I just pull the cold water line off the water heater and using a 3/8" hose mender I put it into the line leaving the hot water tank. That bypasses the heater.

However, I'm pretty sure that opening the drain valve will not get all the water out of the hot water tank. When I took my old tank out last fall to put a new one in, water came out of the drain valve even after I had let it drain overnight. A fair bit of water. Our old water heater got decrepit but didn't burst from ice, so I'm not sure what to make of that water still being in there.

Your idea sounds right though, I think you would need 3 valves and some tube.

Did the by pass thing last year after having the original gate valve system fail and cause overheating... I fastened the ball valves to some starboard material and hinged it so I could get underneath it to access the packing box and other things in the quarter berth. Flow direction and hoses are marked. To bypass the Water heater turn all valves 90 degrees. Attached is the best photo I have. It is still raining in eastern canada and there is no inspiration to go out to the boat and get ready for launch in two weeks..... three weeks late.:(

[QUOTE=raymond kalinsky;22354]Hi Has any one put a bypass on the hot water heater. I have to un hook the tubings to run anti freeze into my hoses and tanks. on my travil trailer I have a tube to stick into the gal jug of anti freeze and turn a valve to suck it up into all tubings and tanks. this by passes the hot water heater, and takes a matter of minutes.Any suggestions whould be help full. I figure I need 3 valves one in the intake tube to divert the anti freeze around the heater ond on the out side to prevent back inflow and one in the mittle to shut off the by pass.
ray Kalinsky, Little Miss Magic[/QUOTE]

I installed this gizmo last fall to address this very issue: a Camco 35983 Quick Turn Permanent By-Pass Kit ( [url]http://www.amazon.com/Camco-35983-Quick-Permanent-By-Pass/dp/B0006JJ57Y[... ). It uses a diverter tee valve and a backflow preventer, rather than the 3 valves you were thinking of. There are a number of similar kits on the market (you could put something together with some valves and tees, but this was fairly compact).

I do the same as Bud.   For a once a year bypass it is not much work and is cheap and fast.   Having valves in place for a permanent solution is certainly more elegant, but I'm not sure it is worth my while.

Sounds like a useful mod to the system for sure.