Sewer Vent causing odour outside

Colm R

Hey, I'm not sure if this is the correct forum for this issue I have - let me know if its suitable somewhere else.

Background to the problem. After purchasing a house last year, I drained the back garden, and installed a new septic tank - its the Oakstown BAF one. The tank itself is about 15 meters from the house. The site itself prevented it from being further away.

But, the area directly behind the house is lower than man hole covers for the tank. So I was finding in this area a really strong sewer odour which upset us both because of the investment we made in the system. Anyway, last night I went out to get to the bottom of this problem, and I'm now convinced the odour is not coming from the tank at all. Thankfully nobody saw me as I crawled around the ground sniffing. I'm also convinced that the smell is not coming from the ground pipework between the house and the tank.

And then there was a slight breeze kicked up, and the smell came strong again.

Attached is an image of the vent attached to the house. This is the original vent for the old system, and in the ground below this, new pipes connect to the old exit pipes from the house. This vent use to just handle toilet waste as there was a separate soak hole for grey water. Now this is a vent for all waste in the house.

As you can see, it goes above the level of the gutter. But I think because of a number of factors (the house is built in to a hill, and surrounded by large trees), the prevailing wind comes over the roof and then goes downward towards the ground behind the house, carrying the odour with it.

My first reaction is relief that the tank is not the cause. But now I would like to fix the cause. Any thoughts?

- it will not be possible to vent from within the house to the attic and onto the roof.

- is it possible to go horizontal under the gutter to the gable which will get it higher up. If so, how far can you go horizontal for?

- The house is a bungalow, so obviously its not very height currently.

Any thoughts?

Newgrange Warrior

May be a simple blockage. I have the same system and some funny drainage levels and manholes and I would get an odour from the vent periodically. It might be good to rod and hose out the pipes first.

Markcheese

Picture looks about right , as above check for blockages, do you get the smell worse when someone flushes the loo/ pulls the plug out ? Could there be a prob with any manhole covers, or drain inlets ( thats what happened to us dodgy manhole cover , run the tap , stink in yard )

sydthebeat

a vent stack should terminate min 900mm over the highest point of an opening into a building if that opening is within 3.0 m of the vent.
therefore your vent stack should be at least 900mm higher than the highest point of that rooflight, which it clearly isnt. Thats been a regulation since 1997.

Colm R

Cheers for the replies. I will check for blockages, but I suspect not, as I have regularly checked that the waste flows as expected through some of the new inspection chambers further out in to the garden.

I think the smell is at its worst when the washing machine or dishwasher do their work, although that might be because I'm outside while they are on. I'll certainly try to check these problems out.

As for the vent being below the window, well its an old house that I bought, and I'm fixing every problem one day at a time.

sydthebeat

It could be smells coming back in from the diswasher and / or washing machine.

Any chance of a pic of how the pipes flow from these?

Markcheese

sydthebeat wrote: »

It could be smells coming back in from the diswasher and / or washing machine.

Any chance of a pic of how the pipes flow from these?

Make sure there's a trap on washing machine and dish washer... But if the smell is outside in the yard then neither appliances or soil stack are likely to be causing a prob...

Markcheese

Actually if yr septic system is close to your house , could the smell be coming from it's vents when appliance is on ... Could you ring the installer and give out stink . Well ask them about it, or even get them to come out and tell you where the smell is likely originating from and how to fix it....

Colm R

Markcheese wrote: »

Actually if yr septic system is close to your house , could the smell be coming from it's vents when appliance is on ... Could you ring the installer and give out stink . Well ask them about it, or even get them to come out and tell you where the smell is likely originating from and how to fix it....

I'm almost certain that the smell is not coming from the tank itself. I've even lifted the lids at a time when I can get an odour in the back yard and can barely get a scent. At the same time, I've climbed up to the roof level and got the scent up there quite strong near the vent and this seems. When I smell it in the back yard, I do feel the breeze blowing gently downward from the vent.

I'm going to check for blockages tonight and see if I can figure anything out. I will keep ye updated.

The Big Gun

We had a problem just like that, drove me crazy trying to find solution. Engineer came up with zero. Eventually my dad came up with the solution.
Something similar to this...
http://www.mcmahons.ie/heating-plumbing/plumbing-supplies-heating/soil-vent/grey-pipe-fittings/air-admit-valve-4.html

Worked perfectly, haven't looked back since. Easy & cheap.
Let us know how you get on.

NIMAN

Big Gun, what does that do exactly? Is it like a carbon filter for the top of your vent pipe?

I am following this thread closely as I sometimes get a smell out my back too. It often appears when the washing machine is on as well.

The one thing I have noticed, and read about, is that a houses' vent/soil pipe is meant to be a 4" round pipe and be a little above the top of your guttering. Mine is a 3" square pipe, like one that would be used for rain collection guttering, so perhaps it ain't big enough to take the smell away? Also, it only goes about 1 inch above my guttering.

I am thinking of getting a 4" round put in to start with to see if that helps, before going to the hassle of getting the tank or pipes checked out.

North West

Hi Colm
See attached. This might also be the cause
NW

The Big Gun

Niman,

I'm not a plumber, but what this does is it releases air (for a very short period) only when there is enough pressure to release. I couldn't believe how quick & comprehensive it was in sorting our fowl sewer odour. It is available in other guises at all major plumber / hardware outlets. Maybe it is available for your size pipe, check with your best supplier. There must be an adaptor to fit this to your pipe, I'd try that before changing any pipes, if I were you. Let us know how you get on.

Colm R

Thanks guys for the suggestions.

Checked last night for blockages and there are no problems at all. When the toilet flushed, everything ran through as expected checking each of the inspection chambers along the router.

Even with the inspection chambers open, there was no odour at all from them. Which I think makes sense, because even with a constant breeze blowing down the roof, the affect of it comes in waves rather than constant. Some days there could be nothing at all.

I'm not an expert but I would put that down to whatever appliance or people are doing whatever in the house, and whatever part of the cycle my system is in.

Anyway, I remain convinced that its coming from the vent, because a) I can smell it up there most of the time, and b) most often I get the smell nowhere near the tank or any of the man hole covers or inspection chambers. I'm going to look into the air admit valve.

Cheers for the suggestions, I will keep you updated. Going to spend Saturday doing as much investigation as possible.

muffler

Colm R wrote: »

as there was a separate soak hole for grey water.

This should be going to your tank and also Id suggest extending the top of the vent pipe by another metre.

Colm R

NIMAN wrote: »

Big Gun, what does that do exactly? Is it like a carbon filter for the top of your vent pipe?

I am following this thread closely as I sometimes get a smell out my back too. It often appears when the washing machine is on as well.

The one thing I have noticed, and read about, is that a houses' vent/soil pipe is meant to be a 4" round pipe and be a little above the top of your guttering. Mine is a 3" square pipe, like one that would be used for rain collection guttering, so perhaps it ain't big enough to take the smell away? Also, it only goes about 1 inch above my guttering.

I am thinking of getting a 4" round put in to start with to see if that helps, before going to the hassle of getting the tank or pipes checked out.

Out of interest, what kind of system do you have. I think this is side effect of new systems, where grey water and and toilet waste have to go through the same system.
Whatever about toilet waste, grey water smells a lot worse. I know this from experience with the old soak hole, for the few months I used it before I got rid of it. It use to overflow on the driveway, and the smell was acidic and would burn your nostrils. Now this is going into the same tank as everything else.

Colm R

muffler wrote: »

This should be going to your tank and also Id suggest extending the top of the vent pipe by another metre.

It is going to my new tank now. It was not going to it until I bought the new system last year.

Newonhere

Hi I just moved into a new house and had a similar problem but in my case the odour was in the house (inside the en-suite), my plumber suggested fitting an Air Admitting Valve to the top of the vent pipe. As soon as I fitted the valve the odours vanished so the problem was resolved for about €45, very happy outcome

tred

Newonhere wrote: »

Hi I just moved into a new house and had a similar problem but in my case the odour was in the house (inside the en-suite), my plumber suggested fitting an Air Admitting Valve to the top of the vent pipe. As soon as I fitted the valve the odours vanished so the problem was resolved for about €45, very happy outcome

So when someone flushes toilet or there is a flow to the sewer the water replacing the air, causes a vaccum and that pipe opens. Just be aware that you are then limiting the air input to you tank system that might be used for bacteria growth etc. Be a lot cheaper do what someone said earlier first, add an adaptar to end of that vent, and extend it up a metre. I don't know how the air compressor works on the oreilly system. is it taking air from outside the tank or via the vent system....i know its on 24X7

NIMAN

Colm R wrote: »

Out of interest, what kind of system do you have. I think this is side effect of new systems, where grey water and and toilet waste have to go through the same system.
Whatever about toilet waste, grey water smells a lot worse. I know this from experience with the old soak hole, for the few months I used it before I got rid of it. It use to overflow on the driveway, and the smell was acidic and would burn your nostrils. Now this is going into the same tank as everything else.

Sorry it was already installed when we moved in, so no idea what type of system it is.

Colm R

Small update on this. I have been advised that getting a smoke canister will help me identify where there are leakages in the system.

So my plan is on the next available Saturday where there is a light or no breeze, and a smell, is to drop a smoke canister into the first inspection chamber after the soil stack. If I am correct, the smoke should rise through soil stack and then be blown back towards the ground.

If I am not correct, I should be able to identify other possible points where the smoke will come from.

Anyone every try this?

tred

Colm R wrote: »

Small update on this. I have been advised that getting a smoke canister will help me identify where there are leakages in the system.

So my plan is on the next available Saturday where there is a light or no breeze, and a smell, is to drop a smoke canister into the first inspection chamber after the soil stack. If I am correct, the smoke should rise through soil stack and then be blown back towards the ground.

If I am not correct, I should be able to identify other possible points where the smoke will come from.

Anyone every try this?

Good idea. Ideally a day the odour is strong as well..so smoke will follow same path!