Thermostatic shower - very low hot water pressure and flow

30 Jan 2011
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United Kingdom
I have had a Mira Minilite EV thermostatic shower fitted as part of my central heating upgrade. The installation company have spent several weeks on site trying to figure out why the flow rate and water pressure on my shower is so low when I set it to hot.

They recommended and installed the shower. The boiler is a WB 30CDi combi.

I've even had my mains water pipe to the house upgraded at their request at a cost of £1,000.

The flow rate from all TAPS (kitchen, bathroom basin, bath and outside taps) is very good now - both hot and cold.

However, the shower is now extremely powerful on the cold setting but as soon as any hot water is mixed with the cold, the pressure and flow rate immediately halve (at least).

Any ideas what could be causing this? Could it be unequal hot and cold pressures? Shower not commissioned properly?
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Check the feed pipes where your Mira Minilite EV thermostatic shower connected. Check if the hot water feed pipe connected wrongly.
Turned out to be blocked filters in the valve unit. The central heating company failed to flush out the water pipes before installing the Mira Minilite shower. Instead, they advised I waste £1200 on a new mains water poly-pipe to increase flow rate, even after I told them that pressure and flow rates to my taps was fine.

Had to pay a plumber £120 to dismantle the shower, flush the pipes for 30 minutes each, pressure test, clean the filters and reassemble everything.

How could a fairly large central heating company with 100% feedback on MyBuilder fail to check the filters?
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Without knowing the before and after flow rates, I cannot guess at what benefit the upgraded water supply pipe gave.

Its a very basic ( but common ) failing not to flush out new pipework.

As a very minimum the firm should refund the £120 for fixing the problem they caused.

As for the upgraded supply, my feeling is that it will be of considerable benefit to you but they should nevertheless make a contribution towards it. Perhaps £300 ?

Please tell us what if anything you propose to do about this and feedback to MyBuilder.


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