Shower pressure limits

The installation instructions for my new (thermostatic) mixer shower specify:
Static pressure must be below 10 bar or seals may leak. Fit a reducer if supply pressure exceeds 5 bar running, apparently Must fit an expansion vessel on the cold supply if none in (combi) boiler.
How do I measure the running pressure? The only method I can think of is a manometer. Which would be pretty damn big, even if it had mercury in...
The diagram for my boiler (Glowworm 30ci plus) indicates a "domestic safety valve", and the max specced pressure is 10bar, so can I assume that it will vent water through the overflow if the pressure rises above that?
Ben
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wrote:

Plumber's merchants carry gauges for this.
.andy
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really want to.
However, 10 bar is pretty high, in fact 5 Bar is for many people. do you suspect esp. high pressure.
I just went ahead and installed mine (Mira Excel) Once installed it was ok, then a few months later - the summer it started to make a whistling noise - which was symptom of to high a pressure.
I fitted a pressure reducing valve and just fiddled with it until I though it was ok.
--
Chris French, Leeds

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10 bar would be extremely high and would only be rarely encountered in a UK mains supply (probably at the bottom of a steep hill with a water tower on the top). 10 bar is a common pressure limit for most domestic plumbing devices, not just shower valves. If it really does get close to this, you need a pressure reducing valve as the water enters the property.
Does your kitchen sink dent when you open the tap? As a gross simplification, a shower pump produces around 1-2 bar. (A gravity tank system produces around 0.1 - 0.5 bar).
Christian.
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My car tyres only take 3.1 bar, so I'd love a mains water system that lets me fill tyres with water to check for leaks. Ten bar would be ideal.
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