bought this house the other day with a traditional Britannia St. James shower in it. Local plumber comes round and says: good thermostatic shower for a combi, how the hell did this work with a tank. British Gas plumber comes round and says: oh, not a good shower for a combi, only works with a tank.
How do I know which of the two is right. The one who is gets the job to fit a combi and some radiator changes, so it's kind of important to know whether the local plumber is reliable.
I don't know the shower type in question, but I've just fitted a thermostatic (bar) shower in my bathroom. Currently we have a tank fed system and it works just fine. A bit slow, but thats what the pump sitting in the airing cupboard is designed to solve when I plumb it in next week..
You might want to do a bit of research and see what the shower specs. are. Mine specified a minimum head for it to work properly - with our gravity fed system, we just about manage to meet the minimum (about 0.1 bar which is 1m)
The combi will be feeding mains pressure hot & cold into it, so knowing your local mains pressure & the combi flow rate might help.
The cynic in me says that BG just wants to sell you more (& cost you more for fitting :)
Gordon. I am just about to finish the installation of a bar thermostatic shower. Does the cold water connect to the inlet adjacent to the thermostatic control end or otherwise?
Basically, provided you are talking about a modern modulating combi with a high output and the shower flow rate is below the maximum that the combi can produce, you are likely to get good results with any thermostatic shower. Most problems concern hunting by the valve when changes in the hot water temperature due to flow rate changes occur. If you keep the shower well within the capacity of the boiler so that the output temperature doesn't drop, it will work perfectly. Also, a design that basically leaves the hot water alone and adjusts using the cold water will work effectively, even when the boiler is flat out.
If the shower doesn't have built in pressure equalisation, then you should consider fitting an external pressure equalisation valve.
However, if it was run off just gravity, then you are lucky to find any shower valve suitable, however much the manufacturers bleat about a 0.1bar minimum. You basically need mains or a pump to get a reasonable shower, as unless you live in a private water tower with the shower on the bottom, the pressure will be abysmal. With a bath, pressure is irrelevent, provided that it can provide enough flow. With a shower, flow isn't as important as the pressure to squeeze the water through the head with sufficient velocity.
Remember that I don't know the specific shower mixer, and there may be some specific design feature that makes it unsuitable for one type of water system or another.
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