Our home has a large addition on it and i'm thinking of running newer lines throughout our original house that has copper. There are many bends at various points and some are starting leak (probably 40+ years old). The original part of the house would need 6 hot and 9 cold runs setup whereas the addition would need an additional 6 hot and 8 cold. There's two 3/4" main lines (one hot, one cold) that feeds the addition of CPVC. I'm curious if I switch over to use a home run PEX manifold setup just for our original house if that would cause a pressure drop on the addition side or pose any other problems. Additionally here's a rough diagram (excuse the resemblance to pre-school art) of what i'm looking to accomplish.

I realize too switching out the copper for PEX may pose an issue with the grounding of our house so that will be verified by an electrician unless anyone has any tips on confirming this.

plumbing diagram http://www.yukoncreative.com/remedy/wp-content/uploads/2014/08/plumb-diagram.png

1 Answer 1


That looks perfectly suitable. One additional thing you should be aware of, though - if your existing plumbing contains any yellow brass fittings, they really need to come out because of a chemical quirk of PEX; the zinc gets leached out of yellow brass, leaving behind only soft copper, and the fittings may either leak or plug solid. You can use RED brass, just not YELLOW brass.

The manifold should be one size larger than the pipe supplying it.

If there's any question at all about grounding, a solid ground rod can be driven... with the result of giving you a better ground than you ever had by grounding through copper pipe.

Like copper, PEX requires a 1/4" drop per foot (never install it level or wavy), and requires a drain at every low point so the house can be winterized if necessary.

Is there any particular reason for going with PEX instead of tending to leaky fittings as you find them? I suspect that those fittings were always leaky because they were never sweated together correctly in the first place. I ask this question because replumbing the entire house in PEX is really a large, expensive job... while replacing (or resweating) one fitting at a time is relatively cheap.

  • I'm curious as to why you would need to install copper or pex with a 1/4" per foot grade. Is there a code requirement for this. Winterization can be addressed by blowing out the lines with air if that is the concern.
    – pdd
    Aug 14, 2014 at 23:28
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    The use of air to winterize requires a HUGE amount of air delivery. Anything less will blow water only until the air has a path past any standing water in the pipe. I've seen an awful lot of burst plumbing that was "winterized" with an air compressor. ALWAYS provide a bleeder, or some other means of draining plumbing, at every lowest point. That's guaranteed to drain ALL the water out. Failure to drain ALL the water out can result in some major messes when the pipe freezes & bursts, then thaws, then the water gets turned back on. Yes, PEX will burst. Not the first time, usually, but it WILL. Aug 14, 2014 at 23:49
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    The need (and requirement) for winterizing provisions depends on your location, check with the local permit authority. Here in So. Cal. we don't have to and never do, except in the mountains. Aug 15, 2014 at 17:51

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