown clay?

have a sniff round the airbricks. You can use a joss-stick or smouldering cigarette to see which side of the house the draught enters, and which side it exits.

I can think of a couple of possibilities

maybe the upstairs or downstairs WC has a leak in the trap or connector, at the joint or in a crack. It might be leaking into the floor un-noticed. Put some food dye into the cisterns (different colour in each) and look out for any stains.

or

maybe there is some blockage in the soilpipe, probably near the bottom. this is easier to check. Lift the manhole cover. is the pit empty? Get someone to flush the upstairs and downstairs WCs in turn. Does the water from each emerge swiftly into the pit, running quickly into the exit pipe, and dying away in ten seconds or so?

Depending on the age of your household, blockages may be toys, wallets, disposables, wet-wipes, sanpro or kitchen roll.

you can probably winkle up the lid by inserting a garden spade into the crack on one side, lifting it a fraction, then another spade on the other side. If it has oval lifting holes, you can use manhole keys

short
www.screwfix.com/p/monument-tools-115mm-manhole-keys-pair/14087

or long ones for heavier lids (measure the holes before buying these as some of this type are bigger for heavy iron lids)
www.screwfix.com/p/rothenberger-520mm-manhole-key-with-extended-handle-1-key-supplied/9638k

Slide the lid over the ground, no need to lift it up. Replace it after you have looked, to avoid anyone falling into it.

p.s.

I notice the ground round the manhole looks particularly damp and mossy, so look for any sign of a drip or leak.

You're an absolute star, @PigletJohn - thank you so much for taking the time to make those suggestions.

You don't happen to live in the north west, do you? We're planning some work