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Married sons shower not working. Thought I would treat them to a new one. The house has a combi boiler. (with back up cistern & hot water tank,immersion heater). IS THIS POSSIBLE.
Went up to house to see what I would need to buy. Thats when my problems started. Inside the front cover of the shower unit it says power shower. I know you can't run a power shower from a combi boiler. There appears to be only a cold water connection to the shower unit coming from the cistern in the loft, again does not suggest a power shower. Electric cable to the unit is definately not 6 or 10mm so does not suggest an electric shower.
Can U help a puzzled DIYer

is it a power shower running from the tank rather than the Combi?

This is a guess based on what happened to my parents. They had a power shower and the council care and repair suggested they had a new central heating boiler. Sitting in on the meeting I pointed out the power shower and expected a open vented system to be fitted and the cistern to be retained.

However it transpired the grant for central heating up-grade had nothing to do with care and repair they had only passed on information and when the boiler arrived it was a closed vented combi boiler with instant hot water. I pointed out the error and was assured the info had been passed on to installing firm who would send a second team to correct shower problem.

However it seemed there were crossed wires and the foreman when he arrived tried to tell me that tough an electric shower would now be needed. I was able to point out that this was not an option due to size of supply to house and that by leaving old shower connected they had broken the law.

After a lot of discussion he agreed if we provided the materials they would change power shower for a mixer valve. This was done.

However had I not known what was possible and the law I am sure my parents would have been left without a functioning wet room.

However the mixer valve does work well. In fact very little difference between old and new system. Because with most combi boilers the hot water is at cold water pressure a mixer valve gives one a shower at cold water pressure.

I theory the old power shower with no power to it should have worked. In practice it was not able to regulate the water well enough.

I would guess when boiler fitted some of the pipework to shower has been removed as power showers do have both hot and cold supplies. However because it runs on mains pressure 15mm pipework is not required and by using plastic pipes it is nearly as easy to supply water as to fit new cables. Although some insurance companies will not allow plastic. Seems many houses have had plastic pipes fitted and the inserts have been missing and locks have not be screwed up plus mixture of makes of pipe and fittings has also caused problems.

But parents, myself, and daughter all have mixer valves and no way would I ever fit an electric shower. Son has power shower but that has to be powered as he lives on narrow boat.

How does this seem to match to what your son has?

Yes. Was up at the weekend and had another look. It is a power shower with the cold supply coming from the water tank and the hot coming from first draw off on the hot water tank (no isolation valve). Electrics coming from a fused spur located in the attic. When I had first looked inside the shower unit I couldn't see the hot supply, it is hidden by the outlet hose going to the shower head. Just need to find a suitable replacement now and get the job done. Thanks.