I never had problems posting photos before, but these last few days it appears that I am blocked. I'll do some research to see if I can locate the problem.
The mod was rather easy on my trailer, pulling a hose through the furnace area, under the shower and up into the vanity area took an hour or two. I was able to connect to one of the two fresh water tank vent lines with a Y aiming it down stream towards the tank. Under the vanity, I just used a T in the hot water supply to the faucet. Then a quarter turn valve was added in the newly added hose. While I was at it, I also added shut-off valves to the faucet.
Some trailers may be easier and some may be next to impossible, it's just a matter of what you have to do to tap into the tank and fish a hose to the vanity. If it is a very short run, the water saving may not be great, but you would still have the tank heating benefit.
This is a rather simple job, and no need for adding pumps as has been posted here before.