pex line length

My wife and I will be tackling the installation of the water supply system in our new house next year and we have decided to go with a home run system using the Manabloc manifold and pex. The only part that troubles me about the design/installation is the length of the hot/cold runs to the master bath. We're installing the Manabloc in the basement, nearest the the majority of the fixtures. However, the master bath is on the oppsoite end of the house from the Manabloc. In looking at the blue prints I would estimate that the length of the runs would be around 80-90 ft. Will this create a significant reduction in pressure or wait time for hot water?

It will create a time delay, no matter what type pipe is used. You might want to consider installing a well-insulated return line for a recirulator pump.

Because of wall-thickness, PEX carries less volume than copper, so for a 90" run use minimum 3/4, and depending on what your usage might be you could even consider 1"

The Manablock manifolds I've seen use 3/8" runs to the fixtures. And many runs are 40-80'. With 3/8" pigtails on all sinks, why would more water be needed when all sink faucets are flow controlled at 2.5 gpm anyway? I'd go 1/2" to the tub faucets and showerhead but the showerhead is flow controlled at 2.5 gpm again. So I don't see a need to increase the ID very much, especially when I know that PEX is slicker than copper and the very small ID difference isnt' all that great to begin with, and there are only two fittings in the 80-90' homerun; one on each end.

Gary
Quality Water Associates

Thanks Gary. It helps to have someone who has actually seen one of these systems. I can't seem to find anyone in my area who uses pex or knows anything about the manifold. The Manabloc I'm using has both 3/8" and 1/2" ports and from my research I didn't think the length of the run would make much of a difference but it helps to get some other opinions.

I thought there were a few 1/2" ports on their manifold but couldn't remember for sure.

A fair number of my water treatment customers around the country have the Manabloc or use PEX in branch and tee plumbing. It is being used more and more just about everywhere. I don't use much of it but I have used PB and a lot of PE tubing. I think they are great materials IF USED and INSTALLED correctly.

Gary
Quality Water Associates