Bob, the vent over the f & e tank is correct. It is the vent from heating system, it should not go to cold water storage tank as it will cause it to overflow to outside by pumping over and the water from heating will browning the clean water fit for washing yourself.
There should be no PTFE or plumbers mait, just the rubber sealing washer for large nut holding pump and boss white for 22mm nut holding valve.
By looking at the picture of pipework, the short pipe between 15mm cold feed and 22mm vent has been fur up narrowing the flow and the pump has been working hard pumping water and the only way the water is to go to vent pipe and pumping over into F & E tank and go through cold feed pipe back to same pipe to pump. I would try do the cleanser, if not working, I would cut out that tees piece and renew it.
There should be no PTFE or plumbers mait, just the rubber sealing washer for large nut holding pump and boss white for 22mm nut holding valve.
By looking at the picture of pipework, the short pipe between 15mm cold feed and 22mm vent has been fur up narrowing the flow and the pump has been working hard pumping water and the only way the water is to go to vent pipe and pumping over into F & E tank and go through cold feed pipe back to same pipe to pump. I would try do the cleanser, if not working, I would cut out that tees piece and renew it.
