Backyard Aquaponics
A place to discuss aquaponics

Does anyone know how to tell, or where to get information about the strength of in-ground concrete tanks?

I have a large 6000gal+ in-ground tank, at least 4 meters diameter, that I would love to build grow beds on, but am concerned about the strength of the tank taking all that weight.

It appears that some are built strong enough to allow vehicles to drive over them, but some are not. How do you tell which is which?

Myles.

It depends how it was designed and strength of reinforcing and concrete used to build it. If you know who built it originally you might be able to find out what it is rated for. Here in the states it has to be rated for H-20 (H-twenty) loading for a vehicle to drive over it. I'm sure you guys have some similar system.

How thick are the walls? How wide an area would you have to bridge with the growbeds? It might be feasible to build the growbeds so they dont press on the concrete at all.

Unfortunately that is what I don't know. Though back when it was built there may have only been a few suppliers - I'll look into that.



I'll measure the thickness tomorrow (bit late here now). From memory its about 8-10cm (3-4") thick on the top section.



I was hoping not to have to do too much form work, though I could place one end off the growbeds of the tank, effectively halving the weight, and perhaps lay a timber beam across the tank to take the weight (would be tipping over it all the time though...).

Myles, take some pictures of the tank please. You should use it as your fish tank

If you can dip test the depth that would help too!

My guess would be 4.0mtrs x 2.1 mtrs around 40KL...
If the wall thickness is a little more than 100mm and a sand backfill you will be safe if the tank is always full.
Bear in mind the top normally has a thickener or a taper for about 120mm
where the true wall thickness will be found.
As per Jaymie, photos will help!

Okay, here are the pics.

Dimensions:
OD: 4.3m ~ 14ft
Height: 1.8m ~ 6ft

By my calculations that's 5,000 Imperial Gal (22,730l)

The thickness of the top/roof of the tank at the opening is 95mm.

Don't worry Jaymie, I've been thinking about it

But I have some other options as well

...with a lid!
I don't expect it is ment to hold a car!
but neatly placed GBs (off) around the tank could save a pump.
I would suggest it does have a thickening, the taper is normally on the outside.
Sweet!!

seems like quite a few option too eh!

why aren't you filling it with rain water?

It is, well its about 3/4 full. Its our main house supply, with the large green one as a recent addition since we've expanded our gardens.

The concrete one was filling from the whole house roof, but is now on half, with the large green one on the other half. The green one overflows into the concrete one...which overflows down the drain

Initially I'm actually looking for a 2-5000 l tank, but if the world goes to the dogs, I recon I'll be swimming with the fish in the pool

The area around the concrete tank has been one of those dead spots that we've just not known what to do with - that's why I want to put growbeds there, with the 2-5000 l tank nearby.

sounds good to me!

Okay, I've found the answer to my original question, or near enough for me.

These guys - AllCast PreCast - have concrete tanks that come close to the specs of mine - 90mm lids, mine is 95mm - and a diameter of 3.5m, mine is 4.3m. They rate the lid load at 500kg.

I'm hoping to use a few 600l growbeds, so looks like I won't be putting them on the tank at all.

well found

An embarrassment of riches M! I would hurt someone to have those tanks just sitting around in the yard.