Water heater replacement with coolant lines...

Go to Home Depot and pick up barbed by thread adaptor and cap. Pull hose off heater and shove in hose. Should loose next to nothing. I think mine is 3/4 inch or maybe 1inch.

Thanks for all of the replies! I figured it was going to be a make shift deal and yes, this would definitely be the time to put a shut off valve on both sides. I like the barb idea too. I'm not sure which unit is in there. We got back from a Labor day trip and I haven't done anything other than dry the bay out where the water was running too. It is an electric/propane combo unit. I'll most likely do my research and purchase the unit over the winter and then do the install come spring time when it comes out of storage.
Thanks again.

Some People make this into a big labor operation and messy. As Old Biscuit stated, just clamp off the 2 lines with needle nose Vise Grips. The fluid that will leak out when removing is about 1 cup worth. This is a good time to install 2 cut off valves, so in the future you can cut off the hoses easily when doing any type repair to the water heater. Doug

I had to bite the bullet when changing out mine! I actually didn’t make to big a mess ,caught 90 % of the fluid in an old towel. I prepared for the deed by purchasing a brass coupler and hose clamps
I couldn’t find a correct replacement tank so went with what was available at the time .
As a result I no longer have an engine heated water heater.
I simply installed the brass connector between the hose ends.
Am currently considering installing a radiator style heater similar to what’s under the seats in school buses to augment the forward heater in the cab utilizing that handy loop of engine coolant!

Why couldn't you take the lines loose at the engine and blow them out before taking them loose at the water heater?

Clamp each hose shut with vise grips....2 small pieces of wood between the jaws

What Brand/Model is this water heater?
Combo unit...electric & propane?

If Atwood the Newer version may be the only replacement......depends on current Model.
Newer version requires changes/modifications in AC & DC wiring...not difficult just some adding of DC circuit and Mod to AC circuit

you could push a barbed plug in the hose when you take it off.good time to install shut off valve.

Do it when the engine is cold and no pressure on the radiator. A pan should catch most of what little you are going to have. The heater itself will have some.

You also could push out with air ,but that could cause air in the system. Drop a couple gallons out of the radiator also should help.

Remember to top off the fluid once it change out.