Unvented water system - hot pressure variable

[pbutterworth]

Hi,

I've got an Ariston unvented waterstorage sylinder, attached to a Worcester-Bosch gas boiler.

Recently the hot water has been playing up, but I cant understand why. The boiler is firing up and heating the tank as expected, and sometimes the hot water comes out fine, other times it goes cold after a short time. It's especially bad in a loft shower room.

Any ideas?

Thanks
Paul

 

[twgas]

Could be unbalanced supplies, you need a suitably qualified engineer to service an unvented.
Is it only the shower that has a problem?

 

[powell30]

Agreed. Has a balanced cold been taken off the system AFTER the combination valve? If not it might be causubg you issues.....plus the shower mixer may be fault and the cartridge needs reapir/replacement

 

[pbutterworth]

Thanks for your responses. It's worst at that shower, but unreliable everywhere. I just gave the kids a bath, and we have a thermostatic mixer tap, pretty much as soon as I turned the tap off, the hot feed felt freezing.

Is that consistent with an unbalanced system?

I will get someone in, but prefer to have some ideas first.

Not sure whether it's related, but there is a slight hissing at that tap occasionally also, could that be the cause?

Thanks

Paul

 

[powell30]

It's possible you have a mixer tap letting the cold by if the system is not balanced on both sides. Has a check valve been fitted on all hot outlets or just on the hot out the tank? Finally it could be faulty mixers but i can't see all of em going faulty at once so my guess is non balanced with a mixer tap letting cold by

 

[pbutterworth]

Thanks for your feedback.

I prefer to have views from someone else when I call in an engineer.

I guess it could be a dirty filter, or because the cold feed isn't taken from after the pressure reducer.

Does anyone have any suggestions of reputable engineers for unvented systems in SE London?

Thanks
Paul