Sealed system, replace pressure gauge without draining down?

4 Jul 2011
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United Kingdom
Probably the stupidest question in a while so feel free to say so!

A freak accident in the garage (falling timber) knocked the front off the boiler pressure gauge (needle and plastic front and the spindle the needle fits to).

I have a replacement gauge and it is obviously a very simple job to unscrew one and screw in the new one. Except, of course the system is pressurised so if I don't drain down then high pressure water will squirt out, briefly.

Is it doable though? Anyone tried? I hate draining down and refilling and am trying to avoid it if this is doable.
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With a sealed system, you only need to drain about a gallon or two before there is no pressure left in the system. You could even open a bleed valve on a rad and let it run until it stops. Don’t forget to retighten the bleed screw. Then, change your gauge and repressurise the system. Job done.
Thanks guys. It is a WB Greenstar 24i and it does have a drain cock at the bottom of it (the only one I can find on the system so have used that to drain down before). I'll have a go at draining a bit out and see how much pressure there is when I unscrew the gauge.
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make sure you cover the electronics , you dont want water going in there

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