# How to calculate outward pressure of water tank with salt in it?

I'm building a flotation tank.

To make the frame, I'm thinking of just using wood (10 cm by 10 cm treated pine). like in the design attached. And connecting the pieces of wood with metal brackets and screws.

I have calculated the volume in litres = 1,728 Lt Also, the water is heavily mixed with Epsom salts = 500 kg

So my question, please...

if I make the frame with wood and use some steel wires to hold it around, would that be strong enough to keep the water and floater?

like 2 wires at 20 cm and 40 cm from the ground, tensile strength 2447Kg

So 2 wires will be enough to contain the water, salt and floater?

how to calculate tensile strength on the wire cables?

## 1 Answer

The answer below is only an estimate and is not guaranteed to be correct, so make the tank stronger if there are any doubts!

The pressure at a depth of 60cm is $$h \rho g$$ where $$\rho$$ is the density

With the salt and in case the salt sinks, the density might be as high as 1500kg per cubic meter.

So the maximum pressure is about $$P = 9000$$ Pa

The expanding force on the biggest side is $$2 \times P \times 0.3 \times 2.4 = 13, 000$$ N

The area held by the bottom two wires being taken as $$0.3 \times 2.4$$

That is, a tension in the bottom two wires, (the ones along the 1.2m side) of $$6500$$ N each.

Then tensile strength of the wires is about $$2450 \times 9.8$$ N = $$24,000$$ N - so they should be strong enough, although it's getting quite close for comfort, so perhaps a couple more wires, spacing them so they are closer together at the bottom, where the pressure is greatest, might be best.

All the best with it.