Water level in feed and expansion tank

[arni]

Hi, I read in an earlier post that the water level in the tank should be 10 cm and that the ball valve should be adjusted to cut off the flow at this level. Can someone tell me why the tank only needs this level which seems quite low compared to the size/height of the tank. What happens if it is much higher, as it appears to be in my tank.

I am trying to decide whether I have a leak in the system, hopefully in the HW tank coil (as I have solid floors) and having tied up the ball valve arm the level did go down to about 10cm over about 24 hours, at which point I panicked and filled it back up higher. Is there a way of checking whether the coil is at fault?

Any help will be very much appreciated

Arni

 

[kevplumb]

the water needs somwhere to expand to by approx 20% volume

 

[Bahco]

The tank feeding your hot supply can be as high as 2 ins below your overflow pipe, but the smaller tank feeding your CH should be set at 100 mm cold.
TO check your coil, tie up your CH ball valve and see if it empties completely. If it is leaking , this water will find its way back up to your other tank and out through the overflow

 

[Slugbabydotcom]

Can someone tell me why the tank only needs this level which seems quite low compared to the size/height of the tank. What happens if it is much higher, as it appears to be in my tank.

Water increases by up to 1/20 extra volume when heated so if you have 20 gallons in your system the other gallon 'created' needs somewhere to go hence the term expansion tank as the water 'expands into the space above the 4" level. A larger system needs a larger expansion tank.