In the log cabin we built, there is a loop for both bathrooms.
the shower on the first floor has INSTANT hot water, the sink, no
and the upstairs bath also does not get hot as quick, but it is quicker then a "normal" plumbing setup.
the hot water heater is in the basement of this home.
in my other buddies house, who has been plumbing for 25+ years, and is the one who installed the plumbing in the cabin also.
he put in a loop but added a pump, this is what he says of his house.
<UL TYPE=SQUARE> You need to insulate the hot water line with at least 1" thick insulation and then it will cost you almost nothing to run the pump especially if you use a pump with a timer.
Best way I know of is a timer on the pump set at high usage periods or leave it run 24/7
What type of water lines is he using?
Copper, Pex or CPVC or something else?
If Pex is he using the manifold system or just a standard branch line system?
Tankless water heater or tank type?
Gas or electric?
Crawl space or basement?
If he goes tankless it pretty much defeats the purpose.
All I've seen, cause the heater to run constantly to keep the water warm.
Won't be to bad if he uses a 2 stage style so that it runs on the lower stage for heating the recirc water.
My self if I had natural gas I'd use several smaller tankless water heaters located by each bathroom group and one by the kitchen unless it's close to a bathroom. This way there are fewer hot water lines to run, no recirc line and not constantly heating a tank full of hot water.
Down side is you have to have a place to put the heaters and run more gas lines.
If he's in the country my advice is copper or CPVC.
Pex is not rodent proof and if mice, rats, squirrels or any other critter needs water they can smell it through the pex and will chew a hole to get to it.
Had it happen at my house, mice chewed through my dishwasher line to get water.[/list]
hope it helps,
any-other questions i can send them to him or you can PM me and i will get his email address to you.