# Reduced flow from pex fittings?



## Nikolai

Does the smaller I.D.(3/8") of 1/2" pex fittings, compared to copper pipe, restrict the flow enough to directly affect the water pressure at tub spouts and shower heads? Would a bathtub fill faster if the water piping was done in 1/2" copper, or is the valve the limiting factor here?

The previous company I worked for installed per in every house, and it never seemed to be an issue, but I'm curious what you guys think.


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## ILPlumber

Yes


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## express

Yes. You can not use pex from the valve to the spout on most valves or water will always run out of the shower head


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## 422 plumber

It won't affect pressure, but the volume is decreased. If you do a manabloc, it probably doesn't matter much. If you do a trunk and branches, I would use 1/2" only to the last fixture.


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## Nikolai

We always ran 3/4" or 1" trunks with 1/2" branches to each fixture. I'm getting ready to do all the water piping in my personal home and can't decide between pex and copper. Pex is cheaper and faster to install, but part of me just doesn't like the reduced ID.


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## Chauncey

*Go with Uponor Pex*

Go with an Uponor manifold system 1/2" to all fixtures, shut offs at the manifold. The external expansion rings are foolproof. Use the EP fittings(plastic) never a problem. I'm re-piping my own house, new mod con boiler and indirect all will be piped with Uponor. I will post the pictures when I'm done. Good luck what ever you decide to do.


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## plumb nutz

Now that looks nice...

Wish all you pex plumbers could teach the guys down here how to run that stuff...


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## Bill

When I use pex I ALWAYS run a 3/4 main and use a 3/4 tee. Then where it stubs out the wall I turn out with a 3/4 x 1/2 90. I never have any trouble that way


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## Redwood

Nikolai...

You may find this useful if you have not read it yet...

http://www.toolbase.org/pdf/designguides/pex_designguide.pdf


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## Nikolai

Now that's some good information, thanks for the link.


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## Prscptn Plmbng

Chauncey said:


> Go with an Uponor manifold system 1/2" to all fixtures, shut offs at the manifold. The external expansion rings are foolproof. Use the EP fittings(plastic) never a problem. I'm re-piping my own house, new mod con boiler and indirect all will be piped with Uponor. I will post the pictures when I'm done. Good luck what ever you decide to do.


You must wait forever to get hot water to some of those branches


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## Widdershins

Prscptn Plmbng said:


> You must wait forever to get hot water to some of those branches


 When I use manifolds I use the flow through ones, place them close to the bathroom/kitchen/laundry etc and use the outlet as a return to the circ pump.

Insulating the lines to retain heat also helps.


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## Redwood

Widdershins said:


> When I use manifolds I use the flow through ones, place them close to the bathroom/kitchen/laundry etc and use the outlet as a return to the circ pump.
> 
> Insulating the lines to retain heat also helps.


I usually do a trunk and branch but in a larger home may do small manifolds near the point of use. Recirc can be done from the manifold....


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## Chauncey

Prscptn Plmbng said:


> You must wait forever to get hot water to some of those branches


Longest HW run is about 15 ft. It takes about 12 seconds to get HW at the faucet. 3 bedroom ranch with 3 full baths. Everybody's in a big hurry. Hot water recirc is a giant waste of materials and energy in a home this size. 25' X 48' the customer is very satisfied.


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## Widdershins

Redwood said:


> I usually do a trunk and branch but in a larger home may do small manifolds near the point of use. Recirc can be done from the manifold....


You'd be surprised at just how many folks don't realize you can circ a manifold.


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## Redwood

Widdershins said:


> You'd be surprised at just how many folks don't realize you can circ a manifold.


Well if it is sitting next to the meter you won't gain much...

But remote manifolds are the cats azz... :thumbup:


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## Widdershins

Redwood said:


> But remote manifolds are the cats azz... :thumbup:



Yes they are.:thumbup:


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## voltatab

I contacted uponor one time cause I was concerned about the id of pex also. In fact I think I even posted about it once. 

The uponor rep stated that the smaller size does not affect the amount of water gettingto each fixture, and that stepping up on size is not needed cause the velocity Is faster though pex than copper so it makes up for the diff. 

Yet plumbers (the Guys installing and liable for the plumbing) say that's BS. Dont know if they speak from experience or just being safe.


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## Nikolai

That's a good point as well. My hot and cold trunks will only be around 50 ft. and all the branches are direct shots to the fixtures and less than 8 ft.


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## Prscptn Plmbng

Widdershins said:


> When I use manifolds I use the flow through ones, place them close to the bathroom/kitchen/laundry etc and use the outlet as a return to the circ pump.
> 
> Insulating the lines to retain heat also helps.


Ya thats the way I've been doing for quite time...

Prescription Plumbing Inc 
P.O.Box 6378 
Oceanside, CA 92502


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## Prscptn Plmbng

Chauncey said:


> Longest HW run is about 15 ft. It takes about 12 seconds to get HW at the faucet. 3 bedroom ranch with 3 full baths. Everybody's in a big hurry. Hot water recirc is a giant waste of materials and energy in a home this size. 25' X 48' the customer is very satisfied.


Thats bout how long it took me to get my car insurance...jk 

Twelve seconds adds up, it's more about the water savings than the quickness of the system. When your in a stage two drought zone and prices break the bank, customers will pay to save water...

Not to mention it's the green thing to do...

I was impressed with your system, not to many plumbers out there that do clean work....

Prescription Plumbing Inc 
P.O.Box 6378 
Oceanside, CA 92502


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## Prscptn Plmbng

voltatab said:


> I contacted uponor one time cause I was concerned about the id of pex also. In fact I think I even posted about it once.
> 
> The uponor rep stated that the smaller size does not affect the amount of water gettingto each fixture, and that stepping up on size is not needed cause the velocity Is faster though pex than copper so it makes up for the diff.
> 
> Yet plumbers (the Guys installing and liable for the plumbing) say that's BS. Dont know if they speak from experience or just being safe.


Speaking from experience... Thats bs... I fell for that in my rental... I plumbed it as if it were copper and got screwed... It's a good thing I put positemps in....

Plus speeding up velocity will errode the pipe just as copper... 

On a branch layout system, upsize it.. On a hybrid system your fine cuz only the drops are 1/2"

Prescription Plumbing Inc 
P.O.Box 6378 
Oceanside, CA 92502


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## voltatab

What's a hybrid system?


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## Prscptn Plmbng

voltatab said:


> What's a hybrid system?


A mix of trunk main lines and flow thru manifolds, in uponor's manual they had three choices of how to run their pipe, branch, manifold and mixed... It's been so long since I've opened it I could be calling wrong but the basic principles are right.

Prescription Plumbing Inc 
P.O.Box 6378 
Oceanside, CA 92502


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## Protech

voltatab said:


> I contacted uponor one time cause I was concerned about the id of pex also. In fact I think I even posted about it once.
> 
> The uponor rep stated that the smaller size does not affect the amount of water gettingto each fixture, and that stepping up on size is not needed cause the velocity Is faster though pex than copper so it makes up for the diff.
> 
> Yet plumbers (the Guys installing and liable for the plumbing) say that's BS. Dont know if they speak from experience or just being safe.


That's true in some respects, but not all. It's true that you can size pex system the same as a copper system and the pex system (in most cases) will not cavitate it self to death. However, in most cases you wil NOT get the same flow pressure that you would get from the same size and shape copper system.

I hope that clears it up for you. If not, let me know.


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## shakeyglenn68

I have always ran a branch system 1" to the second to the last fixture (hot and cold), Then 3/4" from there on. Reduce it down to 1/2 right before stub out. The last fixture on the hot would have a 3/4x3/4x1/2, 1/2 being stub out, then ran 3/4 non broke to circ. No wait time hot water in less than a sec. 

Never used PEX from valve to spout always used copper. Did us PEX from valve to shower dropped ear L but didn't worry over pressure drop for orifice (metering device) in shower head, If it was a rain maker used copper. 

It all cost more but the customers we had didn't complain.


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## SIR_SAILSALOT

Nikolai said:


> Does the smaller I.D.(3/8") of 1/2" pex fittings compared to copper pipe, restrict the flow enough to have a direct effect on the water pressure at tub spouts and shower heads? Would a bathtub fill faster if the water piping was done in 1/2" copper or is the valve the limiting factor here?
> 
> The previous company I worked for installed pex in every house and it never seemed to be an issue, but I'm curious what you guys think.


I have studied FLUID DYNAMICS and can tell you from that perspective certain YES 1/2" will fill faster if all other things are equal . 
But there are some things to consider. 
Each PEX fitting has a restriction. The more restrictions, the more pressure drop.
Each bend in a copper run does the same. 
Example, I am in the process of changing all my copper to PEX because the existing copper system was a maze created with a crazy number of elbows and unnecessarily long copper runs (and btw ran in outside walls etc so prone to freezing).
The PEX will be a HOME RUN straight to each fixture with large smooth curves if necessary. 
SO the wind up
I save on pressure drop because runs will have far fewer 90's and shorter runs.
I have larger but far fewer pressure drops on each run with 2 pex fittings. per run. 

Copper will fill faster provided care is taken to plan well and it is professionally done.
I will be interested to hear professional plumbers comments. 

Not sure what to think but I am considering either 3/4" PEX on tubs and showers and 1/2" on toilet and sinks.


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## SIR_SAILSALOT

voltatab said:


> I contacted uponor one time cause I was concerned about the id of pex also. In fact I think I even posted about it once.
> 
> The uponor rep stated that the smaller size does not affect the amount of water gettingto each fixture, and that stepping up on size is not needed cause the velocity Is faster though pex than copper so it makes up for the diff.
> 
> Yet plumbers (the Guys installing and liable for the plumbing) say that's BS. Dont know if they speak from experience or just being safe.


Sorry but the UPONOR rep is wrong. He is mixing up pressure and flow. Restriction = Pressure Drop= Less flow. 
Think of this experiment. Take your garden hose with what ever nozzle you have Put it on the most forceful high pressure setting you can manage and still fill a buck. Fill a large bucket (1/2 way maybe) and time it. Now take the nozzle completely off so its just the hose. Repeat the experiment. 
Less restrictions = Slower speed = larger flow
Means more pressure for your shower head and faster filling for your tub.


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## sparky

SIR_SAILSALOT said:


> Sorry but the UPONOR rep is wrong. He is mixing up pressure and flow. Restriction = Pressure Drop= Less flow.
> Think of this experiment. Take your garden hose with what ever nozzle you have Put it on the most forceful high pressure setting you can manage and still fill a buck. Fill a large bucket (1/2 way maybe) and time it. Now take the nozzle completely off so its just the hose. Repeat the experiment.
> Less restrictions = Slower speed = larger flow
> Means more pressure for your shower head and faster filling for your tub.


Your talking mad


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## SIR_SAILSALOT

Its physics


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## Logtec

It’s ScIeNcE!


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## skoronesa

Logtec said:


> It’s ScIeNcE!



Did she blind you?


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