Hi all, I recently had a shower fitted, not electric, the mixing bar
type, the plumber who fitted it only used a single pump, which was not
suitable because the cold water to the shower is mains fed and the
pressure of the cold water was stopping the hot water getting into the
mixing bar, to solve this problem instead of fitting a twin pump, he
fitted a water pressure reduction valve to the cold water feed to the
shower. The shower now works, but I noticed the warning pipe was
constanly dribbling water out. I checked the ball valve in the cold
water tank which seems to be working fine. But when the warning pipe
starts to vent water, the water level in the tank is above the
overflow, but the ball valve is shut. I can only presume the excess
water is coming from the vent pipe from the ho****er tank. Has anyone
got any idea why this is happening?

"Neil" wrote

Hi all, I recently had a shower fitted, not electric, the mixing bar
type, The shower now works, but I noticed the warning pipe was
constanly dribbling water out.

If I understand correctly, since the shower was fitted, water has been
overflowing from the main water storage tank in the loft.
You have tested the ball valve and are confident that this is not passing at
all.

If these assumptions are correct then I would suspect that the shower is
passing internally such that water on the cold side under mains pressure is
backfilling the storage tank via the hot supply pipe work.

Did the plumber fit isolation valves on hot and cold supplies so you could
isolate the shower?
How long does it take for the overflow situation to develop?

To check if it is the shower just:

Leave the system as it is and monitor the level in the storage tank (do not
draw off hot water, or cold water supplied from the storage tank during
monitoring period of course).
Decide how long it takes for the water level to rise a given distance.
Turn off hot and cold supplies to shower.
Draw off water from the storage tank to float valve set level.
Monitor the storage tank level over the relevant time period used above.

If there is no change in water level with the shower valved off, then it is
likely that the shower is at fault.

The only other explanation for this that I am aware of is a leaking coil in
the HW cylinder allowing central heating system primary circuit water into
the domestic water. This would normally be accompanied by dirty hot water.

HTH

Phil

Hi all, I recently had a shower fitted, not electric, the mixing bar
type, the plumber who fitted it only used a single pump, which was not
suitable because the cold water to the shower is mains fed

Can you confirm where the single impellor pump is?

Is it on the hot water supply line, or on the combined output from the
mixer?

The backfilling on the tank is because he forgot to install check valves on
the shower valve supply lines.

Christian.

Thanks for replying christian, the tank is back filling, the cold water
pipe supplying the Hot water tank felt warm and when I shone a torch
into the cold water tank i could see water flowing back in, if I
installed a check valve on this pipe would that stop the problem.