Mystery Tank: please help identify!!

gofasterdad

Hi,

Can anyone tell me what the small tank on the top left corner of the picture is for?

I think it is always empty as it seems as light as a feather. I think it might be some sort of overflow tank, but I really don't know.

dathi

its the expansion tank it has a rubber membrane in it with air on one side and the water on the other. as your water heats up it expands, and the water expands into the tank by compressing the air

gofasterdad

Thanks dathi. I was having a look around because the water pump keeps switching on and off during the night (around about the same time that the gas boiler switches on to heat the water).

I'm obviously not a plumber, but I like to have some idea of what's going on.

Calahonda52

dathi wrote: »

its the expansion tank it has a rubber membrane in it with air on one side and the water on the other. as your water heats up it expands, and the water expands into the tank by compressing the air

dathi: does this tank play any part in reducing the cycling of the pump in a pumped system[ie is it solely hot water expansion related]: e.g. pump on cold water from attic tank which then pressurises hot and cold.

Thanks.
C52

K.Flyer

The vessel in the O.P.'s picture is primarily for expansion of the hot water in the cylinder as its a sealed system.
Constant short cycling of water pressure boosting pumps tends to be as a result water loss somewhere. This can then be exaggerated by a faulty vessel as there is no reservoir to draw down the pressure from, so the slightest loss of water can cause the short cycling effect.

Calahonda52

Thanks, K, that explains it.