Our heater was making loud banging noises and shutting down, so we replaced the thermostat hoping that would solve the problem. Unfortunately, when we took the heater pipes out to replace the part the pressure release valve fell down into the pipes and we were unable to retrieve it. We are now running it without it, and it seems to work fine, but we are wondering if this is a problem. Can we safely run it without the valve, or should be replace it right away? What does that part do?