Thermostatic Shower flow problem...

[construct]

Having just fitted an Aqualisa M100 Thermostatic shower to a gravity fed system, there seems to a water flow problem. When you run the shower at the lowest temperature setting (cold) the water gushes out with plenty of back pressure, but as soon as you increase the temperature, it becomes limp and weak. As you then decrease the temperature from hot to cold, there are fleeting surges in pressure only to return back to poor output.

Can anybody suggest what the problem might be?

Link to shower:
http://www.aqualisa.co.uk/Our-produ...and-easy-fit-bracket-High-Pressure/?area=3110

 

[Whitespirit66]

You missed the words 'Suitable for high pressure and combination boiler systems' in the product description.

Your system is neither of these.

Your only way out may be to pump the supplies to this shower. You could also take the shower back, and get one suitable for low pressure gravity systems.

 

[construct]

You could also take the shower back, and get one suitable for low pressure gravity systems.

That sounds feasible provided the connections are the same, I'll have to look into it with Aqualisa...

 

[Whitespirit66]

Before you look for another shower, you need to find out what pressure you have available.

Measure the height between the shower head and the surface of the water in the cold (largest) water tank in the loft. Each metre of head = one tenth of a bar pressure.

So for example, if the difference in height between tank water surface and shower head is 2 metres, this is equal to 0.2 bar.

You then need to look for a shower that has a minimum pressure requirement of 0.2 bar or below.