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Thread: Never used PEX Before

  1. #1
    DIY Member M3's Avatar
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    Default Never used PEX Before

    I have only plumbed with copper in the past but I am now planning a spa shower including the normal shower head, 4 body sprays, and a handheld... It seems that plumbing this with copper would be very tedious but I haven't used PEX before. This area will NOT be visible or accessible when finished. Is PEX OK to use in this instance, or should I stick with copper?

    With PEX I like the fact that I would have to solder near all the Moen controls... Also, I can rent a crimper so the cost would be minimal vs copper.

    Should I be concerned with using PEX?

    Thanks.

  2. #2
    DIY Member philp's Avatar
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    PEX is great in most circumstances. I ran PEX for a basement bathroom and my washer and it was fantastic as it is somewhat flexible so if my joist holes were slightly off it was very forgiving (copper would not allow this) or if my measurements were out 1/4" it made no difference - try that with copper. Plus it cuts down on joints as I could do a wide angle bend rather than L's and if I needed a 90 degree turn it was easy - no worrying about starting a fire trying to solder an L between joists. If you make a mistake it is easy to correct. If you need to T into it later it is simple - try T'ing into a long run of copper in a tight space. Nearly all the accessories for copper are available for PEX - though not every store stocks them.

    The downside is anchoring it where it joins a fitting. For my washer it was easy as there is a fitting that can be screwed to a stud but for the shower I had to add copper prior to the valve and head so these fittings would be solidly anchored. The body sprays will probably need copper for the same reason but the special pressure balancing plumbing behind these could be PEX. Or maybe your fittings don't have these problems. For the toilet and vanity, PEX was fine as there are special supports you can use (or just clamp to a stud) and it doesn't matter if there is slight give in these.

    Hope that helps - I'm planning to replace much of the copper as I redo other bathrooms and kitchen. You can cut PEX with a sharp blade but one of the special cutters is worth the investment if you have a lot to do.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    For maximum flow, copper has a significantly larger ID. If this is a tub/shower, the use of pex, at least to the tub spout, may create enough restriction so that water backs up and dribbles out the showerheads before the diverter is turned on. If there are multiple heads, I think you want to use copper. If there is a tub spout, at least run copper to it. Otherwise, pex would work. I've had work done on my home using pex. They used, and I prefer the Uphonon system that doesn't use crimp rings. Pex has a memory, so is always trying to go back to its original size and shape. A crimp type system restricts the flow, then to make the connection compresses it between some ridges to make the seal. It always wants to expand and the fitting reduces the max flow because of restrictions. Uphonor's system uses an expansion tool and the fitting has a larger ID so it flows better. It is always trying to make a tighter connection, not a looser one.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member M3's Avatar
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    Quote Originally Posted by jadnashua View Post
    For maximum flow, copper has a significantly larger ID. .
    Thank you for bringing that to my attention! I did compare standard PEX and copper sold by HD and the PEX 3/4" fittings have virtually the same ID as 1/2" copper!!! I would have thought that would be a violation of some code... talk about misleading... I'll look into Uphonor.

    Still lots to think of: There is no tub on this new shower setup but potentially 6 water outlets that can be utilized at one time (knowing my wife she'll use 5 or all six at once). The body sprays need a 1/2" but with runnng 4 at once I was going run the loop with 3/4", and the main supply to the shower has 3/4" copper.

    One other question: I saw that Moen recommends a "booster pump" for low-pressure or private well systems. Is this a good idea? I have a well, but it can maintain 50 psi while filling a tub, and running a shower, sink and toilet at the same time; and if I add another tub and two sinks it drops to 45 psi. My thought is that if the well can't keep up, a booster isn't gonna help.... Am I correct?

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    A booster works for perpetually low pressure, like at the end of a municipal line or on top of a hill. If you need more pressure, bumping the pump pressure switch up may be better. A booster pump would only work if your flow from the main pump and any water you have stored can keep up, otherwise, it would be like sucking from a dry hole. 50# should be okay, but if you want to run all 6 heads at the same time, you will need both a big water heater, a 3/4" supply valve, and supply lines, or you will be disappointed.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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