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Old 11-15-2010, 01:19 PM   #1
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Copper to pex manifold on bathroom remodel


I am not a plumber so any additional advice you would like to give is appreciated. I am in the middle of a bathroom remodel and am relocating the tub and expanding the shower adding a couple of shower heads, etc. In the crawl space under the bathroom there is a 3/4 inch hot copper line and a 3/4 inch cold copper line. From the 3/4 inch line the toilet, old shower, sinks, and tub are all plumbed with 1/2 inch copper lines that T off with soldering on the joints, all looked pretty good, but I had to cut out the shower and tub lines as those fixtures are being relocated. I capped the lines I cut for now with the sharkbite push on end cap (I know some people hate sharkbite, but it is just a temporary fix).

My plan is to cut the 3/4 inch main lines and add a pex manifold with 8 or so hot connections and 8 or so cold connections. My thought is to run pex from the manifold to each plumbing fixture (bath, sink 1, sink 2, shower head 1, shower head 2, shower hand wand, and toilet). I have attached an illustration of what I am thinking about doing and I have a couple of questions:


1. Is using a pex manifold and pex line a good idea? I like it and most the folks I have spoken with speak highly of it.
2. Does running 1/2 inch lines from the manifold to each fixture provide enough water volume and pressure? I haven't tested the pressure in my line yet, but prior to demolition the shower had one shower head and great pressure.
3. When putting three sources of water in one shower I have seen people put "loops" in the plumbing in order to prevent pressure drops and temperature changes when the second shower head is turned on. Does the manifold eliminate the need to do this since each head and the wand has both lines going all the way back to the manifold?
4. Any recommendation on a good two shower head one wand fixture? I have been looking at Moen... I usually like their fixtures, but am unsure of which one to purchase.



Thanks for any advice you can provide.
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Copper to pex manifold on bathroom remodel-bath-copy.jpg  

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Old 11-15-2010, 02:47 PM   #2
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Copper to pex manifold on bathroom remodel


I have limited experience, but I love pex for retrofits b/c its quick and flexible.
I know of no manifold that accept a sweat copper connection. If it wereme, i'd use a sharkbite to covert from copper to pex, then attach the manifold.

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Old 11-15-2010, 02:54 PM   #3
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Copper to pex manifold on bathroom remodel


I have limited experience, but I love pex for retrofits b/c its quick and flexible.
I know of no manifold that accept a sweat copper connection. If it wereme, i'd use a sharkbite to covert from copper to pex, then attach the manifold.
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Old 11-15-2010, 04:25 PM   #4
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Copper to pex manifold on bathroom remodel


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Originally Posted by jpeake View Post
1. Is using a pex manifold and pex line a good idea? I like it and most the folks I have spoken with speak highly of it.

2. Does running 1/2 inch lines from the manifold to each fixture provide enough water volume and pressure? I haven't tested the pressure in my line yet, but prior to demolition the shower had one shower head and great pressure.

3. When putting three sources of water in one shower I have seen people put "loops" in the plumbing in order to prevent pressure drops and temperature changes when the second shower head is turned on. Does the manifold eliminate the need to do this since each head and the wand has both lines going all the way back to the manifold?
Disclaimer: I'm not a plumber either and am just starting a pex replacement for our copper lines. Never used pex before but have done a TON of research. All of my responses below may or may not meet code in your area.

1. I don't see anything wrong with installing a 3/4" copper to multiple 1/2" pex manifold. It's effectively a trunk and branch configuration which is common for pex.

2. Realize that 1/2" pex "crimp or cinch" fittings have an ID of about 3/8". This is smaller than the 1/2" ID of 1/2" copper lines. Running 1/2" pex to basins, toilets and showers will be fine. You might want to do more research in running 1/2" pex to your tub though. Probably depends on how long folks are willing to wait to fill the tub if folks take baths. My nephew's home is all PEX and the builder used 5/8" pex to the tubs in a homerun system. --- The ID of the Wirsbo/Uponer expansion fittings is larger so allows more water flow. I don't know how much of a difference it actually makes though.

3. "Does the manifold eliminate the need to do this since each head and the wand has both lines going all the way back to the manifold?" --- Yes because it is effectively like a homerun or remote manifold installation which are common using pex.

HRG

Last edited by Homerepairguy; 11-15-2010 at 04:33 PM.
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Old 11-16-2010, 02:39 PM   #5
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Copper to pex manifold on bathroom remodel


I appreciate the reply and advice offered so far. I went to a local plumbing store and looked at one of the Pex manifolds today, I found one with six hots and eight colds which I think will work. All of the outlets on the manifold I looked at are 1/2 inch and I don't think it would work to use an adapter to step up from a 1/2 inch line to a 5/8 inch line in order to run it to the tub, I think the 1/2 inch choke point on the manifold would reduce volume. Am I right in thinking that the way to do this is to put in a 3/4 inch tee on the 3/4 inch copper line, then an adapter to the 5/8 inch pex and then run that to the tub. That will provide increased volume to the tub and I can hook everything else in the bathroom up to the 1/2 inch outlets on the manifold. What do you guys think? Is that an acceptable way to do plumb everything? Thanks in advance.
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Old 11-16-2010, 03:59 PM   #6
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Copper to pex manifold on bathroom remodel


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Originally Posted by jpeake View Post
I appreciate the reply and advice offered so far. I went to a local plumbing store and looked at one of the Pex manifolds today, I found one with six hots and eight colds which I think will work. All of the outlets on the manifold I looked at are 1/2 inch and I don't think it would work to use an adapter to step up from a 1/2 inch line to a 5/8 inch line in order to run it to the tub, I think the 1/2 inch choke point on the manifold would reduce volume. Am I right in thinking that the way to do this is to put in a 3/4 inch tee on the 3/4 inch copper line, then an adapter to the 5/8 inch pex and then run that to the tub. That will provide increased volume to the tub and I can hook everything else in the bathroom up to the 1/2 inch outlets on the manifold. What do you guys think? Is that an acceptable way to do plumb everything? Thanks in advance.
Typical "trunk and branch" pex systems that I've seen while researching, run 3/4" tubing to each location. A location could be back-to-back bathrooms, or the kitchen, or the laundry room. Then a remote manifold at the location converts the 3/4" to 1/2" outlets to feed the basins, toilets, showers, etc. The remote manifold can be a "through" type with 3/4" inlet and 3/4" outlet. If it's a copper remote manifold, 3/4" copper to pex adapters would have to be installed on the copper manifold. --- I myself wonder if 3/4' trunk lines are really necessary for the kitchen and laundry room since I discovered that our existing copper lines run 3/4" to the bathrooms but 1/2" to the kitchen and laundry room. I'll definitely run a 3/4" trunk line to our bathrooms though.

The 3/4" outlet from a remote manifold can feed the bathtubs. However, this is where it gets vague. I don't know if the 3/4" outlet from the remote manifold just goes to a 3/4" "T" fitting and 3/4" feeds the bathtubs, or if there is a 3/4" to 5/8" fitting to send 5/8" to the bathtubs.

On my nephew's homerun pex system, the manifold had 5/8" pex outlets and 1/2" pex outlets. The 5/8" pex outlets feed the bathtubs and 1/2" outlets feed everything else.

HRG


Last edited by Homerepairguy; 11-16-2010 at 04:06 PM.
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