Combi boiler pressure drops when turn on hot water tap

[MattyMatt84]

I have a Worcester Bosch Greenstar 25 combi boiler which was fitted 2 months ago. It also has the filter fitted.
The pressure on the boiler is set to about 1.3.

When I turn on the hot tap (tried all 3 in the small house) the pressure gauge on the boiler drops to just under 1. The hot water still works though and when the tap is turned off the pressure gauge on the boiler soon goes back to the normal level.

When it fires up for the central heating it's fine though.

Any idea if this is an issue or just me worrying over nothing?

The only thing changed in the last week is the radiators bleeding and the boiler then topped up a little bit.

 

[muggles]

It's just the effect of the pump kicking in

 

[chrisw99]

Mine (not a Worcester) does exactly the same, and I think it's down to the following...

Your system water is normally in the loop 3-4-5-6 in the above diagram, and the pressure gauge is telling you the static pressure of the water in that closed loop.

When you turn on the hot water tap, the diverter valve at 8 draws the system water into the secondary heat exchanger 9. This causes the pressure in the main loop to go down as the water is spread out a little bit further through the pipework 11.

 

[ianmcd]

nothing to worry about its normal just as already advised the pump is cutting in.