Header tank for central heating over flow pipe to out side hot water being released. Hot water coming from Swan neck piper from hot water tank in airing cupboard, this pipe only releases hot water when central heating comes on to heat rads and hot water to taps.
No discoloured water coming out of hot water taps, Ballcock in tank ok and floats ok. Drained central heating system and refreshed still have same problem, not sure where to look next before I call in professional help.
Any ides would be appreciated, many thanks