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75' Pex Run - Home Run vs. Remote Manifold

oldhouse7's picture

I'm replacing the original supply pipes in a 95 y/o house and am looking for some advice given the inefficient location of the boiler (which provides the hot water) and fixtures (kitty corner from one another).

There are 23 fixture units, the farthest being 75' from the boiler, though most fixtures are not significantly closer than this. There will likely be front and rear irrigation added in the future, which I believe would up the fixture units by 5.

Given the long run lengths, what's the most efficient setup in this scenario, which will prevent pressure drops while running multiple fixtures AND get hot water there the quickest?

What are you asking? (post #215784, reply #1 of 4)

The choice is not a manafold vs a home run. You can make homeruns from each fixture or you can make one home run from a manafold or multiple Ts. You will need a 3/4" HR for both hot and cold. You will never get hot water quickly without a circulating pump. Since you have to make home runs any way you could include a 1/2" return for your pump. This would be better than a retrofit pump that uses the cold water run. As to pressure, think about a seperate HR for the irrigation. 

Put another way - I can (post #215784, reply #2 of 4)

Put another way - I can locate the manifold near :


 - the boiler (which provides HW) have home run lines of some diameter running ~75 feet to each fixture  or

 - the fixtures (say, within 15 feet) and run one main line hot one cold main line  from the boiler to the manifold.

One HR (post #215784, reply #3 of 4)

Run one home run and use a manafold. If it's more convenient use Ts. Even thoough PEX lends itself to manafold installation there's nothing wrong with Ts just like copper. Do you already have cold to that location? Consider the cold return for a circulating pump.

Points of view have changed (post #215784, reply #4 of 4)

Points of view have changed in the past 95 years.  It used to be (in part because of the cost of the pipe) that using a single pipe (large enough to supply all fixtures) was preferred to individual (smaller) pipes.

However, with the reduced cost and better ease of installation of flexible plastic pipe, many perceive an advantage to using a separate (smaller diameter) pipe for each fixture (or at least each separate bathroom), in part because the smaller diameter pipe "stores" less water and hence hot water can "'arrive" 2-3 times faster.  (The other big advantage to separate pipes is less pressure change when someone flushes the toilet in the next room while you're takign a shower.)

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville