How often to empty sewage tank

[Gregjam]

How often do you need to empty the sewage tanks based on two people living in the house. Standard Thai build but no idea how large the tank is. Just over two years since we bought the new build and sure it has not been emptied.
I ask because apart from not getting a response from my Thai wife we have a problem with drain flies that appears to be linked with the floor penetrations under the two toilets in the house. I have ordered new penetration seals as I always doubt the build quality and know that the flies are breeding in the inaccessible area under the toilet bowl. The toilet will have to be lifted to clean this area and I don’t want any nasty surprises.
All advice welcome on tank emptying or drain fly extermination. I block all the other drains when not in use so know that beneath the bowl is the source.

[Nereus]

This has been posted about many times. A properly installed and operating septic tank system SHOULD not need to be pumped out before 5 to 7 years. But the problem in Thailand is that unless you built it yourself, there is no way of knowing just what is there.

Also, a lot of tanks get pumped out unnecessarily because people look into the tank and say;
“oh, its full”! Yes, it will look to be full, but it is what it is full of that matters! The tank will be full of water, and a “crust” will form on the top, which makes it appear to be full. Over time there will be a build up of sludge in the bottom of the tank, and if that eventually builds up to the surface the system will no longer operate correctly.

There are too many variables to be able to give an exact time. Usually, the first indication maybe a bad smell, or the flush cycle backing up.

Not had a problem with drain flies, but why do you think that they are breeding under the pedestal? The normal practice, even here, is that the pedestal sits on a rubber seal, sometimes called a “doughnut”, as that what it resembles. The stub of the drain pipe, (4” PVC) SHOULD also extend up into the base of the pedestal. Then the pedestal base should be sealed with silicon or grout around where it sits on the floor tiles. If they are in fact breeding under the pedestal, then it is more than likely that they have an escape route along the outside of the drain pipe.

[Dannie Boy]

Our septic tanks have been in operation for nearly 11 years and they’ve never been cleaned - I’m following the “leave sleeping dogs alone” philosophy!!


Sent from my iPhone using Tapatalk

[Gregjam]

I know they are breeding in the void between the floor and the bowl because I have one of those cameras for looking into small spaces and also by blocking off the openings in the back it vastly reduces the flies.
I have new floor seals just in case and as Nereus says I want to inspect the possibility of the being outside the pipe so will make sure that area is well sealed. The build quality is what I call standard Thai level which I will leave everyone to their own interpretation but most will be aware of what I mean. Only once I have checked it will I have any confirmation and be able to move forward.
As I have been pursuing this one aspect I took into account is the waste paper bin in the toilet to make sure it was emptied frequently.

[HHTel]

Only when the flush backs up do I have a septic tank emptied. The house is 18+ years old. 4 out of the 6 tanks have never been emptied. (used by toilets and bathrooms upstairs so gets little usage.) The 2 that serve the downstairs bathroom/toilets are extra large with 2 very large 'soakaways' positioned in line from the main tank. These have been emptied just twice, the last one being 3 or 4 years ago.
If they're built and installed correctly, they should be fine for years before they need emptying.
As for 'drain flies', never had a problem.

Septic tanks naturally promote bacteria which eats/breaks up the waste. Emptying your tank and cleaning too often will kill the bacteria and therefore lose the advantage.

[Gregjam]

Thank you for the responses. I would change the subject to Drain flies and how often…. but not sure if I can do that. While I am suspecting a build quality issue I have not ruled out a person issue. I spend long periods at work when my wife and Thai family are in the house. I also have strong suspicions that the flies may have got in either from the drains or possibly bred in a toilet paper bin that was not emptied for over a week due to infrequent use and they found the environment very suitable to their breeding cycle which is about a week. The void area underneath the plinth would have offered an ideal breeding spot hence them being there now. I have used duct tape to seal up one plinth and will do the other one today which should aid further investigations.

[brianks]

When I first came here 15 years ago finding a WAX toilet seal was a problem and I suspect most toilets were not installed with any and thus your fly breading problem. I don't think the Thai's know much about the necessity of a wax seal between the toilet and drain either. Today wax seals are easy to obtain a larger stores like Home Pro and Global House.

For Septic Tank: a farang builder told me to put a raw chicken into the tank as there is more bacteria in that animal than you can put in with any of the commercial additives. Takes about two weeks to "digest" in the tank and as long a the top of the water is bubbling, it's working. Keep from using disinfectant chemicals in the toilet as they kill the bacteria in the Septic Tank.

[HHTel]

If the tank is functioning properly, you should not need to put 'additives' into the tank. The bacteria will grow naturally as long as disinfectants and the like are not flushed into the tank killing the bacteria and therefore losing the benefit.
In 15+ years, I've never added anything to promote bacteria.

I'd never heard of the 'dead chicken' trick so I looked it up.

Q: I’ve heard that tossing a whole, dead chicken into my septic tank lessens the need to have the tank pumped because the bacterial action created by the rotting carcass is effective at breaking down sewage. True?

A: Like the Jersey Devil and other urban myths, this theory seems to have taken on a life of its own. I first learned of it in the late ’80s from readers who said they knew people who’d been using the technique for decades. I’ve also heard about people throwing in rotting hamburger meat or roadkill. Then or now, adding anything to your septic tank to stimulate decomposition is liable to have the opposite effect.

[Nereus]

I'd never heard of the 'dead chicken' trick so I looked it up.

This is only needed either from new, OR, after the tank has been pumped out.

[Nereus]

I know they are breeding in the void between the floor and the bowl because I have one of those cameras for looking into small spaces and also by blocking off the openings in the back it vastly reduces the flies.

I am completly confused by this statement. What "openings" in the back of what part? I assume that you are talking about a pedestal toilet, not a squat.

[Gregjam]

The toilet is a Cotto C126207 Mood to be precise, not a squat but a seated plinth type. I have bought two new floor seals (including the wax donuts in case that is the problem. The toilet is secured to floor mounts by two bolts (also in the kit ). At the back side of the plinth are some holes which allow access to the seat securing and flush tank securing bolts but this leaves the void space in which the bugs are thriving. The bathroom is the typical wet bathroom type which creates a more suitable breeding environment.
I am sticking with the plan to left the toilets so I can clean the difficult to reach areas and satisfy myself that the floor seal is not the problem.

[Scout]

If the floor seals were not working properly, most likely you would be experiencing very unpleasant odors building up in the bathroom. I installed a couple new fancy Korat toilets last year, had some seal issues but resolved them successfully. The installation instructions called for sealing the pedestal to the floor with silicone. That and a weekly puff of bug spray might fix the flies issue.

[Nereus]

At the back side of the plinth are some holes which allow access to the seat securing and flush tank securing bolts but this leaves the void space in which the bugs are thriving.

Really? There should be some form of seal between the tank and where it sits on the pedestal. Maybe worth removing the tank and checking there as well.