Hot to cold shower off combi

Mr_da

Hi can anyone give me any ideas, I’ve got a mixer shower run off a Worcester combi boiler . And it goes from normal to very hot then cold . I’ve had a Worcester engineer out who’s run test on the boiler and it works great on every other tap, but the flow to shower drops below what will continually keep the boiler running.
I’m not sure but would it help if I tried changing any valve or anything on the shower end. As at least now have narrowed it down to the shower.

nofoollikeold

1. Is the shower piped correctly? Normally hot goes in on left, cold on right.
2. Does the shower have non-return valves, either built in to the shower or fitted separately to hot and cold supplies.
3. What type of shower is it? Bar mixer, exposed mixer, concealed mixer? Thermostatically controlled?

Photograph of shower might help.

Mr_da

It’s a concealed mixer , don’t know the make , think it is piped in correctly as shower has worked well in the past , just getting gradually worse, I.e hot to cold

Norman_Castle

it works great on every other tap, but the flow to shower drops below what will continually keep the boiler running.

Some shower heads restrict the flow to save water. Adjusting the spray pattern might help. If the problem is getting worse the shower head might be getting blocked with limescale.

Mr_da

Thanks for the reply’s, don’t think it’s the shower head as it’s the same if the water comes out of either the water fall part of shower or out of the standard head in the end of the pipe. I’ve been trying to remove the thermostatic valve but it won’t budge. Not sur how to upload a picture of the shower

Mr_da

Just in case anybody ever Google’s this, it was the thermostatic valve, took the gamble changed that and works great