Just finished installing new Seaward 6-gallon. Also changed the hoses to and from engine (3gmf) while at it. After I reconnected everything, I started the pressure pump to fill the tank. Everything worked great except that I get this hissing sound as if there is air in the system. Only when turning on hot water faucet. When I shut the faucet, pump builds up pressure and then stops normally and hissing sounds stops. No such sound when runnning cold water. No leaks anywhere. I even let the pump run for 15 minutes with hot water faucet wide open and the hissing sound never stopped. No bubbles in the water and good pressure at the faucet. What do I do next ? Seaward's instruction talk about the possibility of hydrogen build-up ! If so, how do you get rid of it ? I want a boat, not a hot air ballon ! Anybody ever heard of this ?