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Connecting External Plastic Water Storage Tanks Answered

I would like to ask a couple of questions about joining two external water storage tanks.
The tanks have a capacity of 1,500 litres each and my plan is  to connect the two tanks with one inch pvc piping.
The domestic water inlet is low pressure (and that's being kind!) but tank A is usually full.
My question is will there be enough pressure in tank A to feed water through the one inch pvc piping and into tank B without using a pump?
If you consider the water pressure to be high enough to transfer water from one tank to the next, how many tanks could be connected in this way (I am thinking of four tanks)?
The outlet from the water pump feeds 9 washing machines in a small launderette. Sorry about the awful drawing.

Thanks for any advice in advance.


I have a very similar problem to this one, the difference being that both my tanks are filled from separate branches of the same supply using a ball valve in each tank to stop them filling. I then have an outlet from both tanks connected together that then goes off to a pump. One tank is 5000 litres and the other is 3000 litres, currently the larger of the two is redundant and its outlet valve is off, but come the summer i will need to introduce the second tank. I am located in southern Spain and in the summer they turn off the water supply to save water hence the tanks. My question is as the tanks are of a different size, if i were to fit the smaller tanks outlet with a non return valve so that the larger tank can not fill the smaller one via the outlet pipe, would this work i.e. would the joint outlet pipe still feed the pump correctly or would it have more or less pressure.

I appreciate that i could balance the two tanks, but i would much rather be able to use all the volume i can.

Many thanks.

There is an instructable that shows how to correctly connect two water barrels or tanks together.

If you want to fill B from A via a float-valve, as you have drawn, then B needs to be lower than A.

If, however, you connect A and B at the bottom, then the level In each will remain equal, at whatever height it happens to be, and when that level drops enough to trigger A's float-valve, both tanks will be filled together.

So that (second suggestion) would even work, if the float valves triggered the "stopping" of the tanks being filled any further, rather then "starting them being filled", right ?

It may be different in the US (I know toilet flushes are), but a UK float valve would turn on as the float dropped, and off as it rose.

If the water level dropped too far for the float to reach, the water would remain on.

Our toilet float valves operate as you describe, but I just meant that if one wanted the opposite "condition" (and it wouldn't be difficult to rig a switch that way) it would still work as far as I can see.

I think you just join all the tanks at the bottom, then they act like one big tank. Just run a pipe straight across at the bottom. Try it with plastic bottles.

+1 I'd vent each tank as well