Home>Discussions>PLUMBING>pex plumbing system with new home construction
2 posts / 0 new
Last post
wags1970
pex plumbing system with new home construction

I am going to be having a new home built. It will be a single story home approx 2,000 sq ft with a full basement. I'm trying to plan out the best plumbing system and distribution design that makes the most sense. I am going with PEX. I was thinking about the home run system, but have also seen somewhere where someone preferred to have a modified version where there were a couple of manifolds that were closer to the fixtures rather than a single manifold, as it results in waiting a long time to get hot water to the faucets. I saw somewhere else where someone mentioned having a temperature sensitive recirculation valve so it will feel like I have hot water on demand. Anyone have any thoughts on what works best. Does a single manifold really produce a long wait time for hot water as compared to a traditional trunk and branch copper system found in most homes? I realize "long wait" can mean a lot of different things to people, so I'm not really sure if its a factor or not. Looking to get some opinions, as I'd like to be informed so I know that my plumber will be giving me the best design for me. By the way, the home will have 3 full baths. 2 of them will be very close together, the other will be on the other side of the home. I wouldn't anticipate any run being longer than 40-50 ft from the distribution manifold, which is yet to be determined where it will be located. Thanks

Fencepost
Re: pex plumbing system with new home construction

If you search these boards, you'll find plenty of debate on PEX vs. copper, so I won't get into THAT here.

A manifold system will likely result in hot water getting to remote fixtures FASTER than a trunk/branch system, since the total volume of cold water that must be evacuated from the line is less since there are smaller pipes involved. However, in a trunk/branch system if one fixture recently used hot water, another fixture will receive it sooner since there is already some amount of hot water in the line.

In a true trunk/branch system, you would have a single trunk line that gets progressively smaller as fixtures are tapped off of it. The trunk goes by each fixture, resulting in a relatively short line from the trunk to the fixture. In reality, most installations actually have branches off of branches.

Implementing a recirculating system becomes much more difficult with a home-run manifold system than a trunk/branch system, as there is a "dead end" on each line that must be dealt with. The easy way to deal with this is to use a thermostatic valve at each fixture, redirecting the cooled water from the hot line back into the cold line, and having a recirc pump on the water heater.

A recirc system on a trunk/branch system can be done the same way, or you can simply run a return line from the farthest fixture back to the water heater, where a recirc pump pumps it back into the cold supply at the WH. This is simplest with a true branch system; otherwise you would have to install multiple return lines and thermostatic valves.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.