I am here because of viewing one of Shannons videos on youtube https://youtu.be/XFqPKvuk9A0
I was grateful to locate my boiler temperature relief valve. Nice job !
This house is a new build, 2012. So still under builders warranty too.
I have a constant running of cold water flowing through my overflow pipe. I live in England so its quite cold in winters and outside drops below freezing around this time of year. The water does lead outside, and I have noticed my cylinder/immersion tank making a lot of noise which keeps me up at night. I've had to turn the water off at nights, and gradually the amount of water running through the overflow pipe is increasing, last year around this time, I had it overflow from the pipe, so I want to avoid that as I just painted my downstairs ceiling

I've let some pressure off the release valve on the cylinder and the noise has quietened down a little but its still noticeable. I think the water in the overflow pipe has slowed down, but is still constant. I have contacted plumbers and heating engineers and just wanted to try some last efforts and educate myself before getting someone in.
I've included some photos. (Yeah not sure why they boarded in my cupboard)


and I wanted to know what the red pressure valve and the grey valve, on the right, with the lock on are all about? Seems that cold water passes through as the pipes are cold to the touch. All the water in the overflow is cold. Wondered is this going to be an issue? How much water should be running through the overflow pipe? (a trickle, a few drips, constant running water)