A couple of days ago, my central heating and boiler works perfectly. My husband yesterday have to turned off the water pipes to the hot water tank in order to cahnge a cartridge in the shower vale. When we turned back the water pipes to the hot water tanks, the central heating pipe was hot and so is the radiator but the hot water is just about warm. Is there something wrong with my boiler or the hot water tank. radiator working perfectly. hot water working but only warmed no matter ho much I turned up the temperature. Please help.