Unvented heating system losing pressure

[Kevine]

Hello
I have a closed unvented heating system that loses pressure very regularly. I am having to top-up the system via the filling loop every 2 to 3 days to 1 bar, then it's down to zero when I top-up again.

The tundish on my system was discharging recently and a pressure valve was replaced, this stopped the water discharging but system still loses pressure. I don't believe I have a leak, no visible damp patches anywhere.
My pressure vessel hasn't had any checks.

Is there anything further I can check or should I at this stage get the system fully checked out.

What should the engineer be checking as next steps?

Anything further I can check on the system?

Any other suggestions welcomed.

Many thanks
Kevin

 

[oldbuffer]

1. What is losing pressure, the sealed central heating system or the unvented hot water system or both?
2. Is the tun dish on an unvented hot water cylinder, or on the pressure relief pipework from a system or combi boiler?
3. Some photographs might make remote diagnosis somewhat easier.

 

[Kevine]

1. What is losing pressure, the sealed central heating system or the unvented hot water system or both?
Both. My understanding they were one system
2. Is the tun dish on an unvented hot water cylinder, or on the pressure relief pipework from a system or combi boiler?
On a unvented hot water cylinder
3. Some photographs might make remote diagnosis somewhat easier.

Will send some. Thanks

 

[Kevine]

Adding some pictures