Used 2.5m3 Resin Plastic Tank Burial: Creating Concrete Encasement in Clay Soil & Maintenance

Hello,

I purchased a used 2.5m3 plastic tank (it looks like polyester resin). I want to bury it in clay soil so I have to weigh it down for sure. The shape of the tank is similar to a barrel (for vertical mounting) and I thought to manually dig a hole that would be wider than the tank by only a few centimeters on each side. I would pour a concrete slab under the tank and then pour it all over with concrete so that a concrete tank would be created around the plastic tank (not forgetting, of course, the reinforcement). While pouring concrete, I would of course fill the tank with water in parallel to equalize the pressure.
Maybe something I did not take into account? Is this really a good idea? (resin tank completely filled with concrete)
The tank is not new and I assume that as the resin ages, I could dry the tank every few years and put another layer of laminate on the inside to extend its life.

Constructive criticism greatly appreciated. Thank you in advance.

It seems to me that if you want, a concrete base can be made, but why pour concrete around it. What is the purpose of this outdoor concreting? The soil around the reservoir is enough.

You can fill the space with sand, the basic question is whether this tank is free-standing or not and requires reinforcement?

@ slavy2


This tank is actually a water meter pit (I plugged the holes). which is already in age. It was damaged on one side and I repaired it with a glass mat and epoxy resin. I do not know what the durability of the polyester resin (which the tank was probably made of) looks like, so I thought about reinforcing the structure with concrete. Unfortunately, the clay in my case is the worst (it reaches 12 meters) and that is why I counted that to compensate for the buoyancy of the tank, I would still need about m3 of concrete. I wonder if such a solution may have any negative consequences? (maybe, for example, resin and reinforced concrete 'work' differently or there is a risk that the water which, however, gets between the concrete and the resin, will freeze and cause cracks). I have no technical education, but sometimes I like to do something myself :)

@ stanislaw1954

In my area, I have already seen two cesspools that surfaced like submarines after completing a secret mission, so I do not have the courage to cover the tank with earth

stanislaw1954 wrote:

What is the purpose of this outdoor concreting? The soil around the reservoir is enough.

Maybe it's a good idea, I don't know what stiffness this tank has, but something like that (concreting) can protect this tank from being squeezed and tightened. If it happened that the reservoir is not "quite stiff" and just empty, especially when it is covered with gravel, and if it were after heavy rainfall, in spring, when the soil is "a little thinner". It also happened with a neighbor on the plots. He had a 1000-liter plastic tank buried for the "near-water cesspool". One spring it turned out that the soil around the tank collapsed and the tank "closed" inside. Concrete would protect the tank from something like this, because it is stiff.

It was only in subsequent posts that I found out that it was supposed to be a septic tank, which is sometimes emptied, so it is empty. In such a situation, it is probably better to concrete it, as the ground pressure may compress it, especially when it is empty.

stanislaw1954 wrote:

because the pressure of the ground can compress it, especially when it is empty.

And when the contents of the tank are pumped out / sucked under vacuum (septic tanker / cistern), this phenomenon is even more pronounced.

First, count how much concrete needs to be poured to load the tank, the base must also be reinforced and connected to the whole. Below is a photo of the concrete reservoir that came out.


2.5 m3 must be loaded with concrete weighing at least 2.5 tons.

wald3k wrote:

so I definitely have to weigh him down.

Pour the water, then pump it out Plastic (PVC) tanks called "Tuffi Tank" with a capacity of 5 m3 stand still without burying, and dug in without concreting is hoho. Want a photo?

nuszek wrote:

2.5 m3 must be loaded with concrete weighing at least 2.5 tons.

pour concrete inside the tank ?? I haven't laughed so much for a long time

Krzysztof Kamienski wrote:

pour concrete inside the tank ?? I haven't laughed so much for a long time

Read with understanding, or think logically, where it says inward, the diver also strains himself by pouring lead into the stomach - it would be funny only .

You think you want to cry - bury the tank and that's it. If it is poured with concrete, it will be difficult to remove it in the event of a breakdown (cracks.) Do you know how Old Indians do it here in the construction of home pools and ponds? And they have practice and experience in this. They make a trench a few dozen centimeters larger than the reservoir, they put gravel or rubble on the bottom of the trench and tamp it gently after settling empty tank.

@K-rzysztof Kamienski
Thanks for the idea. I'm sure the gravel / crushed stone idea is pretty good, but assuming it helps drain off the excess water. Unfortunately, in my case we are talking about a 12 meter layer of heavy clay. I drilled a well next to it and I know the cross-section of the layers well. This water will have no drainage. covering the sides of the tank with material other than concrete or clay (which, in turn, will not be thickened) can unfortunately create a 'bathtub' with water.

@ stanislaw1954
It will not be a septic tank, but a water tank from the well (I gave the septic tank only as an example). I drilled a well with a terrible capacity (500l per hour ..) and therefore I need an intermediate tank for watering the garden. This means that during the season the tank will be filled / emptied (although probably not to the bottom) at least once a day. The pressure of the ground also occurred to me. Thank you.

@nuszek
the tank is 2.5 m3 and I assume that there will always be at least 500l of water in it (for the health of the pump). I assume that m3 of concrete is about 2 tons, so together with some layer of soil it should eliminate the buoyancy. do I do well?

Anyone else have any idea? The hole for the tank is already being dug and I plan to finalize the assembly on Saturday.

wald3k wrote:

the tank is 2.5 m3 and I assume that there will always be at least 500l of water in it (for the health of the pump). I assume that m3 of concrete is about 2 tons, so together with some layer of soil it should eliminate the buoyancy. do I do well?

If it is not a flood plain, with water standing in the yard, pour concrete over the tank to create a shell / as you write for the future to strengthen the tank /. 3 m3 of concrete may be an exaggeration, but it will certainly go a long way.
ps. We installed a 10,000-liter fuel tank on a hill, where flooding with water is almost a miracle, but the UDT gentleman calculated the displacement of this tank exactly.

nuszek wrote:

wald3k wrote:

the tank is 2.5 m3 and I assume that there will always be at least 500l of water in it (for the health of the pump). I assume that m3 of concrete is about 2 tons, so together with some layer of soil it should eliminate the buoyancy. do I do well?

If it is not a flood plain, with water standing in the yard, pour concrete over the tank to create a shell / as you write for the future to strengthen the tank /. 3 m3 of concrete may be an exaggeration, but it will certainly go a long way.
ps. We installed a 10,000-liter fuel tank on a hill, where flooding with water is almost a miracle, but the UDT gentleman calculated the displacement of this tank exactly.

I don't mean 3 but 1 m3 of concrete. I assume that its mass is about 2 tons. 2m3 of water weigh the same (this is what I can pump out of the tank). I treat the top layer of soil as an additional reserve. I count it purely intuitively. Can anyone tell you how to correctly calculate displacement?

Kurtka na wacia wrote:

What is the depth of the water surface of the well and its distance from the reservoir? Perhaps it is enough to drain the tank properly and the drain from the drain will pour into the well. By default, I imagine that the highest water level in the well is lower than the level of the bottom of the reservoir. But if it is so, I do not know.

This is a deep drilled well. The static mirror is at the level of 11.5 meters, but this does not matter in this case, because pouring drainage water into this pipe is too high a risk (due to siltation). A large amount of water in the clay is very rare (early spring when the ground in the deeper layers is still frozen, thaws, etc.) but I have to somehow protect the tank against it.

Gentlemen, you also need to analyze whether concrete shrinkage will not do anything to the tank.

soniak2 wrote:

whether concrete shrinkage will do nothing to the tank.

While the concrete "solidifies", fill the tank with water "to the full" so that there is no "drop" of air and close it tightly.

wojtek1234321 wrote:

soniak2 wrote:

whether concrete shrinkage will do nothing to the tank.

While the concrete "solidifies", fill the tank with water "to the full" so that there is no "drop" of air and close it tightly.

Closing completely tight will be a problem, but the tank will of course be full. Will the use of dry / semi-dry concrete reduce the possible shrinkage effect? I know that such concrete will be a bit weaker but it is not a shelter after all.

wald3k wrote:

Is the use of dry / semi-dry concrete concrete

concrete B20 strong and slightly damp, easy to vibrate. Laminate does not age and in the 1st post you put it on well, and how did it go?

Put this well in such circles with a concrete lid and scream.

I live in cop too and I know what it is like. I have a water meter pit over 2 meters deep. When there is heavy rainfall, the water level reaches 0.5 meters ... but not from the bottom but from the top. The water will pass through all seals, the contractor also assured me that the well would be dry, after all, it was tarnished on all sides.
As for the load of your tank - 1 m? of concrete is enough, provided that it will press the tank downwards. The displacement of this tank is practically 2.5 tons, so 1m? should be enough. Of course, as you write reinforced concrete, the tank is always filled with a minimum of 500-1000 liters.