/ Replacing a Shower Thermostat

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FesteringSore - on 30 Nov 2016

Just about to replace the thermostat on our Mira Coda shower. Looking at the handbook it looks to me that I do not need to isolate the water supply. Anyone got any expert knowledge please? I'm not sure if there is a separate isolator valve for the shower(ie between the boiler and the shower)
Post edited at 16:04
Thugitty Jugitty on 30 Nov 2016
In reply to FesteringSore:

That looks like a thermostatic mixer, with the flow and the temperature all controlled in the same unit. I forgot to isolate the hot and cold supplies when changing the thermostat on a similar unit once, and I got very wet. Surprisingly difficult to push the thermostat in against the torrent of water, even with just the pressure from a header tank. Mine had isolation valves just before the pump (which I had remembered to switch off).
jkarran - on 30 Nov 2016
In reply to FesteringSore:

The shower/bath flow control valves are on the outlet of my thermostatic mixer, if I unscrewed the mixer unit without isolating the supplies I'm pretty sure I'd get drenched.
jk
FesteringSore - on 30 Nov 2016
In reply to both: Thanks. I can't remember if the plumber put an isolator valve in for the shower. Can't see one anywhere although I presume there would be one in the boiler(somewhere)

deepsoup - on 30 Nov 2016
In reply to FesteringSore:

'In' the boiler?? No, don't go inside.

Is it a combi boiler? If the boiler feeds hot water to the shower and there's no way to isolate between the two, you'll need to turn the boiler off then turn off the cold water feed into the boiler. No water in = no water out.
Neil Williams - on 30 Nov 2016
In reply to deepsoup:
Also opening your taps downstairs, if you have to turn the water off for the whole house, will drain the system down so there's less stuck above it. Though depending on the pipe run there will still be some.

If it's tank-fed you may have to drain the tank down if there's no stop-tap on the tank - to do that open any tap below the shower that's connected to the tank (i.e. not the kitchen cold).
Post edited at 17:50
marsbar - on 30 Nov 2016
In reply to FesteringSore:

Do not open up the boiler case.
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balmybaldwin - on 30 Nov 2016
In reply to deepsoup:

> No water in = no water out.

Most of the time (or at least limited mount of water out)

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