Had to turn hot water off because of a leak so opened up the hot taps and drained the tank , sortedf leak filled tank bk up but it will only fill half a bowl of water, then stops header tank is working and fine , un did the valve and water came out seeming to say the tank was full but when u run the hot tap the water only comes out enough to fill a washing up bowl half way then stops as to say no water left cold taps all fine