I've got a conventional vented pumped c/h & hot water system. Just after the pump there's a 13mm pipe coming out of the 22mm pipe and it goes to the return side of the system back towards the boiler, there's a gate valve in the way which was partially open when we moved into the house. Does anyone know what it's for cos if the gate valve's open it allows heated water to return directly to the boiler again and I can't see why.
TIA
Andy R