shower problems

[Dr DIY]

Hi all, hope you can sort my problem out.

I had a worcester Bosch condensing boiler fitted earlier in the year but ever since then we have been having problems with the shower. The shower has recently been replaced with a thermostatic shower and will run ok for a few minutes and then all of a sudden it will go freezing cold. The hot and cold supply, before they reach the shower supply a vanity basin in the loft and I believe the hot supply to the basin has been fitted with a thermostatic mixing valve to prevent scalding in the shower if all the cold water flow was to be used.

shower fitted is this one..... anybody think this mixing valve is causing the problems or is it the boiler.

Many thanks

[calums]

The plumbing sounds a bit confused in your setup. The mixing valve for the vanity should be fitted after it is tee'd off ie should be independant of the rest of the house plumbing. The only purpose for fitting such a valve is for the basin that its feeding so that kids don't scald their hands. If as it sounds, your mixer is also feeding the hot water supply to your shower then you will never get good performance. It is however difficult to say whether this is causing the cold problem, but I can say that it is plumbed wrongly by your description. Also a worcester combi has a control for water temp. So you can avoid scalding hot water by adjusting it at that end. This also has the effect of increasing the flow rate of hot water to all taps. Adjust the dial so that you get water at the correct temp for doing dishes in without the need to add cold water. Calum