Metro Vertical shower valve running cold

[Axel]

I have just got home from a frustrating investigation.

The original problem was a lack of temperature water in the basin tap. This was because there was debris in the check valves of the thermostatic shower valve and there was a back pressure onto the combi boiler. Also, the valve was connected the wrong way round (hot / cold) Now these two items are rectified,I find that the shower valve will turn off the hot flow in the 'cold' temperature setting, but mixes in too much cold with the hot at the hotter end of the scale, and so produces only a lukewarm shower. Ironically, when the valve was connected the wrong way round, it would at least provide hot and warm water, even if not thermostatically regulated, because it was shutting off the cold (instead of the hot) when in the cold water setting!

If I isolate the cold supply, only then do I get a hot shower (too hot, of course). Bathstore are sending a replacement cartridge, but were adamant that I would need to fit a Pressure Reducing Valve because the combi heated water pressure into the valve would be a little lower than the mains cold into the valve. I am sceptical of this, and Dan Robinson seems to think it is a flow restrictor, rather than a pressure reducer that I might need. I am confused. Any input out there?

It's a 'Metro Vertical Thermostatic Bath Shower Valve fed from a Potterton Performa HE 24.

 

[mega029]

Hi,

Did you ever manage to resolve your issue with the metro mixer?

I am experiencing a similar problem, had a 3 way metro mixer installed 20 mths ago. Worked fine for a couple of months but started to take around 10 mins before it reached desired temp and this slowly declined.
Spoke to bathstore who pointed me to Crosswater (the manufacturer) who asked me to check if cartridge was installed the right way and to flush it, this was to no avail and so sent me a replacement cartridge. This worked, however it still was taking a couple of mins to reach the set temp but I decided to make do with it as it was much better than 10-15 mins wait. But the problem has returned, called crosswater again and the technical advisor was suggesting that the boiler may not be providing equal pressures ( im assuming he was talking about the hot and cold feed) and this tap was a single flow system which some boilers dont like? The other (mixer) taps in the house work fine and provide hot water at excellent pressure and rate.
Any help would be grateful?

 

[Axel]

I fitted the replacement cartridge and it worked fine after that.

6 Months later it started having the same problem. I was busy at the time and the customer got another plumber in who rang me 'cos he didn't know what to do about it.

It could be that these cartridges are $h!te (fitted one more recently on another job and the new one had the same problem), or they are very fussy about pressure.

I think Screwfix sell an adjustable pressure reducing valve for £25, so if there's somewhere it can be fitted in line with the shower cold supply and still be adjusted, it might be worth a try.

http://www.plumbworld.co.uk/safeguard-pressure-reducing-343-21866

Crosswater stuff is usually good but I'm wary of the Metro shower valve!