Dear Experienced builders,

Until recently i assumed these structures were put in place to temporarily collect water to aid building as i notice they disappear after the building was completed.

I even had an argument with my spouse that it was not really possible for it to be submerged later until i noticed one out of the two that's been constructed adjacent my residence had submerged and was severing as septic tank!

Please can someone educate me on this?

Am following the one that is still on the surface as i want to see when it would "disappear" submerge

mufutau55, spyder880 and others you are needed here o

Its very simple. They will sink it by digging the sand around it. Just watch them when they are at it..lol

Sir cos the area is a waterlogged area and excavation can't go far cause of water dere so wat they will do is to construct the septic tank on surface and get the help of those that sink it down

Today, they pumped water out of it and I noticed serious digging inside.

nnemak:
Today, they pumped water out of it and I noticed serious digging inside.

Yes they will sink it... meaning they will dig holes inside it gradually it will go down and be buried.
Then they will pump out more water and then lay plastic and put a concrete on the bottom to seal it tight.
This kind is required in a waterlogged area where blocks cannot be used.

Check this thread below from Page1 to Page3 to see the whole process from the beginning to the end.

https://www.nairaland.com/2004074/reconstruction-diary-5-bedroom-bungalow/1

Hajji M.

Thanks , I understand both the concept and method now.

mufutau55:


Yes they will sink it... meaning they will dig holes inside it gradually it will go down and be buried.
Then they will pump out more water and then lay plastic and put a concrete on the bottom to seal it tight.
This kind is required in a waterlogged area where blocks cannot be used.

Check this thread below from Page1 to Page3 to see the whole process from the beginning to the end.

https://www.nairaland.com/2004074/reconstruction-diary-5-bedroom-bungalow/1

Hajji M.

nnemak:
Thanks , I understand both the concept and method now.

Good. We are all learning sir.

Hajji M.

IT'S SEPTIC not spectic

addicted to nairaland : some wake very early to be FTC

Informative

I can't yet get the process

Usually used when the land is waterlogged because it will be ordinarily impossible to dig and cast due to ground water.

I want to know too

[b]Luckily I have cast and buried very many of such tanks. And I want to explain it in very plain manner.

Remember that in the villages and in many towns, to do your soakaway, you just dig the ground and use blocks to build the walls of the soakaway inside the dug pit. Then you turn some blocks so that the waste liquids can flow through the holes of the block into the soil. Then the solid waste is left inside the soakaway.

But in towns and cities where the water is very near like in lekki and VI, if you do that normal soakaway, the water from the ground will turn it into a swimming pool in just 1 day or 2! You cannot use blocks to do the walls because the water pressure plus earth pressure will collapse it inside the ground. And even before then, water would pass through any holes allowed into it.

But people in the house must poopoo. So the best solution builders adopt is to cast the whole thing on the ground after reinforcement and carpentry works. We use waterproof admixture to improve the water resistance of the structure. We also plaster it and apply felting to it (if the client doesn't over negotiate).
Thereafter, some guys your are expert in SINKING septic tanks enter inside and continually dig and dig until the entire structure reaches the required level. If you don't engage a good plumber and a land surveyor, they may sink the tank below the required level therefore making it not work properly. Or they make it to be too high that it would not flow with the compound level.
So after sinking it, you will start seeing water inside like swimming pool except you did it in very dry season. You use 2 or 1 pumping machine to bail out the water to the point that it becomes very dry. Then suddenly you seal the bottom using DPM, chemicals and cement mortar. That sealing stops the water completely. They way you seal is systematically. You seal one side and allow space for water to pass through another place until the sealing dries. Then block that hole and run your rebars and cast fast fast fast.
Please don't try this at home. Because many who we explain like this to jump to "Do It Yourself " and they mess up the whole septic tank.

Any septic tank done wrongly will get full easily and they will have to pump the sewage out every 6 months or 9 months or even 3 months. A good one will last very long before needing a pump. The waste water can have its own compartment or just to flow into the public drain. I mean water from kitchen and bath etc.

After the bottom, the top slab is cast using formwork and rebars also. There must be openings with precast concrete cover. Your interlocking should pass over the tank if you got the level perfectly. Also don't let the pipes to run into the septic tank at middle point. Because most Nairalanders whose site I went to correct, the sewerage pipes enter the tanks at middle so it get full easily. They got the slope wrong from the manholes and Inspection chambers. [/b]

It's septic

Usually common in states like bayelsa. And some parts of delta, where the soil is too loose to hold itself when excavation is done. In other words in swampy areas.

Based on my experiences as a certified ..... The plumber will make use of ship-pumping machine from the house it is meant for and channel it to the tank. #lobatan. Very simple arithmetic!!!

it works noni

wow modern day septic atnk

ifeoluwasegun:
I can't yet get the process

Na wa for u o

Whoa

masterblogger:
IT'S SEPTIC not spectic

Lol, you even noticed it...thumbs up

my friends hotel n waterlogged ibeno akwa ibom used same approach

I am using it in my rented apartment here in Ajah Lagos. 95% of building in Island have it. So, no be new thing!

This is nice

opalu:
[b]Luckily I have cast and buried very many of such tanks. And I want to explain it in very plain manner.

Remember that in the villages and in many towns, to do your soakaway, you just dig the ground and use blocks to build the walls of the soakaway inside the dug pit. Then you turn some blocks so that the waste liquids can flow through the holes of the block into the soil. Then the solid waste is left inside the soakaway.

But in towns and cities where the water is very near like in lekki and VI, if you do that normal soakaway, the water from the ground will turn it into a swimming pool in just 1 day or 2! You cannot use blocks to do the walls because the water pressure plus earth pressure will collapse it inside the ground. And even before then, water would pass through any holes allowed into it.

But people in the house must poopoo. So the best solution builders adopt is to cast the whole thing on the ground after reinforcement and carpentry works. We use waterproof admixture to improve the water resistance of the structure. We also plaster it and apply felting to it (if the client doesn't over negotiate).
Thereafter, some guys your are expert in SINKING septic tanks enter inside and continually dig and dig until the entire structure reaches the required level. If you don't engage a good plumber and a land surveyor, they may sink the tank below the required level therefore making it not work properly. Or they make it to be too high that it would not flow with the compound level.
So after sinking it, you will start seeing water inside like swimming pool except you did it in very dry season. You use 2 or 1 pumping machine to bail out the water to the point that it becomes very dry. Then suddenly you seal the bottom using DPM, chemicals and cement mortar. That sealing stops the water completely. They way you seal is systematically. You seal one side and allow space for water to pass through another place until the sealing dries. Then block that hole and run your rebars and cast fast fast fast.
Please don't try this at home. Because many who we explain like this to jump to "Do It Yourself " and they mess up the whole septic tank.

Any septic tank done wrongly will get full easily and they will have to pump the sewage out every 6 months or 9 months or even 3 months. A good one will last very long before needing a pump. The waste water can have its own compartment or just to flow into the public drain. I mean water from kitchen and bath etc.

After the bottom, the top slab is cast using formwork and rebars also. There must be openings with precast concrete cover. Your interlocking should pass over the tank if you got the level perfectly. Also don't let the pipes to run into the septic tank at middle point. Because most Nairalanders whose site I went to correct, the sewerage pipes enter the tanks at middle so it get full easily. They got the slope wrong from the manholes and Inspection chambers. [/b]

Allow me add this to elaborate your good idea

Good thinking, good result.

After the whole process you have