Diagrams - photos

Not mentioned yet but it does not have to be an either/or solution.  If you are hooked up to electric and use alot of hot water you can heat with BOTH electic and propane at the same time.  You will get hot water much faster and very little propane is used to heat a 6 gal tank.  We use both all the time we are hooked up.  In our new RV the inside panel has two switches side by side for hot water so it is simple to use both.  But as stated before, running out of water while electric is on will burn out the element which is why many manufacturers put the electic switch out of the way

Originally posted by TheBum [QUOTE=Andiamo] Thanks. Stoopid to have to do this. Did govt design the original?  (I can say that being a Forest Service retiree!)

You can, as you said earlier in the post, just leave the outside switch on all the time and flip the switch in the breaker panel to turn it on/off. It is perfectly acceptable to do that.

Most of the designs that the "government" uses are the brainchildren of government contractors from private industry.  They just get adopted by the government official after a nice vacation sponsored by the contractor.

Here's the switch I put in.  The 172 has the water heater on the port side aft of the refrigerator and heater under the dinette so it's easy access.  

This was discussed in another topic, but adding a switch inline with the breaker to the water heater and mounting that switch in a convenient location is one option. Just make sure the switch is rated for sufficient voltage and current.