back filling tank

[Macplumbing]

. i have posted this item elsewhere on this forum but a customer of mine is having problems. the cold water tank is overflowing. after changing ball valve i was called back as tank was overflowing again. cold water tank is back filling from cold feed to hot cylinder. house has three mixer taps and i was going to put check valves on hot side of each tap. problem is bath tap is hard to get at and will mean removing toilet and basin. is it ok to put a check valve on cold feed to hot cylinder rather than individual ones on taps or is this a no-no?
cheers
mark

 

[Agile]

Its not clear to me exactly what you have decided the fault is.

Since the cold cistern usually supplies the hot and cold taps I am not convinced you hve correctly diagnosed the problem.

It would normally be a mains cold supply feeding back either through an unvented cylinder or from the heating system.

Tony

 

[giblets]

Are the mixer taps served by mains water on the cold side?

Is the heating feed tank higher than the main cold water tank?

 

[mehran]

agile i understood what he was saying. been to a job last month where the hot water was feed from a vented hot water tank and the cold from mains. the kitchen mixer tap was letting cold water be pushed in the hot water side and overflowing. in any case the heating was knacked so we fitted a combi and placed a check valve on the hot water side of the mixer tap as she did not want a new tap.

 

[Macplumbing]

3 mixers are served by mains pressure cold and vented hot. bases of cold and f&e tanks are level. cold tank only supplies hot cylinder.
cheers

 

[Paul Barker]

If there is an indirect cylinder check if the water in the header tank is hot when the heating is on, if so, new cylinder.

If cold, then you should deal with the mixer which is causing the problem.

This occurs with combis also, I find that if you walk round the house looking closely at all mono taps and showers you can actually hear the one causing the back flow of water. That is the one you need to deal with. Unfortunately it probably will be the one most difficult to do.

I don't think a check valve on the cold feed to the dhw cylinder is the best way of going about this. For one thing the culprit will continue to cause dilution of your hot water at all other outlets so hot water performance will be very poor. For another the check valve will impede flow of an already low pressure system.

 

[Macplumbing]

thanks for all the advice, much appreciated.
mark