Water leaking through tundish

[alwaysproblems]

From the t&p valve, does the valve potentially just need refitting?

 

[Madrab]

That's possibly down to the cdylider pressure running up but easily sorted. TBH though if your UV chap was in and didn't spot that and the rust mark then I have to be frank, he shouldn't be working on the cylinder.

 

[alwaysproblems]

Tbf there was only a dry stain but since his visit appears to be leaking now. As you said probably down to pressure. I've noticed a slight increase especially when I first turn on the hw tap.

As I said I'm limited in choice here, there are only 2 plumbers in the area and one wouldn't respond so it is what it is. He seemed familiar with the system. I had plumber's out to my old.place where they didn't even know how to take the cover off a combi boiler.

With this being oil and unvented its all new to me.

 

[Johntheo5]

The cold water mains pressure to my house is in excess of 7.5bar with no prv.l except the one on the boiler set at 6bar I think. Is this the likely cause of the leak?

There is another possibility, there is no PRV on the 7.5bar cold and you havn't got a balanced cold off your cylinder PRV so perhaps the high pressure cold is leaking across a mixer valve and pressurizing the cylinder back through its hot outlet?, you may be able to isolate the cold mains at the cylinder, open a hot tap and see does it continue to even dribble out and probably cold?.
Also the PRV (pressure reducing valve) at the cylinder should be 3.0 Bar.

 

[Madrab]

What make is the cylinder and can you post a couple of pics of the setup and the big combination valve that supplies the cylinder?

Tbf there was only a dry stain

Any stain anywhere on a tapping would warrant further investigation. Unvented cylinders need serviced yearly as they do have the potential to be dangerous if the safety systems failed and the pressure ever built to excess.