Just a little background. I have a pool house that I installed a kitchen sink with hot and cold water. The pool house is supplied with water by means of a pvc pipe running underground to a sillcock about 30' away. The pvc pipe is attached to the sillcock with a short piece of garden hose (all threaded joints). Under the sink cabinet in the pool house I have a Titan (made in Italy, bought at HD) 2.5 gal electric water heater to make the hot water for the sink. The pvc supply pipe has a tee fitting with one side going to the cold side of the sink and the other side going to the heater and then to the hot water side of the sink. The sink drains into a septic tank 20' away. Every year in the late fall, I take the portable water heater out, disconnect the garden hose connector, and drain the pvc pipe. I also take the sink trap out. Over the NY winters, I store the heater in my attached garage.
Now, for my question (finally!). I have a half bath on the opposite side of the house from my propane water heater. Everytime I need hot water there, I have to let the water run for a few minutes before it gets hot. Can I use that electric water heater under the 1/2 bathroom sink feeding from the house's hot water line? In other words, rather than having the cold water line going into the heater, it would be getting the water from the house's hot water line. I doubt whether we would ever use 2.5 gals of hot water at one time there, so the hot water line coming going into the heater would probably never be really hot. This would be just for the winter months when the elec. heater is just sitting idle in the garage. I can't think of a logical reason not to do it, but maybe someone else has done it, or knows why it shouldn't be done. I may not install the heater anyway, but if I get ambitious (or really pissed off waiting for hot water), I'd like to know beforehand.