# Is 1/2" PEX tubing enough?



## rjniles (Feb 5, 2007)

If each fixture will have a home run to the manifold, 1/2 is fine. If the run will feed multiple fixtures, use 3/4


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## Homerepairguy (Aug 1, 2010)

rjniles said:


> If each fixture will have a home run to the manifold, 1/2 is fine. If the run will feed multiple fixtures, use 3/4


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I'll be running trunk and branch lines to our bathrooms, laundry room and kitchen. 
- So I'll run a 3/4" trunk line to our back-to-back bathrooms. Thanks for the confirmation.

Regarding our laundry room and kitchen. 
- Our laundry room has a laundry tub and a washing machine. We normally don't use hot water to wash our clothes so I'm thinking of running a 1/2" trunk line and branching to those two fixtures. This trunk line will be about 45' long.

- Our kitchen has the sink and a dishwasher. I'm thinking of running a 1/2" trunk line and branching to those two fixtures. This trunk line will be about 12' long.

Think this plan is OK? (See below for part of the logic behind this plan.)

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Regarding buying the PEX tubing:
- Running a 3/4" line from the water heater to the manifold (~15') and a 3/4" trunk line from the manifold to the bathrooms (~58') will allow buying one 100' roll.

- Running a 1/2" trunk line from the manifold to the laundry room (~45') and a 1/2" trunk line from the manifold to the kitchen (~12') will allow buying one 100' roll.

Recalling that I'm only replacing the hot water lines, I think this will be the most economical plan without any negatives. If anyone sees a negative, please let me know so I can adjust my materials list accordingly.

Thanks for the help,
HomeRepairGuy


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## rjniles (Feb 5, 2007)

For the cost of a little more tubing, I would not cheap out. I remember your earlier post- just doing the hot side and not the cold. still a big mistake IMHO. Thing about resale, what will a home inspector say? Probably less that $100 in material to do the cold side also. Almost the same amount of work.


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## Homerepairguy (Aug 1, 2010)

rjniles said:


> For the cost of a little more tubing, I would not cheap out. I remember your earlier post- just doing the hot side and not the cold. still a big mistake IMHO. Thing about resale, what will a home inspector say? Probably less that $100 in material to do the cold side also. Almost the same amount of work.


Ok, sounds logical. I'll replace the cold water lines too.

Regarding the sizes of the trunk PEX tubing run to the laundry room and kitchen, think the 1/2" size will be OK? Rarely would there be simultaneous use from the two fixtures in either location. 

Thanks!


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## huynh (Sep 8, 2010)

I am thinking of replacing my copper lines with PEX pipes as the copper lines have started leaking at many places. 

According to your above posts, I think that I can branch the main PEX line as the same as the present copper lines that I have. Is that correct?

Can I place the manifold in the crawlspace near the water pressure regulator or does it have to be near the water heater?

I am still trying to figure out how to replace parts of the copper lines that already stay inside the walls. Please would not mind to show me how to do it.


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## Homerepairguy (Aug 1, 2010)

Hi huynh,

Not sure if your questions were directed to me or rjniles but I’ll tell you what I’ve learned and decided to do so far.

>> According to your above posts, I think that I can branch the main PEX line as the same as the present copper lines that I have. Is that correct? <<

Yes, that would be the “trunk and branch” system which is the system I’ll be using. I’ve changed my design though. I’ve decided to use all 3/4” PEX lines to our kitchen, back-to-back bathrooms and laundry room as trunk lines. The reason is that the inside diameter of PEX tubing and fittings are smaller than the equivalent copper lines. So running 1/2” PEX lines as trunk lines would be too marginal for me.

>> Can I place the manifold in the crawlspace near the water pressure regulator or does it have to be near the water heater? <<

I think folks would have to see a drawing of your setup to comment on the location of your manifold. 

I’m going to run a 15’ PEX line from our water heater in the carport to two “T” fittings outside of our house. Two “T” fittings will give me 3 outlets which is all I need for our hot water lines. Reason I’ll be using two “T” fittings instead of a manifold is that I haven’t been able to find a Wirsbo/Uponer manifold that has 3/4” outlets.

Also, the “T” fittings will be outside of the house so in case they ever leak, they won’t result in water damage in the house. All PEX lines will have insulation or be boxed to shield them from any direct or indirect sunlight. Either type of light is detrimental to PEX tubing. There will be an access panel at the “T” fittings for future inspection and any repairs if necessary. There won't be any PEX joints in the attic so zero chance of a joint leaking in the attic.

>> I am still trying to figure out how to replace parts of the copper lines that already stay inside the walls. Please would not mind to show me how to do it. <<

I can tell you how the one PEX installation that I saw personally is hooked up. This installation was a “Home Run” system. A Home Run system has one very large manifold with a lot of outlets and each outlet feeds one fixture. The PEX lines to each fixture just came out of the walls and connected directly to their respective fixtures. There were no valves at the fixtures. All valves were on the manifold. For basin or sink fixtures that were hard to reach, there were 3/8” copper tubing coming down from the fixtures. The 1/2” PEX tubing was joined to the copper tubing using copper to PEX adapters. 5/8” PEX was run from the manifold to the bathtub/shower fixtures.

In your case, I would suspect that your 3/4” trunk line to each location would have a remote manifold with 1/2” outlets to the fixtures. For a bathroom, the remote manifold might have 3/4” in and out on the main copper tube with 1/2” outlets. The 1/2” outlets would feed the basin and toilet while the 3/4” line would feed the tub/shower. Just my take as I’m learning how to install PEX just like you though I’ve done a ton of research so far. 

Finally, I’ve decided to use the Wirsbo/Uponer PEX system since I think the expansion method of fitting connections is more foolproof than the crimp method. Also the fittings for this system have a larger inside diameter than the fittings for the crimp system so less restriction to water flow. The Wirsbo/Uponer expansion tool is very expensive but I’m going to just bite the bullet and buy it. One other consideration is that ALL tubing, fittings and expansion rings will be Wirsbo/Uponer so there will not be any compatibility problems at the fittings. Leak proof joints for the long haul is my most driving force.


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## huynh (Sep 8, 2010)

Thank you, Homerepairguy!

You all know more than I do. My questions are to all of you. Any suggestions and comments are big lessons to me and are greatly appreciated!

So, you leave the copper parts that are already inside the walls and to the faucets. I just talked to the guy at Lowes. He said the same thing. He said that the copper parts that are going straight up rarely have problems. The horizontal parts of the copper lines have more problems with corrosion or leaking. He said I could use PEX for the horizontal lines and connect to the straight up copper lines.

I do not have a good location for the manifolds. The main line going inside the house from the crawlspace. I do not want to install the manifold down there. In case something went wrong, my crawlspace would become a pond! 

I will take time to see how I can do it, and I am going to do it soon! Can I use the PEX without any manifold?


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## Homerepairguy (Aug 1, 2010)

>>Thank you, Homerepairguy!
So, you leave the copper parts that are already inside the walls and to the faucets. I just talked to the guy at Lowes. He said the same thing. He said that the copper parts that are going straight up rarely have problems. The horizontal parts of the copper lines have more problems with corrosion or leaking. He said I could use PEX for the horizontal lines and connect to the straight up copper lines.<<

Welcome! Just remember that I've never installed a PEX system and anything I post is best knowledge at the time, subject to change. 

That's exactly how I'm going to install my PEX hot water lines. I'll cut the 3/4" copper hot water pipe coming up through the concrete slab and connect the 3/4" PEX to the cut end. I have to do this more as a sense of urgency since our copper hot water pipe has a slow leak under the slab. I'll build an access panel at the PEX to copper joint at each location and reassemble the walls with screws so I can 1) easily inspect the PEX to copper joint periodically and 2) replace all of the copper in the double walls later if necessary.

>> I do not have a good location for the manifolds. The main line going inside the house from the crawlspace. I do not want to install the manifold down there. In case something went wrong, my crawlspace would become a pond!  <<

Good move. Recommend putting your manifold where any leaks, or heaven forbid a tubing blowing off, will not cause water damage in your home. If in the garage, it would be a lot better to flood the garage floor and have the water run out to the street due to the slope of the garage floor. I'm even going to put a screened vent at the bottom of the box covering my two "T" fittings pseudo manifold to allow water to drain out of it should a leak occur. Water will go on my carport's floor, down the driveway. I think the best way to install PEX is to try to put any joints where a leak or tubing blow off will allow the water to flow out with minimal damage to the home. Again, "no joints in the attic!".

>>I will take time to see how I can do it, and I am going to do it soon! Can I use the PEX without any manifold? <<

I'm not using a manifold. As mentioned, I'll just use two 3/4" "T" fittings which will provide three 3/4" outlets to my three locations. No valve at the "T" fittings so all of the valves will be at the existing fixtures. If there's a leak in the hot water lines, I'll shut the water off using the ball valve going into the water heater.

Ideally, there would be a ball valve for each trunk line. That would allow shutting only one trunk down in case of a problem. I decided that for my particular installation it would be too difficult to bring the PEX tubings down to working level to install ball valves and back up to the attic with all of the 90 degree bends which is why I'm doing it as I described. I live in an area that never gets down to freezing so that's not a concern for my PEX tubing in the attic. Your milage may vary.


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## acerunner (Dec 16, 2009)

a plumber once told me that you can run 3/8" pex to all fixtures in a homerun manifold configuration. Not sure if that's allowed by code though. The idea is that pex flow better so 3/8" would perform just as well as 1/2" copper. And also, this reduces the volume of cooled water in the hot lines to have to flush out when you turn on hot water, thus reducing the effect of cold water sandwich.

I've never tried this, so don't know for sure, but it makes logical sense. Food for thought...


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## rjniles (Feb 5, 2007)

acerunner said:


> a plumber once told me that you can run 3/8" pex to all fixtures in a homerun manifold configuration. Not sure if that's allowed by code though. The idea is that pex flow better so 3/8" would perform just as well as 1/2" copper. And also, this reduces the volume of cooled water in the hot lines to have to flush out when you turn on hot water, thus reducing the effect of cold water sandwich.
> 
> I've never tried this, so don't know for sure, but it makes logical sense. Food for thought...




3/8 is fine if you are using home runs to a larger supply or a manifold. Think of this- what size is the riser from the stop valve under the sink? Answer 3/8"


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## Homerepairguy (Aug 1, 2010)

acerunner said:


> a plumber once told me that you can run 3/8" pex to all fixtures in a homerun manifold configuration. Not sure if that's allowed by code though. The idea is that pex flow better so 3/8" would perform just as well as 1/2" copper. And also, this reduces the volume of cooled water in the hot lines to have to flush out when you turn on hot water, thus reducing the effect of cold water sandwich.


I saw posts to that effect during my research. After much thought I don't think I would use PEX tubing smaller than 5/8" in a homerun system to the bathtub. 1/2" tubing to the other fixtures should be fine but I wouldn't use 3/8" tubing from the manifold. The inside diameter of 1/2" crimp type pex fittings is 3/8". The ID of 3/8" crimp type pex fittings would be smaller yet. I would prefer to lower the pressure reducer setting using 1/2" PEX lines rather than need to boost it for 3/8" PEX lines (if necessary). Lower water pressure equals less strain on the joints, less vibration shock on turn on/off and less noise when water is running.

My wife only takes baths so I'm running 3/4" PEX trunk tubing to the bathrooms. She would be disappointed if the flow filling the tub using smaller PEX tubing is any slower than the flow using the existing 3/4" copper trunk lines. If it's faster she will be thrilled.

Thanks,
HomeRepairGuy


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## Homerepairguy (Aug 1, 2010)

Homerepairguy said:


> For folks who have 1/2" PEX tubing run to their bathtubs, have you wished it was 3/4" PEX?
> 
> I'm going to run 58 feet of PEX from a hot water manifold to our back-to-back bathrooms. Each bathroom has a basin and a tub/shower. Would you recommend running 3/4" PEX tubing or 1/2" tubing?


Just a follow up to my PEX installation. I replaced the 3/4" copper line under the slab to the bathrooms with 3/4" pex in the attic since the copper line had a slow leak under the slab. Used 3/4" Uponor Aquapex with expansion fittings and it's working perfectly. The water flow out of the tub spout is the same as the copper line. Thought I'd post this since I learned some things about working with PEX along the way.

PULLING 3/4" PEX THROUGH THE ATTIC:
The 3/4" Uponor aquapex tubing is much stiffer than I first imagined. I thought I'd have to uncoil the 100' roll in the sun before I started, to straighten it out. Learned that's not necessary. I left the coiled pex in the plastic wrapping that it came in. I uncoiled about 15' from the center of the coil and straightened the first 8' using a hair drier. Applying heat made the pex straighten all by itself due to the pex memory though I did help it a little. The first 15' being somewhat straight made pulling it a lot more manageable.

I just pulled the 3/4" pex tubing through the attic (on my belly since we have a very low pitch roof) while a friend uncoiled and fed the pex from outside of the house. To turn a corner I drilled two holes in the bottom of a 5 gallon bucket and screwed the bucket to a 1x6 lumber. Then I screwed the 1x6 lumber to the top of the ceiling joists. The bucket allowed pulling the pex 90 degrees to the bathroom's double wall. The uncoiled 3/4" pex just followed my pull path without any hitches. Very easy in fact.

REDOING AN EXPANSION FITTING:
The manual that came with the Uponor pex expansion tool said that joints can be redone by heating the expansion ring with a heat gun and then cutting it with a knife. Then heat the tip of the pex and pull it off the fitting. It says to NOT use a flame to heat the pex. I have a heat gun so that was not a problem. Suggest buying or borrowing a heat gun for any Uponor pex installation. --- On my first joint, I had to connect the pex to the brass "copper to pex" adapter in a confined space. When I pushed the pex on the fitting, it only went on part way and wouldn't move. I removed the pex using the instructions above and cut about 2" off the tip of the tubing. Installed the pex on the fitting again and this time it went on fully.

PLASTIC PEX HANGERS:
I used the plastic pex hangers that have two ears on them to mount them to the bottom of the rafters. At the 90 degree turn I used two plastic ties (the kind that police use as handcuffs except sold for pex use) and loosely hung the pex from the rafters and hip. This will allow the pex to expand and contract on both sides of the turn. If I had secured the pex throughout the turn I figured it would not allow expansion and contraction any where near as well. --- Used the plastic pex mounts where the pex went through a 2x4. This allows the pex to move without rubbing against the wood. --- Used the 3/4" pex mounts when running the pex along the side of one rafter and along a wall. Do not buy the universal type plastic mounts for 1/2" to 3/4" pex if installing 3/4" pex. They will press the 3/4" pex against the wood and smash the pex if secured too tightly. Buy ONLY the 3/4" mounts which hold the pex about 1/16" above the wood surface. ( EDIT: My initial impression was that the 3/4" mounts would hold the pex 1/16" off the wood surface but upon closer examination after the installation, the pex just touches the wood with no clearance. But the 3/4" mount does not smash the pex as the universal mount would have.)

SUMMARY:
The Uponor pex expansion connections are really easy to make. Buy an extra fitting and practice installing on that before doing the actual install. Once on properly, the joints are very solid and I don't see how they could possibly pop off the fittings (which was a concern I had prior to my installation). Just be sure to support the copper pipe and the pex so there is no sidewards strain on the fittings. I really like the comfort of not having to do the "go, no-go" test required for the crimp style fittings.

Hope this helps future, first time Uponor pex installers,
HRG


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