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Question about Septic Tanks


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We're having a new home built in the rural Northeast Issan country...

 

The house has TWO bathrooms, built side by side, and TWO SEPTIC TANKS, also dug side by side. Fortunately, the water table of the soil is, I believe, rather deep.

 

Originally, the builder was going to port the toilet water AND the sink/shower water from each toilet... into the SAME septic tank (associated with that bathroom).

 

Given the fact that the fumes from the tank would be free to vent back into the shower (no inherent air trap) AND IMPORTANTLY the fact that there is CERTAIN to be abundantly MORE waste water from the shower and sink...  I thought it would be wise to port the TOILET water from BOTH bathrooms into ONE septic tank, and all the other (Gray) water from the shower and sinks... into the SECOND septic tank.

 

As an aside, I thought it would be possible, should the gray water septic tank fill up to the top, that it could be force pumped out into the yard, to water the plants.

 

The builder agreed with my request to assign one septic tank as black water, and the other septic tank as gray water, and said he would plumb the feeds accordingly.

 

My question, to our illustrious group here, is... Do you think I was correct in requesting this black vs. grey septic tank design?

I'd appreciate any advice and real life experience stories to confirm or reject my thinking on this.

Thank You!
Pawpcorn

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Posted (edited)

Where is your water going AFTER the septic tank?

 

i am building a house now,
we have one septic tank for each toilet
black water to septic tank (then septic tank to soakaway)
grey water direct to soakaway (by-passing septic tank)

the soakaway is usually made of those concrete cyclinders

Edited by patman30
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Posted (edited)
17 minutes ago, Pawpcorn said:

(Gray) water from the shower and sinks

In Issan (If possible) they seem to connect Gray water--to the nearest storm water drain.

Or as put the nearest soakaway

 

 

Edited by sanuk711
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Posted (edited)

Thanks for both your answers... (and questions).

 

(Our 2 "septic tanks", as I was calling them, is really just TWO of those concrete "soakaways" you referenced, each one 4 cylinders deep. I had thought to call them "septic tanks", I guess in error, sorry about that!)

Your interest and responses helped me RE-open up the discussion with my partner, who has designed the house, and whose family construction company is constructing the house.

 

I TOO wanted to just let the gray water go into a trench of sorts, to just soak into the ground; it seemed simple enough.

 

BUT our house is adjacent another house, about 15 feet away, on that side... There IS no public works storm drain system in this rural farmland country area.

 

My partner has said repeatedly that just dumping the gray water out into a trench to just soak into the ground "would not be polite" to the neighbor.

However, with your feedback, it added some weight to my PRIOR "argument" (IE suggestions) to just let the gray water flow freely out into a shallow trench alongside the house... AND I REITERATED that (to the best of my knowledge) the water would NOT have any evil scent coming from it!

 

Anyway! NOW, (after the renewed discussion!) he has told me that he will discuss this situation at some length, with the building foreman (husband of his niece) in charge of the project... tomorrow.

 

1 hour ago, patman30 said:

Where is your water going AFTER the septic tank?

...well I guess I was using the wrong term, there are just TWO "soakaways", 4 cylinders deep, into the ground.

 

I had envisioned (IF NECESSARY) just pumping the gray water OUT of the potentially-filled graywater "soakaway", via an electric pump, into watering the plants in the back yard.

Thank you SO MUCH for both of your Reponses!!!

Pawpcorn
(second image below shows the adjacent house)

287686372_437692837920678_1703855672205331751_n.jpg

288388739_718289279278307_5540417966923864899_n.jpg

291145498_1159510317943211_5094728197828574844_n.jpg

Edited by Pawpcorn
added the current outside photo
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These are no septic tanks, these are just the ordinary cement rings that let the grey and black water sink into the ground. You should install a real plastic septic tank only for the toilets and let it overflow into one of those cement rings. The grey water from the showers and the kitchen can be directed directly into another tank of these cement rings. The overflow of these can be lead to the garden. Maybe dig a pit maybe 1 m deep and fill it with gravel. So the overflow will go into that hole. Of course it also depends on the soil condition. If it is very dense and has a lot of clay, it will be quite difficult for the grey water do seep into the soil. Just make sure that the overflows are not near a well location in order fo avoid contaminating the well water...

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36 minutes ago, Carlos Primeros said:

These are no septic tanks, these are just the ordinary cement rings that let the grey and black water sink into the ground. You should install a real plastic septic tank only for the toilets and let it overflow into one of those cement rings. The grey water from the showers and the kitchen can be directed directly into another tank of these cement rings. The overflow of these can be lead to the garden. Maybe dig a pit maybe 1 m deep and fill it with gravel. So the overflow will go into that hole. Of course it also depends on the soil condition. If it is very dense and has a lot of clay, it will be quite difficult for the grey water do seep into the soil. Just make sure that the overflows are not near a well location in order fo avoid contaminating the well water...

Thanks for the advice! Consultations with all of the above ideas and input will commence tomorrow! 

Thanks again,

Pawpcorn

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Posted (edited)
10 hours ago, Pawpcorn said:

Thanks for both your answers... (and questions).
(second image below shows the adjacent house)

287686372_437692837920678_1703855672205331751_n.jpg

 

 

You are vey likely to be over thinking the situation. The advice given re-actual septic tank (big black ball) will certainly do no harm.

the house I lived in for ten years prior to building my own had two of those ring thanks for the toilets. In 15 years they never filled up and were never pumped out, the current owners of the house have gone another 6 years with no maintenance requirements. The grey water was let outside with no treatment. Our soil is heavy clay so not the best for soaking away.

 

First step is to find out what the neighbours do with their grey water, it is very likely seeing the soil that it’s very absorbent and no pumps are needed

Edited by sometimewoodworker
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Posted (edited)
12 hours ago, Pawpcorn said:

Given the fact that the fumes from the tank would be free to vent back into the shower (no inherent air trap) AND IMPORTANTLY the fact that there is CERTAIN to be abundantly MORE waste water from the shower and sink...  I thought it would be wise to port the TOILET water from BOTH bathrooms into ONE septic tank, and all the other (Gray) water from the shower and sinks... into the SECOND septic tank.

Septic tank only takes from the toilet.

Shower and sinks water don't go in it so no fumes.

Which is why they only need one.

Edited by BritManToo
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12 hours ago, Pawpcorn said:

My question, to our illustrious group here, is... Do you think I was correct in requesting this black vs. grey septic tank design?

Of course you were right. A septic tank is one that is intended to hold toilet waste and can be from concrete, plastic or fibreglass. It is the starting point in a waste water system.

The standard Thai arrangement is 2 concrete tanks in the ground side by side, one for the toilet waste, known as black water, and the second for water from showers and basins, grey water. Overflow from the black tank passes to the grey tank and that can be leached or pumped away The gray water should never go into a black water tank and I am surprised the builder even suggested such an arrangement. Grey water invariably contains soap and detergents that upsets the biological process in the black water tank.

When I had my house built in 2009 I opted for plastic tanks, a cheaper option. With plastic tanks there is a difference between black and grey tanks with pipe connections and the black water tank has a mesh arrangement inside to help break down the solids. The builder installed the normal 2 tanks but shortly after I added a third myself to take the overflow from the grey tank. I pump the output from the system onto the garden and straight from the grey tank it smelled a bit, the third tank reduced that quite significantly.

Anyone starting off should be aware that you should put about 5kg of digester into the black tank to get the biological process started otherwise it will be necessary to empty the black tank on a regular basis. In over 14 years my black water tank has never been emptied.

What you can get away with will depend a lot on the planning department. Here in Chonburi they were quite strict and leaching on to the surface wasn't an option.

Good luck, building your own house is quite an experience.

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13 hours ago, Pawpcorn said:

Given the fact that the fumes from the tank would be free to vent back into the shower (no inherent air trap)

You still need traps and they have been available here for at least the last 50 years.  For sink drains use bottle trap - for floor drains use bell trap.  That is not clean water you are sending out and it will not smell clean if gas allowed to return.

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2 hours ago, sometimewoodworker said:

You are vey likely to be over thinking the situation. 

This IS my tendency, to be sure (as a life-long engineer).

 

The extension of this, now living here, is to take on the task of "planning for unforeseen circumstances", since that trait seems not to be a strong suit here, thus the abundance of "surprise" events occurring, due to ghosts, spirits, etc. 😉

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If you are going to get an off-the-shelf septic tank, make sure it has features like this one...

 

Much safer for you and your family than the open pit you have now.

 

 

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2 hours ago, lopburi3 said:

You still need traps and they have been available here for at least the last 50 years.  For sink drains use bottle trap - for floor drains use bell trap.  That is not clean water you are sending out and it will not smell clean if gas allowed to return.

I agree, a trap is No1 priority - it would be interesting to known why you aren't fitting one? 

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Example for ideas basic setups for septic + waste water system

 

This big house have recent modify work to septic + water system

 

Work include install new waste water trap tank and move final drain tank position after damage from big tree

 

This system has overflow on final drain tank connecting to street drain because level ground waters can make problems at rain periods

 

This system has 2 100mm pipe line from house  = septic + waste with air venting at line start

 

System location small garden area +30 meter from house
 

Tank areas after construction works

 

t1.thumb.JPG.cfd11c30175fd34a2524bfc0f0bfb882.JPG

 

 

Tank 1 2000 litre septics connect 5 toilet

 

t2.JPG.1754c5e8959819ab0d051ffc44d610c8.JPG

 

 

Tank 2 800 litre waste water trap tank

 

t3.JPG.b0d0368a947b71ed6a4bc91cd7c08336.JPG

 

 

 

Tank 3 cement 3 meter depth final drain + overflow

3 pipe = septic + waste + overflow

 

t4.JPG.adca194d0a50470d52340d6bb6833710.JPG

 

 

 

Tank 4 waste water box trap at kitchen stop some solid before tank 2

 

t5.JPG.c22d8906f291c1da5ade34b29c88d787.JPG

 

 

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29 minutes ago, Artisi said:

I agree, a trap is No1 priority - it would be interesting to known why you aren't fitting one? 

Educating the partner who is #1 lead guy for the house design... is a frequent task.

Just added THIS trap to my Lazada cart, and showed said partner the MANY many forms of vent traps, for shower drain, thank you!
https://www.lazada.co.th/products/qengjerng2394-backflow-preventer-toilet-sewer-plug-trap-insectproof-anti-odor-hair-trap-shower-drain-stopper-deodorant-floor-drain-core-i2663143943-s9581746455.html?

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Posted (edited)
On 7/2/2022 at 8:56 PM, Pawpcorn said:

I had envisioned (IF NECESSARY) just pumping the gray water OUT of the potentially-filled graywater "soakaway", via an electric pump, into watering the plants in the back yard.

This is not advised, the chemicals in any products you use may be bad for plants,

this is why Grey water does not go in the septic tank (which you don't have)
as chemicals in products kill the bacteria in the septic tank

you may want to get a packet of bacteria (like 40 baht), flush it down the toilet
it should help breakdown waste in the black water soakaway
but if you use chemicals in the toilet it will kill the bacteria
but as others suggest installing a septic tank (3000 baht) would be better (same applies about using chemicals)
 

Edited by patman30
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OP

Whatever you decide, do not allow the " Grey Water " from the showers and Kitchen Sink to ingress into the Septic Tank from the Toilet.

The Chemicals used for washing Dishes, Showers Etc destroy the Bateria inside a Septic Tank that works on the Nitrogen process.

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4 hours ago, Cake Monster said:

OP

Whatever you decide, do not allow the " Grey Water " from the showers and Kitchen Sink to ingress into the Septic Tank from the Toilet.

The Chemicals used for washing Dishes, Showers Etc destroy the Bateria inside a Septic Tank that works on the Nitrogen process.

Gotcha there, thanks for the reminder...

Now I wonder about the little plastic piggies I put in my current toilet to make the toilet water blue, and supposedly make the toilet easier to keep clean...

Do you know if these also destroy the Bacteria inside a Septic Tank that works on the Nitrogen process?

Thanks again,

Pawpcorn

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On 7/2/2022 at 8:56 PM, Pawpcorn said:

BUT our house is adjacent another house, about 15 feet away, on that side... There IS no public works storm drain system in this rural farmland country area.

My partner has said repeatedly that just dumping the gray water out into a trench to just soak into the ground "would not be polite" to the neighbor.

What has your neighbor have in place for water disposal.? 

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22 minutes ago, sanuk711 said:

What has your neighbor have in place for water disposal.? 

I will see if we can find out! They are not friends with my partner... but I will try to find out. 😄

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1 hour ago, Pawpcorn said:

Gotcha there, thanks for the reminder...

Now I wonder about the little plastic piggies I put in my current toilet to make the toilet water blue, and supposedly make the toilet easier to keep clean...

Do you know if these also destroy the Bacteria inside a Septic Tank that works on the Nitrogen process?

Thanks again,

Pawpcorn

There is only one way to keep that Nitrogen Cycle going.

That is not to place anything in the Toilet that should not be there naturally. ( unless a recommended product )

As an after thought

Make sure there is a soak away from the Toilet Septic Tank also

Many Thai builders do not understand the process of the Septic Tank, and after a Year or so they fail to work correctly as no provision is made for the Soak Away, and also they also allow "  Grey Water " into the Tanks 

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And never use the silly blue chemical things that people hang into their toilet cysterns. They distroy the bacteria in the septic tank. Also there should be an overflow of the septic thank which allows the now grey water which comes out of the septic tank to flow into a separate soakway made of cement rings. I have my septic tank now for more than 18 years and had not to pump out anything there. The precleaned grey water goes into one of the cement ring tanks and then I have an additional overflow of that one which goes further down into the garden. This is no problem here, because we are on a slope. So it drains well. We also have quite rocky and sandy soil (unfortunately) that helps to let the grey water soak into it. And if you want to do it really well, you should lead a 1,5" vent pipe from the plastic septic tank up the house wall to roof height and put a T-Fitting on top so the rain can not go down the vent pipe. With this you will not have any bad smell if the weather conditions are not so good.

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If you have a plastic septic tank, use chemicals as little as possible to clean the toilet because of the bacteria, there are also organic cleaning liquids which are bacteria friendly

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