first homes, any house in thai, have seen very few. even better hotels. love the aroma early in the morning at nice hotel. at least issue little rubber covers.

Been in a few hotels in bangkok that offer rubber covers...not complimentary though, but a good idea i suppose.

This toilet has a separate septic tank. its well covered, well, concreted in really apart from the access screw top of course.
I had a look yesterday afternoon, admittedly after the rain had stopped and it wasn't overflowing/filling up, will check when it rains and the bubbles start again.
We had all the tanks emptied about 2 months ago and this is the guest toilet so doesn't get used much.
Agree with above about the pipes sticking out of the front of shop houses, we used to live in a shop house and had one on each floor, they were overflows from the toilet cisterns and the watertank on the roof.

Kudjap

Have you checked to see if the breather pipe is open? This is typically a blue piece of pvc pipe sticking out of the ground somewhere close to the tank.

Mike, yes, we ran a metal tape through it all seemed clear.

Kudjap

Since this only happens when it rains I suspect it may be linked to the exit pipe from the septic tank to your street drain. If the street drain is backing up then you will probably have difficulty flushing your toilet.

Since this toilet is for your guests and doesn't get much use and you had it emptied about 2 months ago it should be nearly empty. Open the access cover to check to see if there is any liquid in the tank. If the tank is empty or nearly so I would assume the problem is between the toilet and the tank. If the tank is nearly full I suspect water is backing up into it from your street drain. Septic tanks here in Thailand do not typically use a drain field to overflow into but drain into the street drain.

Hope this helps

Thanks Mike,
We don't have street drains here in the booners....... the water / waste seeps into the ground.

I did take a look and the tank was nearly empty, but as I said this was after the rain had stopped. I can't see it filling up with rain (from where or how I wouldn't know) and draining that quickly. My thoughts exactly were a problem between the toilet and the tank. The pipe runs in the concrete floor in the toilet then outside agan in concrete into the tank. We don't get any dampness on the toilet floor so I don't think there's any leakage there nor do we get any outside again can't see any leakage signs....

Really baffling............

Kudjap

Is this a concrete ring type or plastic septic tank? Any chance you taking a picture or two of the area and send it to me? If the problem existed all the time I would say it is in the pipe from the house to the tank. But you say it only happens during a heavy rain which leads me to believe there is water getting into either the tank itself or the pipe from the house. Try opening the tank again and have someone flush the toilet. You should see a steady stream of water flowing into the tank. If you do not see water flowing into the tank you may have a break/crack in the line coming from the house. If the line coming from the house is in concrete chances are you will not smell anything. You probably will not see any dampness outside either because the line may be too deep and the water will naturally flow down into the ground.
Another thing to check for during the next heavy rain is what happens to the rain runoff from the roof and surrounding area. Does it naturally drain away from your septic tank or towards it.
I agree it is baffling but I'm sure solveable.

Sorry Mike do't have access to a digi camera but I will try with the TW's phone.
This is a concrete ring type tank in the ground, it has 4 rings so pretty deep, especially for a guest toilet only.
The pipe from the toilet is actually concreted into the floor and into the concrete from the house to the tank, i,e, not concrete on top of them, the pipe is only 3 or 4 metres from toilet to tank, the breather pipe is run up the wall of the house.
We have guttering runing round the roof to a water butt so the only rain that gets near to the tank is whatever hits the access point, which has a screw top with a good rubber seal.
Will have a look at the toilet flushing point you make when the TW gets home and post result. Also pray for some more rain to take a look inside when its actually raining.
Thanks for trying to help

My 2 baht worth: Our first rental had drains in the kitchen and bathrooms that smelled horrible. And, as the smell was the same in all places, I figured there was a single culprit. After some investigating, I uncovered some outdoor drain covers (small cement blocks) that revealed several years worth of kitchen drain sludge (old rice, grease, you name it) along with several years worth of shower sludge (lots of hair). Once we cleaned that out and kept the trash from going down the kitchen sink (and made a vow to never (not that we had ever) pee in the shower again) our problem went away.
Another thing that helps is a monthly treatment of EM (mix 150CC of EM with 150 CC of black molasses in 1.25liters of water......cap, then wait 7 days.........pour a cup down each drain before you go to bed).
90++% of the homes in Udon drain kitchen and shower wastes into an open drain (usually covered by small cement blocks along side the house). To make matters worse, most homes have no drain traps that prevent bad smells from entering the home.

What is "EM"?

Something called Effective micro-organisms. A liter costs about 100 baht and a liter of black molasses costs less than 50. All told, they will make over a 100 gallons of mix. Best place to buy it is directly across from Paolo's main entrance.....a few stores to the right of the Aussie Pub place as you're facing it. The guy speaks excellent English and will explain how to mix it. He'll probably also demonstrate/explain all the health benefits of EM (he drinks the stuff), but I just use it monthly in drains and in the toilets.