Hotel style "septic" tank - how to fill in?

[TravelerEastWest]

Hotel style "septic" tank - how to fill in?

Our chung came up with a plan to dig a rectangle the size of a car roughly. Note we have lots of family and house guests...

Double layer brick walls with a center wall to make two chambers the center wall has a circular hole that connects the two chambers.

There is concrete on the top and bottom with metal reenforcing. Also a small hatch that can be opened if need be.

Toilet water only goes to the first chamber, shower to the second.

This was described to me as a hotel type septic tank.

Between the outer brick wall and the earth is a gap which is going to be filled in with sand for the first 50cm.

We have lots of broken red bricks and broken floor tiles and concrete roof tiles left over from building.

(1) Can we use all the broken stuff to fill in the sides of the septic tank combined with sand and earth or should we use all sand?

(2) Has anyone used this hotel style septic tank before? Normally I read on TV about plastic or concrete ring septic tanks not much about brick and poured concrete types.

[Crossy]

Well it sounds fairly conventional.

Where is the outlet of the second chamber draining to? It should go to a drain field although many local systems empty into a local water course

Filling between the outer wall and the ground can be anything that will fill the gap, a good way to get rid of broken bricks, tiles etc, but do make sure the hardcore is broken small and mixed in with sand etc so it does fill the gap.

[bankruatsteve]

I don't know how it can be 'septic' without a leach field. Maybe the hotel model is different somehow?

If enclosed in concrete, it doesn't matter what you have on the outside for fill. A leach field would have gravel beneath a pipe with holes in it.

Edited February 9, 2014 by bankruatsteve

[sirineou]

I don't know how it can be 'septic' without a leach field. Maybe the hotel model is different somehow?

If enclosed in concrete, it doesn't matter what you have on the outside for fill. A leach field would have gravel beneath a pipe with holes in it.

Perhaps the system is not described well by the OP, The second tank would need to have some way for the water to leach in to the ground,

Two ways:

First,as you described a leach field. The most desirable option IMO, if there is adequate space for it, because a leach field discharges water near the ground surface, and aside from water being absorbed by the ground, discharge is also aided by evaporation.

Second, the walls of the second tank would need to me perforated, so that the water will be absorbed by the surrounding ground.In such system it is not a good idea to throw all the tile and brick scraps around the walls of the second tank, because they will impede the absorption of the water discharge by the ground.

You want the ground around the second tank to be .as permeable as possible, thus the sand.

[TravelerEastWest]

Well it sounds fairly conventional.

Where is the outlet of the second chamber draining to? It should go to a drain field although many local systems empty into a local water course

Filling between the outer wall and the ground can be anything that will fill the gap, a good way to get rid of broken bricks, tiles etc, but do make sure the hardcore is broken small and mixed in with sand etc so it does fill the gap.

Both chambers have concrete for the corners, floor and top (two top openings one for each chamber) - everything else is two brick walls with some space between the two brick walls.

Outside the outer brick wall is empty space for 6+ inches then clay soil.

The current plan is 50 cm of sand then a mix of broken tile, brick etc with sand and soil at the top.

Both tanks will slowly flow into the ground via the permeable wall and sand/broken brick etc mix. At that is the theory.

As mentioned above the walls are not plastic or cement.

The theory behind the brick and tile pieces is that will create air space although this will also result over time in settling?

[Crossy]

Allowing the first (black water) chamber to leech to ground is most definitely not a good idea, little or no decomposition will take place, potential for polluting the ground water. The first chamber MUST be sealed so the bugs can do their work and start breaking down the effluent.

Allowing the second (grey water) chamber to leech to ground is better, but a proper leech-field is the correct way to go.

On clay, you're going to get very little soak-away effect, time for a re-think of your drain arrangements I suggest.

EDIT This page has some useful information and diagrams http://35.8.121.139/edmodule/water/wtrfrm21.htm

[TravelerEastWest]

Allowing the first (black water) chamber to leech to ground is most definitely not a good idea, little or no decomposition will take place, potential for polluting the ground water. The first chamber MUST be sealed so the bugs can do their work and start breaking down the effluent.

Allowing the second (grey water) chamber to leech to ground is better, but a proper leech-field is the correct way to go.

On clay, you're going to get very little soak-away effect, time for a re-think of your drain arrangements I suggest.

EDIT This page has some useful information and diagrams http://35.8.121.139/edmodule/water/wtrfrm21.htm

The first chamber is sealed with concrete my mistake in my description - apologies.

The second chamber has a concrete layer on the top, bottom and corners.

I am not overly worried about a proper leechfield at this point as the size of the two chambers is far bigger than what we need - worst case is every few years I call a pump truck...

[Beardog]

Or way worse every 2 months, Bunch of people out my area that are to poor to pay attn to having a proper drainfield. Otherwise you are stuck with a cesspit which is just a holding tank waiting for the honey truck every 2 -3 months to suck up & it can be costly if it isn't the govn. trucks sucking it up. Seriously you are not saving Jack all & in the end you will need to dig it all up & do it right. Do it right once, It should last 25-30 years no maintenance do it wrong & you will soon be a believer in what you should have done in hindsight. Our neighbor at 1 month & 3 weeks already had to have the honey truck come out. Inadequate leech field. I tried to clue him in but he was stubborn & brainless & his following 3 contractors told him he needed as well, but he would only do it his way which was the wrong way. Don't be like him it's not a pretty picture & no happy ending.That left over red brick can be used with in the drainage field along with the gravel . What you have is the typical Thai cesspit thought by the builders to be a real septic system. The design has been recycled many years & no one ever has gotten a proper education in how to build it correctly & the way your design is as others stated you risk contaminating the groundwater.

Edited February 10, 2014 by Beardog

[canopy]

Excellent post Beardog. He doesn't have a septic system at all and seems content to make things up as he goes with a broken system that will work poorly. It will cost more money and headaches in the end but that's just the normal way people do things here. Maybe someone else in the future will heed the excellent advice you provided.

[wayned]

You'l be surprised how fast the gray water tank will fill with your showers and washing machine draining into it. Once it is filled and the drainage is not proper it will overflow back into the first tank and both tanks will fill. Then your toilet won't flush, your septic system will not work properly and you'll have to have the tanks pumped often.

Believe me! I learned by experience. I built my house 15 years ago and the worst problem that I had was drainage. I had a proper septic tank with an overflow into a cesspoool and the gray water draining directly into the cesspool, but no overflow into a leach field. The ground is clay and after both tanks fuilled they both had to be pumped often. I finally unhooked the gray water drains to the cesspool and have them drian directly into a leach field. Everythings works fine now and I have not had to have the cesspool pumped since. The septic tank should always remain full to let the "bugs" do their job.

[TravelerEastWest]

You'l be surprised how fast the gray water tank will fill with your showers and washing machine draining into it. Once it is filled and the drainage is not proper it will overflow back into the first tank and both tanks will fill. Then your toilet won't flush, your septic system will not work properly and you'll have to have the tanks pumped often.

Believe me! I learned by experience. I built my house 15 years ago and the worst problem that I had was drainage. I had a proper septic tank with an overflow into a cesspoool and the gray water draining directly into the cesspool, but no overflow into a leach field. The ground is clay and after both tanks fuilled they both had to be pumped often. I finally unhooked the gray water drains to the cesspool and have them drian directly into a leach field. Everythings works fine now and I have not had to have the cesspool pumped since. The septic tank should always remain full to let the "bugs" do their job.

I appreciate the extra comments but the size of the two chambers is far bigger than what we need so is unlikely to be an issue in the near future.

We have a number of these hotel style septic tanks and none have a washing machine connected.

But more importantly I agree with the leech field comments but the septic tanks have already been built and time does not allow more construction now.

[Crossy]

TEW, your OP implied you had no experience of this type of tank, you now say you have 'a number' which is it? Are they all designed the same way, with no leech field? How often do you need to empty?

Where do your washing machines drain to? Nothing to stop you draining shower and basin waste to the same place, you could even put it on the garden, it won't be filling your grey water tank then.

[TravelerEastWest]

TEW, your OP implied you had no experience of this type of tank, you now say you have 'a number' which is it? Are they all designed the same way, with no leech field? How often do you need to empty?

Where do your washing machines drain to? Nothing to stop you draining shower and basin waste to the same place, you could even put it on the garden, it won't be filling your grey water tank then.

Crossy,

I have a grand total of 4 all built at the same time (a couple of months ago) but until a few days ago not filled in hence this post - so the answer to your question is that before this build zero experience with this type of septic tank - at no time did I say that I had some before...

(Living in Thailand I find that one has to pick one's battles. This build was done with Thai relatives involved with giving lots of free advice and labor and chungs doing the building. Next time I will hire a civil engineer for construction supervision.)

All are designed the same way with no leech field.

My best estimate is that it will be about 3 years before they need to be emptied if we use the second chamber for shower water. If not then much longer.

The washing machine drains into empty land (we are not in a city) And has only been in use for a few days. I am planning on using a natural biodegradable soap and a new machine that will use less water and energy.

The shower water may very well end up in the garden area if I am sure that the soapy water won't be harmful - about 500 trees so far have been planted and a vegetable garden in the near future. But I will need to do composting on a large scale which is a new topic and one that will be more fun...

On a side note you will be happy to know that we have some nice Schnieder boxes for breakers and moving 3 phase power around.

[Crossy]

Ok, now I understand.

I think you're going to be surprised how quickly they fill, but that's your choice and problem.

You do have access so the honey-wagon can get to the tanks don't you?

[PeVee1st]

I built my house with 2 systems. Gray water to 2 tanks, 1 tank connected to all non sewer outlets and then overflow to 2nd tank. When 2nd tank is full it is pumped onto the lawn. Very small pump, so not use much electric.

Septic water to 2 tanks with similar construction to gray water system.

Never had septic tanks full & never had to pump out.

I live on clay soil. No odour problems as septic is sealled.

Been in use trouble free for 6 years now.

Sent from my GT-I8160 using Thaivisa Connect Thailand mobile app

[passingas]

Please query septic systems in this forum. It has been posted before. If I were you, I would run all Grey Water (shower and lavatory...even washing machine water directly out)...not into your septic system. The chambers (in a built septic tank) allow for a scum layer, which is tiny microbes...to do their work. If you use the sanitary tee system (as explained in previous posts) you will allow a scum layer to form (without separate chambers) and not drain out due to gravity (slope) You will want the output pipe of the tank about 5 cm lower than the input (to allow for said drainage). I am in an area of hard pan clay (great rice farming area...holds water like an ocean) where a leach field was not an option....therefore I incorporated an extra aerobic (air infused [via a large volumn aquarium pump]) tank to take care of residual crap that the anaerobic (primary tank) tank might not be able to take care of. It works like a dream...You can still incorporate the sanitary tee piping arrangement into your hotel style tank and not have to deal with chambers. Good luck....pg

[TravelerEastWest]

Thanks everyone for your ideas - amazed that septic tanks have such interest.....

The septic tanks are finished - my only question was about how to fill in around the tanks.

I was not involved with the construction much at all as I often hear the phrase - "too much"...

So I am focusing my attention on the electrical system and a few other areas.

There are two possibilities:

1) The septic tanks will take two plus years before they need pumping - in which case all is well

or

2) They don't work - then we pump more often and or consider rebuilding with a better design.

[northengr]

As a Licensed Engineer having designed a few hundred of these systems for the regulatory environment in upstate NY, I could add a few things to the mostly good comments already here.

The normal design basis for water usage in a home is between 40 and 50 gallons per day per person. That is about 200 litres if my merican conversion is right. Where water is free, some numbers are really higher, few are lower, and americans take fewer than the 3 showers a day many thais take. In NY, we size the septic tank (anaerobic digestion and settling) for minimum of two days water flow. Here is it considerably warmer and would digest faster, but settling time would be similar so don't make it too much smaller.

Outflow from the tank is the non-standard part of any system. Depends so much on the soil depth and perc. Usually its shallow trenches or a leach bed with perforated pipe distribution and crushed stone with filter fabric on top to keep it separated from the 6 inches of topsoil over it. This crushed stone is doing two things distributing the fluids across the whole bottom ot the absorption area and also providing a medium for the aerobic microbes to reside and attack the passing smelly anaerobic effluent from the septic tank. A course uniform sand might also work, but it would clog more easily.

So if there is no outlet and no percolation into the ground you will be filling the tank pretty fast. Clay will not perc and in fact what little water it does absorb will expand the volume significantly from dry up to wet. Think of all the cracks you see in drying farm fields. This expansion could easily push a lot on the walls of the tank if you are soaking the area around that tank, just like freezing ground does in northern climates.

I have often wondered what a tested perc rate for soil here might be where it appears fairly clayey. In the extreme it will perc zero. A normal leach field of 5 rows of 2 foot wide (60cm) trenches each 60 feet long (almost 20m) seems large, but in poor soil it is often required. In great soil it might be a small leach bed of 3m by 6m. all stome and pipe headers.

All of the above costs money and takes space and now you know why the sewage runs down the gutter here.

End of sXitty subject

[sirineou]

As a Licensed Engineer having designed a few hundred of these systems for the regulatory environment in upstate NY, I could add a few things to the mostly good comments already here.

The normal design basis for water usage in a home is between 40 and 50 gallons per day per person. That is about 200 litres if my merican conversion is right. Where water is free, some numbers are really higher, few are lower, and americans take fewer than the 3 showers a day many thais take. In NY, we size the septic tank (anaerobic digestion and settling) for minimum of two days water flow. Here is it considerably warmer and would digest faster, but settling time would be similar so don't make it too much smaller.

Outflow from the tank is the non-standard part of any system. Depends so much on the soil depth and perc. Usually its shallow trenches or a leach bed with perforated pipe distribution and crushed stone with filter fabric on top to keep it separated from the 6 inches of topsoil over it. This crushed stone is doing two things distributing the fluids across the whole bottom ot the absorption area and also providing a medium for the aerobic microbes to reside and attack the passing smelly anaerobic effluent from the septic tank. A course uniform sand might also work, but it would clog more easily.

So if there is no outlet and no percolation into the ground you will be filling the tank pretty fast. Clay will not perc and in fact what little water it does absorb will expand the volume significantly from dry up to wet. Think of all the cracks you see in drying farm fields. This expansion could easily push a lot on the walls of the tank if you are soaking the area around that tank, just like freezing ground does in northern climates.

I have often wondered what a tested perc rate for soil here might be where it appears fairly clayey. In the extreme it will perc zero. A normal leach field of 5 rows of 2 foot wide (60cm) trenches each 60 feet long (almost 20m) seems large, but in poor soil it is often required. In great soil it might be a small leach bed of 3m by 6m. all stome and pipe headers.w

All of the above costs money and takes space and now you know why the sewage runs down the gutter here.

End of sXitty subject

^^^^^^ Excellent post on the subject.

only one thing to add

In Thailand where except for the rainy season, is very sunny, though the perk rate might be bad, it's affect can be mitigated by evaporation if the leach field is located in a sunny area.

I read one post reply, where the "Gray water" was directed to a separate holding tank and then sprayed on the lawn via a submersible pump, this might be a good way to decrease the amount of water directed in to the septic tank.

and something that I will consider when we build our new home.

[TravelerEastWest]

Update so far no problems at all...

Also in our case the tanks are large probably around 8000 liters for each double tank and we have 4 sets.

We also have limited space for a leach field.

So it is quite possible that the design as is will work very well for us.

I am a big believer in Western technology but it is not always best in all cases...

Edited February 18, 2014 by TravelerEastWest

[Beardog]

Update so far no problems at all...

Also in our case the tanks are large probably around 8000 liters for each double tank and we have 4 sets.

We also have limited space for a leach field.

.

I am a big believer in Western technology but it is not always best in all cases...

Well you almost got it right except for So it is quite possible that the design as is will work very well for us

Substitute it may work for a while till rainy season

And I am a big believer in Western technology but it is not always best in all cases...

Substitute it for I am a true believer in western technology as it always works & the calculations are done

By math majors that have made a lifelong commitment to calculus & algebra to make sure the tanks are joined to

drainage fields to insure that the percolation calculations are always right.

You still built a cesspit not a septic & the drainage field could have been built in a very tiny area.

It can be built in a maze a circle 3-5 short legs or even downwards.

No matter what you bought yourself a bill of damage goods & by doing the job poorly you will have problems.

And the real question you have to ask is why you would ask on any DYI forum for a professional solution knowing you were not going to do it the right way anyway. The better question would have been to ask how can I build the leach field

in a small area. Everyone could have told you the same answer. While there are different ways to achieve perfect results

it does take doing the job right once so you don't feel stupid later .And get to re-do it anyway down the line.

Edited February 19, 2014 by Beardog

[TravelerEastWest]

Update so far no problems at all...

Also in our case the tanks are large probably around 8000 liters for each double tank and we have 4 sets.

We also have limited space for a leach field.

.

I am a big believer in Western technology but it is not always best in all cases...

Well you almost got it right except for So it is quite possible that the design as is will work very well for us

Substitute it may work for a while till rainy season

And I am a big believer in Western technology but it is not always best in all cases...

Substitute it for I am a true believer in western technology as it always works & the calculations are done

By math majors that have made a lifelong commitment to calculus & algebra to make sure the tanks are joined to

drainage fields to insure that the percolation calculations are always right.

You still built a cesspit not a septic & the drainage field could have been built in a very tiny area.

It can be built in a maze a circle 3-5 short legs or even downwards.

No matter what you bought yourself a bill of damage goods & by doing the job poorly you will have problems.

And the real question you have to ask is why you would ask on any DYI forum for a professional solution knowing you were not going to do it the right way anyway. The better question would have been to ask how can I build the leach field

in a small area. Everyone could have told you the same answer. While there are different ways to achieve perfect results

it does take doing the job right once so you don't feel stupid later .And get to re-do it anyway down the line.

BearDog,

You clearly have not read taken the trouble to read what this topic is about. At no time did I ask how to build a leech field or anything similar.

Your comments are not amusing or helpful.

If you had taken the time to read you would understand that no other options were/are currently possible.

This is Thailand sometimes you simply need to accept life here. At least I do - maybe your life is very different...

I think an apology is in order.

I did not build or design anything or even pay for it...

[Crossy]

Sadly TEW, I believe BD is correct, you have a cess pit and it will need emptying more often than you think. How full is the tank as of now?

With no leech route (unless the second tank construction is different to what we are understanding and is permeable) all the water that goes down each time you flush is going to stay in the tank. Add to that the filling effect of the wet season and you may end up with a stinky problem

[Beardog]

Update so far no problems at all...

Also in our case the tanks are large probably around 8000 liters for each double tank and we have 4 sets.

We also have limited space for a leach field.

.

I am a big believer in Western technology but it is not always best in all cases...

Well you almost got it right except for So it is quite possible that the design as is will work very well for us

Substitute it may work for a while till rainy season

And I am a big believer in Western technology but it is not always best in all cases...

Substitute it for I am a true believer in western technology as it always works & the calculations are done

By math majors that have made a lifelong commitment to calculus & algebra to make sure the tanks are joined to

drainage fields to insure that the percolation calculations are always right.

You still built a cesspit not a septic & the drainage field could have been built in a very tiny area.

It can be built in a maze a circle 3-5 short legs or even downwards.

No matter what you bought yourself a bill of damage goods & by doing the job poorly you will have problems.

And the real question you have to ask is why you would ask on any DYI forum for a professional solution knowing you were not going to do it the right way anyway. The better question would have been to ask how can I build the leach field

in a small area. Everyone could have told you the same answer. While there are different ways to achieve perfect results

it does take doing the job right once so you don't feel stupid later .And get to re-do it anyway down the line.

BearDog,

You clearly have not read taken the trouble to read what this topic is about. At no time did I ask how to build a leech field or anything similar.

Your comments are not amusing or helpful.

If you had taken the time to read you would understand that no other options were/are currently possible.

This is Thailand sometimes you simply need to accept life here. At least I do - maybe your life is very different...

I think an apology is in order.

I did not build or design anything or even pay for it...

I would offer an apology but you seemed to miss the point entirely. Every person that gave you advice has been offering this exact advice for anyone on TV DIY forum since as far back as 2004 that I can remember. If all of us didn't believe in the exact method on how to build a septic system then you might need an apology.

However since you could have even dug the dimensions down & not cost any space or build it around in a circular fashion you were being somewhat foolish to not give a shit about what everyone told you to do. Ignorance is one thing ....when you don't know everyone does or has done this. Stupidity is when you take the time to get the right blueprint for success & just don't use it to save a couple baht now & play kick the can down the road later.

Seriously I have never seen a septic build that you could not make some sort of drainage field in a very small or tight area.

Not that it matters that much but I am sure everyone of the posters feel like your post was a waste of time & effort where we could have helped someone that wasn't so poor he couldn't pay attention. This ones for you bud. Your the one that screwed the pooch & are trying to justify sheer stupidity.

You learn a lot from some of the sharp minds on the forum but you do have to try a little bit.

[TravelerEastWest]

Bear Dog

I won't rise to the bait and will let you go on your own way.

[Somtamme]

TEW, if you haven't got sufficient area of land for a drainage field, then the only option is a packaged treatment plant, one which is designed to treat the effluent to allow this treated discharge to go to surface water. The Thai planning authorities will not take kindly to such a shoddy installation as proposed. What will happen is partially treated sewage is going to go septic pretty quickly and cause complaints. How you've explained your proposals is no where near the commonly accepted minimum standard where public are concerned.

[TravelerEastWest]

TEW, if you haven't got sufficient area of land for a drainage field, then the only option is a packaged treatment plant, one which is designed to treat the effluent to allow this treated discharge to go to surface water. The Thai planning authorities will not take kindly to such a shoddy installation as proposed. What will happen is partially treated sewage is going to go septic pretty quickly and cause complaints. How you've explained your proposals is no where near the commonly accepted minimum standard where public are concerned.

The planning authorities were fine with the plan and provided building permits

The house is finished

The are are no problems at all so far.

We are not in a big city or mooban there is no one nearby to create complaints - so basically there is no public to be concerned about.

Keep in mind a point already made - we have much more capacity than is needed so any design shortcomings will most likely not be an issue.

Another point already made - I did not design, construct or pay for the build. My request for advice was for how to fill in the outer layer - this has been answered and the project finished.

If there is a future problem it will be dealt with then.