System Boiler & MagnaClean Queries

[RVS6]

Hi
Quick question. I have a system boiler (Worcester Bosch). There is a Magnaclean filter fitted, which I assumed was just on the central heating. Heating was turned on a couple of days ago and the pressure on the boiler has been dropping. Last night I made sure the heating side was turned off, wrapped kitchen roll around all rad valves p/w at each rad end, around p/w below boiler and around magnaclean, re-pressurised to 1 bar and left it until this evening. Pressure has dropped by somewhere between 1/3 and 1/2 bar. Heating definitely hasn't been on. Hot water did come a bit earlier for an hour or so. I did notice the magnaclean was hot (it is located immediately below the boiler).

First question - should the magnaclean get hot when just the hot water is on? I thought the m/c was just attached to the central heating side. Can the HW side mix with the CH side e.g. if the diverter valve is faulty?

Second question - if there are no sign off leaks anywhere on the central heating, what can cause the pressure to drop, especially when the heating hasn't been on? Could it be something to do with the expansion vessel?

I'd appreciate any thoughts.

Many thanks.

RVS6

 

[kidgreen61]

Your boiler heats the water in your HW cylinder through a coil, the water going through the boiler is separated from your domestic HW.
If the boiler is on for HW then the Magnaclean will be warm as water is flowing through it from the return pipework from the cylinder.

The cause of the drop in pressure needs careful investigation, you may not have a leak, it may be from the pressure relief valve, that PRV may be letting water by because it is faulty, or because your expansion vessel is flat.

Or, you may have a small leak where you can't see.

 

[RVS6]

Thanks for the quick response.
There is no water coming out of the pressure relief valve outside, bone dry.
Previously I recall a similar issue and I think it was due to the pressure vessel, needed pumping up? Does that make sense, i.e. can an issue with the pressure vessel cause a loss in pressure? When the heating does get put on the pressure doesn't shoot up.