PEX House Re-pipe

[thedayrock]

My house has galvanized plumbing which has been rusting internally and has had issues with leaks.

I plan on re-piping with PEX-A and using the home run system with a Uponor Manifold. My water pressure is 52 psi and I have the following lines:
Laundry
Kitchen Sink
Dishwasher
Fridge Ice Maker
Wet Bar
3 Bathrooms.

I was planning on using 1” supply to the manifold and water heater and then 1/2” home run lines for the fixture.

Please help advise me and give your honest unfiltered opinions!

 

[thedayrock]

Manifold or Trunk and Branch?

 

[Sponsor]

 

[JohnCT]

Manifold or Trunk and Branch?

I'm wondering the same thing. I'm replacing my copper trunk and branch with PEX in my two story colonial, but am thinking about using smaller manifolds and putting them in the ceiling between the first and second floors to feed the two full baths upstairs. So the plan is to keep the two 3/4" hot/cold sources from the basement into the ceiling in the kitchen, but use multi tap 3/4 to 1/2 manifolds to feed the upstairs fixtures.

I'm just not sure whether it's a good idea to use that many expanded connections behind a sheetrock ceiling. If I had easier access, I'd do a home run system I guess.

Sorry I can't be of more help.

John

 

[Reach4]

An advantage of 1/2 inch to each bath is that the delay to get warm water is less than if you run 3/4 inch. For cold it would not matter. If you are doing recirculation over the 3/4 inch part, then that factor should go away.

3/8 would have the advantage of hot water sooner for lesser loads. Unfortunately 3/8 stuff in Aquapex/expansion/pex A is more rare.

 

[thedayrock]

Would water pressure be an issue for that many home run lines? The branches could be 75 feet for some runs!

 

[JohnCT]

Would water pressure be an issue for that many home run lines? The branches could be 75 feet for some runs!

Seems to me the only time pressure would be a problem is the very first time you fill the total system after installation. After that, pressure should be a function of how many fixtures are in use at the same time, but I don't see length or amount of pipes affecting pressure.

 

[Reach4]

Seems to me the only time pressure would be a problem is the very first time you fill the total system after installation. After that, pressure should be a function of how many fixtures are in use at the same time, but I don't see length or amount of pipes affecting pressure.

Page 5 of these Pressure Loss Tables shows pressure drop for 1/2 inch Aquapex per 100 ft. You could also allow for some drop from fittings. I might figure 6 gpm for a tub, 3 gpm for a shower. 1 or 2 gpm for a lavatory.
https://www.uponorpro.com/~/media/Extranet/Files/manuals/PressureLossTables_H191_1210.aspx?sc_lang=en

 

[JohnCT]

Page 5 of these Pressure Loss Tables shows pressure drop for 1/2 inch Aquapex per 100 ft. You could also allow for some drop from fittings. I might figure 6 gpm for a tub, 3 gpm for a shower. 1 or 2 gpm for a lavatory.
https://www.uponorpro.com/~/media/Extranet/Files/manuals/PressureLossTables_H191_1210.aspx?sc_lang=en

What I meant is that the length of pipe will be the same no matter if he runs a single branch or individual home runs. Either way, the fixtures are 75' away. Shouldn't make a difference in pressure, no?

 

[Reach4]

What I meant is that the length of pipe will be the same no matter if he runs a single branch or individual home runs. Either way, the fixtures are 75' away. Shouldn't make a difference in pressure, no?

When we say pressure in this context, we imply pressure at the fixture during flow conditions.

So for a given flow, 1/2 inch will have more pressure drop. However 3/4, holding more water, will take about twice as long for warm water to arrive.

If doing two simultaneous bath fills, separate 1/2 or shared 3/4 will have similar pressure drops.

 

[thedayrock]

Any suggestions on PEX-A manifolds? Copper or DIY?

 

[Michael Young]

Manifold or Trunk and Branch?

TRUNK AND BRANCH 100%
if you're doing it for yourself, install a big juicy 1" gutline for both hot and cold and pull off that gutline. I run full-port to every fixture group.

 

[thedayrock]

Would you mind explaining why trunk and branch is preferred?

 

[Michael Young]

Would you mind explaining why trunk and branch is preferred?

The reason I HATE manifold systems is because you end up with massive clumps of 1/2" pipe. For instance. Trunk and Branch.... you pull a gutline for hot and cold (one line each). And then simply pull three colds (toilet, lavatory, shower) and two hots (lavatory, shower). It's sleak and simple. And the less time you spend in the crawlspace (trust me on this), you'll thank me later.

If you use a manifold, you will have FIVE HALF INCH LENGTHS OF PIPE making home a home run back to your manifold. And you are required by code to strap every damned one of 'em. (enjoy your time in that crawlspace). Manifold will waste a ton of time and there is no real win. If you want the best of both, cut in a 3/4" full port ball valve before you hit each fixture group.

I feel strongly enough about this that if a homeowner insisted on me installing a manifold system, I would insist that he call another plumber. manifold system, pffft. It just ain't worth it.

 

[thedayrock]

Thanks for the feedback!