Hi all I had a thermal store fitted 18 months ago.(sacked original plumber and his so called expert as they had less of clue than me) finally up and running ok, now the oil boiler its connected to needs replacing (20years old) On checking the vent pipework on the top of the store it has a 22mm T, one end is open to the loft tank the other end i have traced back to the boiler flow pipe before the pump, is this correct as it seems to as soon as the boiler fires and the pump runs water will be sucked from both boiler and vent pipe, any ideas ? and one more thing is there any legal reason i cannot fit new boiler myself and have it profesionally checked and signed off, many thanks