I have a megaflo unvented cylinder on the first floor of my property and I am trying to recharge the air gap. I have turned off the incoming cold mains valve upstream (and right next to) the pressure regulating valve and then opened the hot water taps at the lowest point in the house. The problem I am getting is that I have had the water running out of these taps for at least 10 minutes with some really loud gurgling noises from the tank while the water is running. The hot water tap flow reduced significantly and did actually stop for around 10 seconds thinking it had worked (so I can then turn the TRV valve on the side of the tank to recharge the air gap), but it suddenly started to emit more water and again didn't stop.
I did think it could be the mains supply valve right next to the PRV that is faulty but even when I turn off the whole mains water the same issue occurs. My upstairs cold is also tapped downstream of the PRV as I was thinking there could be an issue where the cold supply is flowing back around the mixer valves in the bathrooms, but since the feed is downstream of the PRV and mains shut off this shouldn't be an issue? The only other tap that could be causing the issue is the kitchen as that is fed from the mains supply, i.e. upstream of the PRV for the hot water cylinder?
I did think it could be the mains supply valve right next to the PRV that is faulty but even when I turn off the whole mains water the same issue occurs. My upstairs cold is also tapped downstream of the PRV as I was thinking there could be an issue where the cold supply is flowing back around the mixer valves in the bathrooms, but since the feed is downstream of the PRV and mains shut off this shouldn't be an issue? The only other tap that could be causing the issue is the kitchen as that is fed from the mains supply, i.e. upstream of the PRV for the hot water cylinder?