Smell from toilet ONLY after heavy rain.

[Mattd]

Not really DIY, but looking for advice as to the possible reasons behind the foul smell that emits from two toilets after heavy rain.

A while back I had a local construction company make some alterations to the house, which included an additional two bathrooms complete with toilets, when it rains heavily, both of these toilets have a nasty smell that comes in to the whole house.

Both bathroom toilets have their own completely independent septic tank and drainage pit system, the drainage pit is basically like a well, so the excess water from the septic tank flows over in to this and it drains off in to the land at the bottom of the drainage pit, this arrangement is the same as the older (existing) toilet waste system, the bad smell is only coming from the two newer toilets, the old ones (3 in total) are fine and never been a problem in this way.

At first they plumbed in the waste (grey) water drainage from the sinks, showers and floor drains in to the septic tanks, so when the smell first happened, I had them redo all of those to the drainage system that was already in place for the existing grey water drainage, now none of this grey water goes in to the septic tanks at all, as that is where I first thought the smell could be coming from, through the floor drains.

 

In theory no smell can get through the water trap in the toilet, unless the air is trapped and it vents via the toilet?

There are vents on the septic tanks, that should vent the foul air out to atmosphere, I also fitted another extra vent in to the main waste pipe from one of the toilets to allow any possible excess foul air to vent via this rather than the toilet, it doesn't seem to help much ? 

The only common thing for the two newer toilets is that the toilet themselves are the same model.

 

Anybody experienced this before and can give me any clues as to why this smell happens and what I can do to resolve it?

[lopburi3]

The air vent needs to be at the toilet - the septic tank/pipe is under water when you have heavy rains so can not vent.  There should be a pipe on drain from just below toilet to allow air vent - but if water get up to toilet outlet level that will also be blocked - French drains with pump to get water off your lot is an alternative solution.  Also might prevent flooding if properly planned (your property is a ship that bails water faster than it can enter).

[Crossy]

Do you have floor drains in the rooms? These are invariably installed with no traps and can be the source of 'orrible smells. A small plate upside down over the drain will stop the smell if that's the source.

 

Also check if your toilet pans have vent holes round the back, some tape over the hole will allow you to verify if that's the source.

 

[55Jay]

Some reading while you're waiting for other comments. 

https://www.thaivisa.com/forum/topic/994063-drain-smells-from-toilet-in-new-house/

 

I recall an odor at my mate's house in a Pattaya moo baan, it could make you feel dizzy.   Was coming from a ground floor shower drain which, I believe, was connected to the street gray water drain. 

 

[Mattd]

Thanks for the replies.

1 hour ago, lopburi3 said:

The air vent needs to be at the toilet - the septic tank/pipe is under water when you have heavy rains so can not vent.  There should be a pipe on drain from just below toilet to allow air vent - but if water get up to toilet outlet level that will also be blocked - French drains with pump to get water off your lot is an alternative solution.  Also might prevent flooding if properly planned (your property is a ship that bails water faster than it can enter).

 

1 hour ago, Crossy said:

Also check if your toilet pans have vent holes round the back, some tape over the hole will allow you to verify if that's the source.

I will have a look at the back of the toilets and see if this vent exists, the property is well drained, so flooding is not an issue at all.

 

1 hour ago, Crossy said:

Do you have floor drains in the rooms?

Yes, these are the ones that I had re-piped so that they drain directly to a waste water system that is all around the house, the floor drains from the 3 other older bathrooms also drain in to the same system, I have tried covering them before and it makes no difference, the smell is definitely a toilet waste smell, so is coming from the tank or toilet, it is only when it rains heavily, when no rain or light rain the smell is not present at all.

 

The below pictures are of one of the septic tank system from outside.

 

The smaller cap on the left is the drainage pit and the septic tank itself is under the big cover.

 

In this picture, from left to right, grey water pipe for the sink and floor drains (2), Water supply pipe, toilet waste pipe complete with the additional vent I inserted at the top and lastly the main vent pipe, the smaller pipes are electrical conduits.

[lopburi3]

1 hour ago, Crossy said:

Do you have floor drains in the rooms? These are invariably installed with no traps and can be the source of 'orrible smells. A small plate upside down over the drain will stop the smell if that's the source.

 

Also check if your toilet pans have vent holes round the back, some tape over the hole will allow you to verify if that's the source.

 

Actually these type drain/traps have been available here for decades; but indeed many do not bother to pay a few baht extra.  But they do need to have water in them so if not filled when cleaning or taking shower you may have to add water for evaporation.  Also if become full of dirt need to be cleaned out.

[stud858]

I've had to lift two toilets up before. They weren't sealed properly at base Not only that, they weren't aligned properly.

Matching the holes and applying a good silicone glue seal fixed bad smell and improved flush.

[Mattd]

OK, just had a look behind one of the offending toilets and cannot see a vent at all, at least above floor level.

I would have thought that the tank itself would have to have a vent of some sort and this is where I assumed the vent that I mentioned in the above picture is from, otherwise how does the tank fill if the air cannot be purged out of it as it fills?

[Mattd]

1 minute ago, stud858 said:

I've had to lift two toilets up before. They weren't sealed properly at base Not only that, they weren't aligned properly.

Matching the holes and applying a good silicone glue seal fixed bad smell and improved flush.

Thanks, that is an option I am considering to see if it helps, was also thinking of perhaps trying a totally different model of toilet.

[Psimbo]

6 minutes ago, stud858 said:

I've had to lift two toilets up before. They weren't sealed properly at base Not only that, they weren't aligned properly.

Matching the holes and applying a good silicone glue seal fixed bad smell and improved flush.

You beat me to it- I considered a loose seal and nothing around the base as well. Silicon sealer worked for me.

 

Great minds think alike.

[Psimbo]

4 minutes ago, Mattd said:

Thanks, that is an option I am considering to see if it helps, was also thinking of perhaps trying a totally different model of toilet.

It's likely the seal- the water trap would stop odors (and hopefully crocodiles) seeping into the pan. give the silicon a try first.

[Mattd]

1 minute ago, Psimbo said:

It's likely the seal- the water trap would stop odors (and hopefully crocodiles) seeping into the pan. give the silicon a try first.

Yes, I will definitely give this a go, what puzzles me though is why this only happens during heavy rain, otherwise there is no smell at all.

I agree that the water trap should stop odors, but it is possible for air to vent up through the trap if it is under pressure, which is why I wondered if it was due to the rain entering the tank and forcing air out.

Next opportunity I'll get both toilets lifted and reseated, then see what happens.

[Mattd]

35 minutes ago, lopburi3 said:

Actually these type drain/traps have been available here for decades; but indeed many do not bother to pay a few baht extra.  But they do need to have water in them so if not filled when cleaning or taking shower you may have to add water for evaporation.  Also if become full of dirt need to be cleaned out.

The floor drains are of a similar type.

 

[stud858]

I lifted my toilets because the flush was bad too. If your flush is OK. I would just run a bead of silicon around the base without lifting it. Clean with alcohol first and make sure you seal it perfectly all around.

 

Bolt holes too

[Pogust]

Me think water fill up in the last drainage tank during heavy rains and push air backwards through the septic and up to toilets. And someone forgot the seal under the toilets.

[SomchaiDIY]

Stink toilet thailand i have much experience on this problem from many year in hotel and resort repairs

 

Heavy rain not good for septic tank installed at close level of area water tables - many Thai house have this trouble because no test on land and house level made before building

Seal between toilet outlet and septic pipe very important must be gas seal but many thailand builder do not care much about this seal

 

Connection to septic pipe best to use the wax or rubber ring seal but not all toilet brand have this and many builder throw away

 

Thailand builder will try to seal edge of toilet to stop gas leak but this is poor fix repair

 

Many times I see construction worker not measure correct location of toilet pipe from wall and later make a problem for fixing toilet to make good seal from gas

!! Always best idea is fix join between toilet and septic pipe - not waste time with vent hole in pipe or silicon on toilet
 

[Esso49]

When did you last have the septic tanks pumped out ?

[lopburi3]

3 minutes ago, Esso49 said:

When did you last have the septic tanks pumped out ?

He said they were brand new - and if working right (you are not adding something to kill bacteria) should seldom, if ever,  require any pumping out.

[bankruatsteve]

If the smell is not constant and occurs when a storm travels through, it is likely due to atmospheric pressure changes.

[sirineou]

7 hours ago, stud858 said:

I lifted my toilets because the flush was bad too. If your flush is OK. I would just run a bead of silicon around the base without lifting it. Clean with alcohol first and make sure you seal it perfectly all around.

 

Bolt holes too

 I can understand not wanting to lift the toilet, it is a pain in the ass job, but if the smell is coming from the toilet bowl it means that a positive seal between the toilet and the drain pipe has not being accomplished with a wax ring. Sealing around toilet base with silicone will prevent water and smell from entering you bathroom but not from soaking your bathroom floor slab and could eventually cause some concrete damage especially if there is slab mesh steel nere by.

 The proper way IMO is to lift the toilet place a proper size wax ring and seal between the Toilet bowl and the drain pipe.

  

[Esso49]

4 hours ago, lopburi3 said:

He said they were brand new - and if working right (you are not adding something to kill bacteria) should seldom, if ever,  require any pumping out.

Utter rubbish , most Septic tanks in Thailand are not even 2 stage let alone 3  and best practice here , as in  the UK, is that they recommend a septic tank should be emptied once a year (As a general rule of thumb, it's recommended that you have your septic tank emptied roughly once a year, although if you live alone or in a very small household, you may get away with having your septic tank emptied bi-annually if, for some reason, you can't get around to having yourtank professionally emptied. )

 

Now the poster has said they were new , but also stated during heavy rain they smell. That suggests that whilst new when they were installed they have been in duty during more than one period of heavy rain.   Did by any chance the builder connect the grey water outlet to the septic tanks or even storm water  from guttering.  If so they will fill up pretty quick.   Of course we don't know the size of the tanks either.   However get them pumped out,  cost about 300 baht.   When they are clean run your sink to determine if they are being filled by grey water ( they shouldn't be ).   Then flush the toilets to ensure sewer water is discharging to the tank correctly.

[bankruatsteve]

A "septic tank" implies a septic system which, under normal use, should never need emptying.  A cesspit is not the same and requires periodic waste removal.

[Esso49]

18 minutes ago, bankruatsteve said:

A "septic tank" implies a septic system which, under normal use, should never need emptying.  A cesspit is not the same and requires periodic waste removal.

Complete and utter rubbish.  Think you are confused somewhat with maintenance  and perodic removal of sludge which is required.   I pasted the guidelines in an earlier post.  For yours and others enlightment please read this link. https://www.gov.uk/guidance/general-binding-rules-small-sewage-discharge-to-a-surface-water

 

That is a generalised statement and offers the reason as to why they need emptying periodically. Thailand does not have a national standard for sewerage discharge from domestic properties so with all outr house constructions I always recommend following the UK standards. 

 

Irrespective of that the poster has a smell.  I have provided advice as to how he can identify the correct plumbing for his sewerage discharge and hence attempting to identify the cause of the smell.   From experience in Thailand this is caused through a full tank ( by whatever reason), or an incorrect or blocked atmospheric vent ( and yes automatic vents can be a problem) or else in the worst example the toilet discharge pipes are leaking/not installed correctly ( often a problem with Thai "builders")  so that during heavy storms the ground water pushes the leaking effluent (that should have gone to the tank) to the surface and hence the pong.

 

Needless to say that there should be a separate tank for grey water from the sinks with a grease trap preceding its discharge into the tank.

[taninthai]

11 hours ago, stud858 said:

I've had to lift two toilets up before. They weren't sealed properly at base Not only that, they weren't aligned properly.

Matching the holes and applying a good silicone glue seal fixed bad smell and improved flush.

This ...I didn’t have to actually lift my toilets..as the Thais had cemented them down...but a blob off silicon over the holes that are used to screw the toilet to the floor cured the bad smell from mine.

[bankruatsteve]

11 hours ago, Esso49 said:

Complete and utter rubbish.  Think you are confused somewhat with maintenance  and perodic removal of sludge which is required.

Insult aside, I concede that sludge buildup does need removal.  In my total of 20 years living with a septic system in 3 different places, that turned out to be "never" and with no issues.  My point was that even when a "septic" tank is used, my observation of almost all installations I've seen here, is that it becomes a cesspit because there is no effort to make it a septic system (leach field, etc.).

[lopburi3]

Actually in cities drain is normally made into public drain system and have normal septic tank/overflow/drain or the single tanks that are split inside into two chambers.  And in over 40 years have only pumped several times due to construction rather than being full.  Have 3 systems and 6 toilets for 8 to 10 people.  

[Mattd]

12 hours ago, Esso49 said:

Now the poster has said they were new , but also stated during heavy rain they smell. That suggests that whilst new when they were installed they have been in duty during more than one period of heavy rain.   Did by any chance the builder connect the grey water outlet to the septic tanks or even storm water  from guttering.  If so they will fill up pretty quick.

As per my OP, the grey water discharge from both of the newer bathrooms were originally connected to their respective septic tanks, I had the builder change this, so these discharge to a separate grey water system that is common to the whole house.

In answer to your question, so far these two have never been emptied, each tank serves one toilet and they are not used daily by any means.

 

16 hours ago, bankruatsteve said:

If the smell is not constant and occurs when a storm travels through, it is likely due to atmospheric pressure changes.

Interesting theory, it is only during heavy rain, light rain doesn't cause the smell.

I am going to have to spend a little more time investigating how the tank vents, they must be a vent, otherwise it couldn't fill up and actually, the drainage pit should also have some sort of vent in theory.

As per other posters suggestion, I will look at having both toilets resealed as well.

[stud858]

On the matter of sewerage,

The two condos I reside at while in Thailand let their treatment well breakdown. Raw sewerage ends up down the city street drains. One of the condos got a foreigner manager who reconditioned the motors and panel and got treatment working again. The other condo still letting crap run into the street drains. I'm guessing a lot just let their treatments go to buggery.

The poo poo farty smell doesn't seem to bother some.

[Esso49]

13 minutes ago, Mattd said:

As per my OP, the grey water discharge from both of the newer bathrooms were originally connected to their respective septic tanks, I had the builder change this, so these discharge to a separate grey water system that is common to the whole house.

In answer to your question, so far these two have never been emptied, each tank serves one toilet and they are not used daily by any means.

 

Interesting theory, it is only during heavy rain, light rain doesn't cause the smell.

I am going to have to spend a little more time investigating how the tank vents, they must be a vent, otherwise it couldn't fill up and actually, the drainage pit should also have some sort of vent in theory.

As per other posters suggestion, I will look at having both toilets resealed as well.

I am stating the obvious here but the vent you added to the toilet discharge as shown in your picture, it is sealed well ?  And that particular vent has what at the top to prevent ingress of rain water ?  The reason I ask is that from the photo,  that horizontal section of pipe prior to entering the 4" discharge does not look horizontal , rather falls back rather than having a fall to the discharge pipe ( Apologies if it is just my wrong interpretation from the photo). So the reason I asked about the the top of the pipe and rain water ingress was due to the potential "puddling" in that pipe and hence impacting the venting action.

 

Guess you cannot check the pipework for leaking or incorrect installation ?

 

Have you lifted the access to the septic tank and removed the septic tank cover ? Please do so and shine a torch inside ( while holding your breath perhaps !! ).  What do/did you see ?

 

 

 

[Mattd]

57 minutes ago, Esso49 said:

I am stating the obvious here but the vent you added to the toilet discharge as shown in your picture, it is sealed well ?  And that particular vent has what at the top to prevent ingress of rain water ?  The reason I ask is that from the photo,  that horizontal section of pipe prior to entering the 4" discharge does not look horizontal , rather falls back rather than having a fall to the discharge pipe ( Apologies if it is just my wrong interpretation from the photo). So the reason I asked about the the top of the pipe and rain water ingress was due to the potential "puddling" in that pipe and hence impacting the venting action.

 

Guess you cannot check the pipework for leaking or incorrect installation ?

 

Have you lifted the access to the septic tank and removed the septic tank cover ? Please do so and shine a torch inside ( while holding your breath perhaps !! ).  What do/did you see ?

 

 

 

The additional vent is as sealed as it can be using the PVC pipe glue, at the top of it is a Tee piece to stop rain entering, the section of horizontal pipe that you see on the picture is to allow the pipe align with the other vent upright, this was installed purely as a test to see if it would help reduce or stop the smell and it is only on one of the toilets, it hasn't made any difference.

Apart from what you see in the photo, the rest of the pipework is buried under concrete and tiles, so difficult to check properly.

I will do as you suggest with the septic tank when I get home later in the week.

 

The more I think about it, the more I do think it is a bad installation, as when it was in the midst of being built I visited the Farang boss's house and there was a definite toilet smell there, at the time I foolishly didn't register this.