Any plumbers here that work with PEX a lot?

[gregkl]

I'm plumbing up a couple bathrooms and I am thinking I want to build a manifold with home runs to each fixture. I have been reading that it is beneficial to include a loop to help balance the flow/pressure. Is there any advantage to designing a manifold like the one below?

 

[JettaKnight]

I thought you can just buy a manifold with nice shut-offs and a large chamber.
https://www.menards.com/main/search.html?sf_categoryHierarchy=&search=pex+manifold



On all of those the main feed is large enough, and all the ports are within one inch, so there won't be any difference in pressure from first to last port. The sizing of the main feed should be large enough that if you're using a faucet on one port, it will have a constant flow if you flush a toilet on another. I would suspect that all of those manifolds are capable of that.


If you had multiple manifolds spaced out throughout the house, then having a loop back at the start could help.

 

[ghitch75]

you will get better flow running 3/4" then branching drop to 1/2" with valves on each......the manifolds don't flow very will.....i work with pex everyday day in and day out....

 

[gregkl]

I thought you can just buy a manifold with nice shut-offs and a large chamber.
https://www.menards.com/main/search.html?sf_categoryHierarchy=&search=pex+manifold



On all of those the main feed is large enough, and all the ports are within one inch, so there won't be any difference in pressure from first to last port. The sizing of the main feed should be large enough that if you're using a faucet on one port, it will have a constant flow if you flush a toilet on another. I would suspect that all of those manifolds are capable of that.


If you had multiple manifolds spaced out throughout the house, then having a loop back at the start could help.

I had a spin closed manifold to use with home runs to each fixture but I did some reading (dangerous) that stated that the last outlet sometimes gets less pressure/volume? if an outlet upstream is opened. They said to use a straight thru but I don't have anyplace to go so I thought I'd just make a loop thinking that the water will flow both ways though I am no plumber or hydrologist for that matter.

you will get better flow running 3/4" then branching drop to 1/2" with valves on each......the manifolds don't flow very will.....i work with pex everyday day in and day out....

So run it like a standard trunk and branch system? 3/4" to general area then 1/2" branches to one fixture, then another and so on?

If it helps paint a picture, I have two bathrooms sharing a common wet wall. Bath one has one tub/shower, toilet and lav. Bath 2 has toilet, 2 lavs and one shower with two separate shower valves. There is a possibility that either both lavs or both shower valves will be running at the same time.

 

[Longhair]

By code you can only feed two fixtures off 1/2" , What ever you do don't use one of the plastic manifolds, pure junk roll your own with brass ball valves if you must. Just go 3/4" main to 1/2" branch feed. If you have a leaky commode it's much easier to turn the water off @ the fixture than to race to your fancy looking manifold.
.

 

[gregkl]

By code you can only feed two fixtures off 1/2" , What ever you do don't use one of the plastic manifolds, pure junk roll your own with brass ball valves if you must. Just go 3/4" main to 1/2" branch feed. If you have a leaky commode it's much easier to turn the water off @ the fixture than to race to your fancy looking manifold.
.

I wasn't planning on using any valves on the manifold. I have the whole house shut off near where these would go and I have the individual shutoffs at each appliance. I don't see the need for all the valves some of these guys use. To me they are unnecessary expense and a potential point of failure. They claim it makes it easier to shut off the one run when it leaks vs the whole house, but I've had one pipe/fitting leak in all the years I have lived in houses and it was the riser to a kitchen sink. (knock on wood). I would maybe consider one valve just before the manifold so I could cut that off in case of something happening and at least I would still have the kitchen and 3rd bathroom operable.

 

[Mark-DuCo]

Is there really any benefit to the manifold? Seems like a lot of extra pex to be making home run for every toilet, faucet, shower, etc.

 

[Clay Pigeon]

Is there really any benefit to the manifold? Seems like a lot of extra pex to be making home run for every toilet, faucet, shower, etc.

Pex tubing is cheap, I homeruned my house so I wouldn't have any fittings behind the sheetrock.

 

[JettaKnight]

I had a spin closed manifold to use with home runs to each fixture but I did some reading (dangerous) that stated that the last outlet sometimes gets less pressure/volume? if an outlet upstream is opened. They said to use a straight thru but I don't have anyplace to go so I thought I'd just make a loop thinking that the water will flow both ways though I am no plumber or hydrologist for that matter.

How could there be any pressure differential over a span less than twelve inches?

 

[JettaKnight]

Pex tubing is cheap, I homeruned my house so I wouldn't have any fittings behind the sheetrock.

This.

 

[gregkl]

How could there be any pressure differential over a span less than twelve inches?

Like I said, I'm no hydrologist. I'm trying to understand some of the internet chatter about how to configure these systems optimally. I was fine with making a home run system but read about a few tradesman who said that adding a loop would help.

If it won't do anything but add to my workload, then I am happy to skip it.

 

[Mark-DuCo]

Pex tubing is cheap, I homeruned my house so I wouldn't have any fittings behind the sheetrock.

Ah, I guess it isn't too bad. I just ran a cold, hot, and return for recirculating pump to the shared wall between my two bathrooms and branched out from there. In my case it would have been a good 400ft of extra pex to have a home run for everything.

 

[Clay Pigeon]

Ah, I guess it isn't too bad. I just ran a cold, hot, and return for recirculating pump to the shared wall between my two bathrooms and branched out from there. In my case it would have been a good 400ft of extra pex to have a home run for everything.

To run a recirculation pump you wouldnt home run each fixture...

 

[gregkl]

Ah, I guess it isn't too bad. I just ran a cold, hot, and return for recirculating pump to the shared wall between my two bathrooms and branched out from there. In my case it would have been a good 400ft of extra pex to have a home run for everything.

400’ would have me reconsidering too! My runs are less than 12’ from the water heater with the exception of the shower which is less than 20’. Roughly 100’ of each color should get me done.

 

[gregkl]

I did some reading in the Residential PEX Water Supply Plumbing Systems handbook. The book is backed by the PPI, PPFA and others so I'm going to trust they wouldn't steer me wrong.

Like some of you have said, I'm going back to my original idea and will be doing a home run system. I only have 6 hots and 8 colds sharing a common wet wall (other than the shower which is an additional 8' away) so it won't be too difficult to run it all.

Thanks everyone for your input. I find it interesting that I get input from a gun forum when the plumbing forums like Terry Love and John Bridge are virtually unresponsive and most of their threads are several years old.

Now to decide whether to make my own manifold or buy one.

If I made one, I think it would be like this:

 

[JettaKnight]

I did some reading in the Residential PEX Water Supply Plumbing Systems handbook. The book is backed by the PPI, PPFA and others so I'm going to trust they wouldn't steer me wrong.

Like some of you have said, I'm going back to my original idea and will be doing a home run system. I only have 6 hots and 8 colds sharing a common wet wall (other than the shower which is an additional 8' away) so it won't be too difficult to run it all.

Thanks everyone for your input. I find it interesting that I get input from a gun forum when the plumbing forums like Terry Love and John Bridge are virtually unresponsive and most of their threads are several years old.

Now to decide whether to make my own manifold or buy one.

If I made one, I think it would be like this:

View attachment 82965

Well, there's less joints, and looks cleaner if you buy one.


(I can't believe I'm not advocating DIY)

 

[bcannon]

Buy your manifolds, in brass not plastic. You would have less opportunities for future leaks and less time involved. My

 

[gregkl]

Well, there's less joints, and looks cleaner if you buy one.


(I can't believe I'm not advocating DIY)

Good point. And since the manifold is 3/4" with 1/2" stub outs, it would basically be same as what I would build except that mine would be larger and less rigid.

I would definitely do brass and not plastic. There are those that say you can use plastic fittings instead of brass but I like crimping down on brass better.

 

[Thor]

If you run individually to every fixture just realize that after you take your hot shower when you walk to the sink it's still a 30sec+ wait for hot water there. DAMHIK.

 

[JettaKnight]

If you run individually to every fixture just realize that after you take your hot shower when you walk to the sink it's still a 30sec+ wait for hot water there. DAMHIK.

Why do you need hot water at the sink after you take a shower?


EDIT: had to look up that acronym... so I guess you can ignore the question.