Bad smells in bathroom

19 Nov 2009
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United Kingdom
I have a victorian house with a septic tank - a large tank with soakaway.

My main bathroom's has an intermittent smell of sewer gas. We've removed an AAV from under the floorboards believing it to be the problem. A second AAV exists in the chimney stack of the bathroom.

The smell returned so we ran a vent pipe from our 3rd fl attic bathroom out through the roof (we did'nt have a vent pipe so believed this would solve the problem). However, the smell has returned smelling more like stagnant water than gas.

I am confident that the smell is not due to lack of cleaning.The toilet pan has always (2 yrs since fitting) had this 'stagnant' smell but seemed a small issue compared to the rotten cabbage smell. However, this smell is now filling the bathroom.

My builder suggests we run a 2nd vent pipe directly from the soil stack out through the wall and up to the roof . I am running out of ideas and may have to have the limestone tiled bathroom destroyed to find the fault.

Running water into the basin, bath and shower traps, hasn't made a difference either.

Our downstairs WC, and other bathroom on the other side of the house have no smells just the main bathroom.

Any suggestions? Thanks!!
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Monica, it's only recently that a AAV was permitted on a septic tank installation & having one 'below the floor' is quite disturbing!! Firstly I'd ask your ''Builder' if he's a fully qualified Plumber. As there's loads of cowboys around & on the face of it; it looks like you've had one in!!

You are quite right the smell will be from the drains, so get them to put in a soil vent pipe, venting the gasses.

Another problem I know of that can cause this problem in defective castings in the WC, you'd be surprised how a small pin hole can stink the place out!!
I hope that's of some help.
Lord Bothwell(The time-served toff)
Thanks for that. I inherited the septic tank with the house so the builder is not responsible (and is an ace bloke who I know and trust 100%). As I said, we have tried putting a vent pipe from the water pipes (not the soil stack) in the attic bathroom, through the roof, but the gas smell has been replaced by a stagnant smell. Could the toilet be the culprit then? As I say, the pan has always had a stagnant smell and that appears to be the smell now dominating the bathroom. I used to put those lemon loo blocks in the cistern but it just masks the problem. I have two similar toilets neither of which have any problems. Thanks.
What's the condition of your septic tank? Is there plenty bacteria activity going on??
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I have no idea. It is emptied annually, altho when we bought the house we were told that it could be done every 2 to 3 years. We prefer to keep it cleaned regularly. All the waste goes into it as we have no mains drains at all. It is an old klargester type, with a plastic diamond shaped cover. We had problems with the smell in the garden so this summer we had a bit of remedial work done which entailed re-bedding the hole on the lawn, and using grease to create a better seal around the lid. The garden smells have now seemed to stop. I have a waste disposal on my kitchen sink too, which goes into it. We don't flush any sanitary stuff ever, and I keep the use of bleach etc to a minimum. However, my washing machine, showers etc go into it too. We tried to buy a replacement cover for it but were told that the style was no longer available. I guess - but it is a guess - that it is maybe 12 to 15 years old. The house is over 150 years old but was renovated after a fire about 12 to 15 years ago. Thanks again!!
Have you tried contacting Klargester regarding a new cover?

I know the type you are referring to, the 'diamond' shape. These I believe were superseded by a rectangular steel cover and plastic frame, incorporating the two holes for the 'dip' pipes.

You dont mention having a dishwasher, but these can cause problems as the salt used to soften the water can affect the anaerobic bacteria operation in the tank if there is excessive discharge from a dishwasher.
I'm not saying that your septic tank is your only problem, but having it emptied every year is a bit bonkers. The tank needs to settle down & the bacteria needs a chance to grow in it, so with pumping it out every year you'll just remove any bacteria in there!!

I'd get it checked to ensure it's in a sound condition & not leaking. Then look on-line, as I'm sure there's some products available to enhance the bacteria growth.
I hope that helps?
I spent ages in the builders merchants trying to get a new frame and cover but the only one they could get had only one large hole plus one smaller hole for a (I guess) 4" pipe to stick through. My current frame plus cover has a large hole, about 18" or 24" wide, plus two separate 4" pipes sticking out. If we had bought the newer shaped frame and cover, it only had the large hole and one smaller hole and no-one at the suppliers seemed to be able to tell the chap in the merchants exactly why we had two small tubes on our exisitng frame and the newer frames only allowed for one to stick up. We therefore had no idea whether we would be causing ourselves a huge problem by not allowing access to all three holes. Sorry, does this make sense? So we decided to stick with what we'd got rather than try to put a frame with two holes over the tank that had three holes.
It depends how much use the tank is getting. Ive been out to plenty that have been long overdue for a desludge, the plastic Klargesters need to be done more frequently than the brick types due to their design. If overdue the outflow can have a higher concentration of suspended solids than it should which eventually clogs the soakaway. Come across a number where the inner divider between the 2 hemisphere's has collapsed into the tank, allowing the sludge into the outlet.

Klargester had changed the design on the later tanks, with the bottom hemisphere leading into a 'neck' which came up to the top of the access shaft, a far superior design in my view to the earlier types with the polystyrene ball blocking the access to the lower chamber. Seems to provide a more rigid divide too, which should alleviate problems with the divider falling into the tank.....

When emptying it is always advisable to leave 150mm of effluent in the bottom of the tank to 'kick start' the bacterial operation as the tank refills. You can buy 'bacteria' but if there is control over the level of detergents going into the tank then it may not be necessary to add anything and let nature do its job! Grease and washing powder in hard water areas doesnt help, it congeals and bungs everything up......
Lord Bothwell, Thanks for your reply. I am a complete novice where septic tanks are concerned and thought an annual clearout was a good thing. Obviously, I have misunderstood. So I am better to leave the tank alone if it is working? Are those bio/bacteria things worth investing in? We do have a dishwasher which uses salt (a suggestion from another posting - thanks). All of these things, I guess, might be adding to the bathroom odour in the initial stages, but the stagnant smell is another issue, I think. I will look for a company to service the tank so I can get an expert opinion. What a job!!
Still looking for help regarding stagnant smell, but now interested in help re septic tank issues.
Hugh, thanks for your post. This is all a bit technical for me.... we are a family of 4 using the tank for every bit of waste and water from the house. The tank has a soakway into a field at the back of our house (I think!!). Again, we inherited it when we bought the house and have no idea of the why's and wherefores. We have a washing machine, dishwasher, waste disposal on the kitchen sink and 3 bathrooms with wc's and one other WC. I do try to limit the bleach I splash around, but washing powder, fabric conditioner, shampoo, washing up liquid etc etc all go into the tank. I believe it is a plastic tank rather than brick built. What can I do to look after the health of the tank? Thanks.
I think with the amount of detergents and bleaches that we use these days, a septic tank has a hard time....anyway, in the good old days the tanks had two separate chambers, as well as the settling of these chambers was exposed to light, and the other kept in darkness to allow anerobic and aerobic bacterial action to take place. This is hardly satisfactory these days as most people just want to forget about these things. So long as the entrance and exit chambers are clear, just get it pumped out when it needs it. I've tried the various compounds available to help things along, but found no discernable difference in the tank contents. The golden rule is, only put stuff into the tank if you have eaten it first - with the exception of soft loo paper!
Anyway, thats not your problem regarding smell. I think you'll have to inspect all of the connections from the loo (including the pan coupler) to the outside manhole, and see that the connection from the chamber to the soil vent pipe hasn't come adrift somehow.
PS 2 of us in this house, large brick tank - pumped out every 4 years.
John :)
Thanks Burnerman. I will have to get a plumber to check those connections...trouble is the bathroom is tiled with limestone tiles, all around the bath boxing etc. Nightmare...this is why we are trying to sort it without taking the sledgehammer to everything. I am now going out and will check back later to see if anyone else has any ideas.
I certainly don't like the idea of AAV's - especially under the floor :eek: Has the one in the bathroom been removed too?
Much better to vent the SVP to the outside if you possibly can. Anyway these are really there to help with the dispersal of water (air behind it).
Do you ever get water sucked out of the wash handbasin / shower / bath traps when the loo is flushed? If you do, this is a sure sign that the venting isn't sufficient and a pong will result.
So, if the SVP isn't open to the atmosphere anywhere inside the building, the pong has to be coming from the connections from pan to waste somewhere along the line, I fear.
I hope you don't have to break up those tiles!
I used to bring in a septic tank bacteria enhancer from France - where there are lots of 'fosse sepitiques'. The product was called Eparcyl. I couldn't tell any difference when it was used here, so I don't use it now.
Be lucky! John :)

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