I think John is on track. When you got only cold water, that probably is because the water heater is being bypassed, causing the incoming cold water to be diverted to the outgoing line.
When you reversed the bypass, hot water should come out of the heater and flow to the faucets. The only think I know of that would stop the flow is a defective checkvalve. It is screwed into the water heater and the outgoing line screws into it. We had this happen once. A dealer (any brand) will have one. It was around five bucks a couple of years ago.
If you get air hissing when you open a faucet, then the checkvalve is ok and the water heater is pushing out the air as it fills with water, as John said.
Your water heater is probably a Suburban. The dealer may need to know that to get you the right checkvalve.
|