This doesn't make sense?

[6397Luke]

Can anyone help? A friend of mine has 2 CWSC in her loft. The two are linked by a 22mm pipe near the bottom of the tanks and both have independent float valves.

I'm told that the second tank was fitted to enable the installation of a shower pump?

Anyway, only 1 tank has an overflow which now continuously pours out water. I've replaced both float valves but this hasn't solved it but when I isolate the feed to the tank with no overflow, the second tank stops overflowing.

This tells me that one tank is casuing the other to overfill, however replacing the float valves hasn't sorted it and I can't understand why or how to solve it?

Any ideas will be greatly appreciated?????

Thanks.

 

[JCplumb]

Because they're linked the water level will settle at the same height (above sea level - not above cistern bottom level) so one overflow must be lower than the fill level of the other tank.
Reduce fill level by lowering the ball on the float valve arm on the one with the higher fill level, or increase overflow height on the other one.

 

[jaydebruyne]

Just out of curiosity, is this a new install of the 2nd cistern?

 

[lame plumber]

only need one filling valve if its been installed correctly with take offs in other cistern,

 

[Ray Stafford]

only need one filling valve if its been installed correctly with take offs in other cistern,

If they are relatively small tanks (say 2 x 25ltr) on a 15mm feed and HP ballvalves (with their tiny apertures), its worth putting a valve in each - it substantially reduces the chances of a long shower draining the storage.

 

[jaydebruyne]

As per water regs, you also need an overflow in every cistern that has a float valve. But as above, if it's only two cisterns only one float valve needed. I also thought you had to have two link-pipes, one at the bottom and one in the middle of the cisterns to promote water circulation..