I just moved into an older home with baseboard hot water heat. When we moved in a month ago the relief valve was dripping slightly. One night it blew off and we could hear water running back in the tubes after the pump shut off. A day later that stopped and went back to its quiet running again. The water softener was not working, old model, and I replaced it with a new one, now the running water sound is back again and not going away. The relief valve is dripping more after the pump stops. What is going on and how do I fix it. The house is not cold, but the boiler cycles alot. Any suggestions?