its sounds as if your water is to low. when this happens the pump cant create enough pressure to disolve the tablets. also it doesnt heat the water because its not reaching the heater. this will make it not desolve also. your water inlet valve needs to be replaced. this lets water in on a timed cycle. if its not opening fully theres not enough water going in . the timer only allows so much time to fill then shuts the valve off. replace the valve and you should be all set.