Query about indirect hot water storage tanks

I needed to fit a new immersion heater as the original 35 year old one had died a few years ago and I want to cut down on use of gas. The system is a Baxi gas boiler feeding the indirect hot tank via its internal heat exchange coil. Both the hot water tank and the heating system have their own cold water header cisterns in the attic.

I turned off the cold water feed to the hot tank and run all the hot taps until they ran dry. The cold water valve was VERY stiff to turn at first.

I then removed the immersion heater from the top of the tank and was surprised to find that the tank was filling slowly with water and started to overflow .. I could not get any further turn on the cold water feed valves so I had to work very quickly and get the new immerser in place.

All is working again OK but I am very concerned that the slow feed of water to the hot tank may be due to a leaking heat exchanger coil in the heating circuit.

Can anyone advise on this ? How could I investigate this possibility? I thought of putting some intense coloured dye in the heating header tank and seeing if the colour came through to the hot water taps circuit.

Any advise appreciated

IanR

Is the ball valve on then header tank for the cetral heating running when you have the supply to the DHW cylinder switched off and a hot tap open, or are you loosing pressure if its a sealed system. The dye thing does not really work as a collegue tried it and it gets diluted too much.

If your cold feed to the DHW cylinder is a gate valve (red circulare handle)then chances are its just passing slightly. a nip up with a spanner will solve this if future work is carried out.

superdupergasman said:

Is the ball valve on then header tank for the cetral heating running when you have the supply to the DHW cylinder switched off and a hot tap open, or are you loosing pressure if its a sealed system. The dye thing does not really work as a collegue tried it and it gets diluted too much.

If your cold feed to the DHW cylinder is a gate valve (red circulare handle)then chances are its just passing slightly. a nip up with a spanner will solve this if future work is carried out.

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This advice is very much appreciated and fully understood - I'll get my son to help me in the attic as I am an old dude and getting past going up there. The system is'nt pressurised.

I suspect it is as you suggest, a leaky cold water (gate) valve - it has only been moved a couple of times in 35 years - can't blame it for not waking up fully

Best regards

IanR

You might save on the gas but you'll have to use lectric instead - which will cost you about 3 times a much

Worth a bit of effort making sure the hot pipes are all insulated, and put another jacket, or old blankets/sleeping bag, over the HW cylinder. You can save a few quid a month doing that.

ChrisR said:

You might save on the gas but you'll have to use lectric instead - which will cost you about 3 times a much

Worth a bit of effort making sure the hot pipes are all insulated, and put another jacket, or old blankets/sleeping bag, over the HW cylinder. You can save a few quid a month doing that.

Click to expand...

Yeah Chris - either way its not cheap. I really only wanted to have the option of other hot water as my old heating system may have old age problems like myself. The immerser has been duff for about 5 years.