Loud horn noise after unvented cylinder service

[Sard]

Hi all,

I've just had my unvented cylinder serviced and the expansion vessel repressurised (it had lost pressure completely) and I was getting a drip through the tundish. Now the cylinder/expansion vessel makes a really loud and unbearable noise (like a fog horn) everytime we turn the taps on.

Any ideas on what's causing this? I have contacted the plumber who did the service but wanted to get some advice on here too.

 

[Madrab]

It is usually down to the EV pre-charge pressure not being correct, does it stop after a bit when running the HW? Can aslo be an issue with the Pressure Reducing Valve, depends where it is vibrating

 

[Sard]

Sorry for the late reply, the noise stops after a while when the hot water is running. I'd say after 5-10 seconds. Shall I let some air out? Also the EV was taken off and the water was pumped out using a bike pump before it was repressurised if that helps?

 

[Johntheo5]

When the EV was removed and if it had been installed "upside" down with water end on top then the water should have just run out when inverted?.
The pre charge pressure should have been set (pumped) to the PRV pressure - 0.2bar, the PRV is normally set to 3bar so the precharge pressure should be 2.8bar.