New const. plastic line question

I am thinking of having a house built. I hate to waste water while waiting for the hot water to get to the taps. Has anyone seen or heard about running one plastic line to each bathroom and then installing a on demand water heater in each bathroom? My thinking is it would cut down on installation cost by not having to run the hot water line, at the same time saving water by not having to wait for it to run the length of the house to get to the tap. Any thoughts or ideas would be great.

I believe you should investigate a recirculating pump. There are several kinds available and they work very well. I have one that has be in 24/7 operation for over 4 years. They also come with timers so they only operate when hot water will likely be called for. Mine is a Laing, it requires a return line from the most distant point of use. I have never felt the cost of operation to be very of concern. I did insulate my hot water lines including the return line. These can be difficult to retro fit in some cases, but in new construction, it would be very simple. There are some recirculation systems that do not use a return line. My son recently had one installed and it seems to work very well also. Aside for water conservation, you will love the instant hot water. I recommend using copper, rather than CPVC.

Well, a tankless at each usage location would save some on piping costs, but those units are expensive, and the gas or electric installation for each would more than exceed the water pipe savings. It would work well, but those units also have MANDATORY semiannual maintenance, like flushing with mild acid etc.

Recirc system is easier and works well.

heaters

"On demand" and "tankless" are two different animals. An on demand heater is only adequate for one or two faucets and even then the flow rate is abysmal. To get adequate flow, you have to discard the heater supplied aerator and then the flow is too rapid for the water to heat. The ONLY benefit to a tankless heater IS that it can be installed in the area of use, but the logistics of gas and flue, or electric power supply, plus the cost of the units usually precludes doing so.

Thanks for the help. I will do some research on the recirculating system with a water heater. I am sure will have more questions.

Gary Swart said:

I recommend using copper, rather than CPVC.

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When I hear DIYers mention "plastic" I assume they mean PEX. (Cross-linked Polyethylene.), which I would recommend over copper as the return line will have more turbulence than normal from the recirculation going on.

You might be right about plastic = pex, but to me plastic = pvc, abs, or cpvc.