Re: hot water heaters
We usually manage to get air locks out by running for a time with the reservoir cap off. (not the overflow tank, but the pressure cap). Seems the air can 'find it's way out' that way. It does depend on the engine, and the exact part of the cooling cct that the HW tank was inserted into though. Theoretically the FWC pump should push/purge the air through and out..
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"