Testing hot water pressure

[Reshweb]

If I check the pressure at a shower outlet on an unvented system should I see the value as set by the PRV (3 bar) on the cold water inlet group set or will the reduced pipe size to the shower head change the pressure ?
Other than removing the expansion vessel connection there is no other way to easily take a reading near the valve set.
Graham

 

[Chuck]

If I check the pressure at a shower outlet on an unvented system should I see the value as set by the PRV (3 bar) on the cold water inlet group set or will the reduced pipe size to the shower head change the pressure ?

As long as there is no flow and the the shower outlet is at the same height as the PRV the diameter of the pipe linking the two won't affect your measurement of pressure.

The pressure you measure may be a bit higher than the PRV set-point because of the way expansion vessels work but if you draw a small amount of hot from a tap, just enough for the PRV to start passing to refill, the measurement should be okay.

Measuring the pressure at an outlet is okay but please remember, however, that any changes or adjustments to an unvented hot water system need to be made by a professional plumber qualified to work on unvented systems. This is often referred to as 'having a G3 ticket'. Do not mess with the expansion vessel connection, or any other parts, yourself.