New Shower Flow Much Reduced

[JtB]

We've just had a new thermostatic shower supplied and fitted by a local company. We have a gravity fed system and our old thermostatic (Aqualisa) shower had an extremely good flow rate. We were informed in advance that the new shower would have a slightly reduced flow compared to our old shower due to new European regulations now applied to all thermostatic showers sold into the UK (intended to prevent scalding due to changes in water pressure). However, what we are experiencing is a very significant reduction in flow to the point that the new shower is virtually unusable. I believe the new shower is a Thermostatic Bar Valve (TMV2) shower (see photo below) and so I was wondering if anyone had any suggestions on what we can do. Is our only option to get a pump fitted? One thing I notice on the new shower is that there is only a quarter turn on the flow control (left hand knob) before it hits an end stop. There is also a button on the flow control and I would have thought that pressing this button (like pressing the button on the temperature control) would have allowed the flow control to be rotated further beyond a preset limit, however pressing this button does nothing at all. Any ideas what this button on the flow control is for and why a shower manufacturer would add a button that seemingly serves no purpose?

Any help or guidance much appreciated - many thanks.

 

[echoes]

Do you know the make and model of your new shower mixer?

Was the shower head changed at the same time as your mixer?

 

[JtB]

The supplier described it as a high performance thermostatic shower mixer supplied by Claygate. Looking at the Claygate website it looks very similar to the "Hudson Reed Minimalist Thermostatic Bar Valve LP2".

Yes, the shower head was changed too.

 

[echoes]

A possibility is that either your mixer, head, or both, are not suitable for the pressure you have. But the installer should have chosen accordingly.

I would check back with the supplier/installer to find out exactly what they installed, the minimum pressure recommended for the mixer and the shower head, and the actual head available (vertical distance from shower head to cold water tank). You get 0.1 bar for every metre.
Sorry not to be of more use here.

Another possibilty is muck in filters at the mixer inlets.

If you still have the old head & hose, see if that makes any difference.

 

[cozzmic]

Probably non return valves on the inlets and possibly on the outlet to the hose or in the hose itself. Mixer is probably only suitable for high pressure like combi boiler or unvented, not gravity. Aqualisa probably had the 22mm pipes going to it if it was an old model which would give a min of 2 gallons a minute with 600mm head (height above shower head to tank base) I seem to remember.