replacing galvanized water pipes with pex

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by fhorta, Feb 23, 2013.

  1. fhorta

    fhorta New Member

    Messages:
    14
    Location:
    bakersfield
    Hello,

    Just wanted some general guidance/info. My home currently has the old galvanized pipes. This is a problem because the water pressure in the house is weak, and much weaker when two faucets turn kn at the same time. Even if the toilet water is refilling after flushing, have to wait till its done before turning on shower cuz the shower barely pours a drip. A private contractor came out and indicated its the old piping. I have heard that pex ismuch easier to install and arguably a better choice than copper. My home is on raised foundation and have crawling space and can reach my pipes. My question: what kind of pex would be the best option? What size pex should i use. I think the existing pipes are the stamdard 1" or 3/4"..i know the home was built in 40's. Gone try to do this on my own just want to be as prepared and informed as possible..btw, the water pressure outside the house is fine. Thanks for any tips, advice, sugestions.
    Last edited: Feb 23, 2013
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    PEX is NOT "arguably better" than copper. Rodents can chew it , etc. It is cheaper to purchase, and less labor to install.
    Size-wise, comparing nominal to nominal , PEX is SMALLER, so you need to always be one nominal size UP. Any 3/4" copper is replaced by 1" PEX, 1/2" copper replaced by 3/4" PEX
  3. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    I think "arguably" was the appropriate word here... you can argue both ways about it.

    Anyway, I'm a pex fan, but it has some caveats. It is slightly smaller internal diameter, this can be a problem. Since I always install a "home run" system, this point is completely moot. That's where you feed a manifold with a large supply line, then use typically 1/2" pex lines from that manifold to each individual fixture. This eliminates any flow rate issues, b/c the lines aren't "sharing" water between fixtures. 1/2" is more than enough for any regular fixture, with the exception of some high flow shower systems, so you'll never have issues.

    It has to be protected from direct sunlight. It can be chewed by rodents, though I haven't heard too many stories of such (why would they want to chew plastic other than to get through it to something they want on the other side, which there isn't anything). Pex is more easily punctured by glancing nails and the like than copper.

    Copper is much more likely to lose flow rate over time due to corrosion. Its much more likely to burst if allowed to freeze. It has far more potential leak points b/c of far more fittings. Its far more expensive to buy and to install. It can't be shifted out of the way for later work, you have to cut it apart. Actual flow rate in real systems is much lower than spec due to all the fittings, which a homerun pex system doesn't have (only a connection at manifold and then at fixture).

    There's good and bad to both, and both have their place. My own home is mostly pex, but I use copper manifolds and my heating system piping between water heater and pumps and all those lines are all copper. Radiant floor lines and runouts to all fixtures are pex.

    If you're doing it yourself, the best system is the copper crimp rings with plastic or brass fittings. The expansion system by wirsbo and others is what most pro plumbers use, but I don't generally advise it for DIYers - equipment costs, etc. The main advantage to that system is the fittings have a larger I.D. than the crimp ring fittings, so the flow rate is not reduced as much. Again, with a homerun system's very few fittings, this is a minor concern.

    Your system is likely a 3/4" trunk with 1/2" branches setup. This is pretty standard for ridgid pipe systems in homes. If you don't want to do the homerun system in pex, I'd do a 1" main trunk line, with 1/2" lines to fixtures. Do a separate line for each fixture. If you want to group a few fixtures onto one runout from the main trunk, run it out in 3/4" pex, with 1/2" lines off that to each fixture.

    The homerun system will cost you more time and a good bit more piping, but will use a lot less fittings and will greatly improve the balance of your system (when you flush toilet, shower shouldn't go hot, etc). It can't fix very low pressure problems, but it will do the best that is possible in your home given the pressure you have.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    quote;why would they want to chew plastic other than to get through it to something they want on the other side, which there isn't anything

    There is WATER on the other side, which is what they are looking for. They used to do the same thing to lead water pipes. i also had one chew through a plastic gas pipe, but that was because it was in the way of his burrowing.

    quote; Copper is much more likely to lose flow rate over time due to corrosion

    That is trying to create hysteria. Copper does NOT "corrode", it develops a patina, but that does not restrict the flow rate.
  5. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,349
    Location:
    Yakima WA
    I have no scientific data to prove this, but it seems logical to me that water pressure is bound to weaken flexible plastic hose, AKA PEX, over a period of time. Yes, copper will break if frozen, but for gosh sakes, install where it will be protected from extreme temperature.
  6. fhorta

    fhorta New Member

    Messages:
    14
    Location:
    bakersfield
    Thanks to all for replies. I reside in central california, so extreme cold weather i dont think would be problem and pex would be under house so protected from sun. A local plumber (licensed) is quoting me at $500 for pex and $1000 for copper. I have two bathrooms with two showers, bathtub in one bathroom, one kitchen sink andof course two bathroom sinks oh, and two toilets. The square footage for dwelling area is about 2700. Does price sound reasonable, or more so on the "sweet deal" side...? Thanks again
  7. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,349
    Location:
    Yakima WA
    If cheap is your goal, then PEX is your choice.
  8. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    It is nothing of the such. Copper is much better than say cast iron in this regard, at resisting corrosion, but it does happen. I see it with my own two eyes quite frequently when removing the original copper tubing in these old Pittsburgh houses. The ID of the copper lines has shrunk (very slightly, albeit), but more importantly, its no longer smooth walled. This creates a lot of flow restriction.

    I have no interest in creating hysteria. As I said, I use copper for some things too, and they both have their place. I've replaced trunk and branch copper systems with home run pex systems and seen and felt the dramatic increase in flow rate and pressure balance through the system. Most of that is b/c trunk and branch is a far inferior performing system to a homerun system, and you'd likely see similar results with a copper homerun system. But I sure ain't paying for that to be installed.

    Gary, expansion and contraction is proven to weaken metal over time. Copper expands and contracts quite a bit as hot water passes through it. This is likely why I seem to have to fix the hot water lines far more often in these old houses than the cold lines.

    As I've said, there's good and bad to both systems. I've weighed out all the opinions and objections to both, and fallen in the pex camp as a preference. But really it ought to be installed in a homerun system to take advantage of its best qualities.

    Is that price for the pex install for a trunk and branch system, with same size piping you have now? If so, its not worth it in my opinion. If its a homerun system, its a good price. There's a lot of work and piping involved in that system, I'd be very surprised if you got it for significantly different price than a trunk and branch copper system.
  9. fhorta

    fhorta New Member

    Messages:
    14
    Location:
    bakersfield
    Wow! I never heard ofa homerun system before compared to a trunk and branch system. Had to reread post couple of times; makes sense. He didnt specify what installation but i will definitely bring it up. This is why i wanted to ask you guys to be somewhat "armed" when talking about work to be done and price..ill post back what he says.
  10. fhorta

    fhorta New Member

    Messages:
    14
    Location:
    bakersfield
    Plumber quoted
    Me at $2000 for doing all the repiping with pex. He said he would use 1" trunk then 3/4" b ranches and 1/2" to the fixtures. So he will replace washer, two showe rs, two toilets, two bathroom sinks, one kitchen sink, one bathtub, and of course both hot and cold on all. The dwelling are a is about 2700 sq ft. So from where the water heater is to the last fixture is in the house is about 35 ft. in distance. How does quote sound? Big difference from $500 but he thought i was just wanting to replace showers..
  11. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    $2k for a trunk and branch pex system seems high, but that is also hard to say without seeing what obstacles he's dealing with for running the piping.

    If you do a pex trunk and branch, those sizes are appropriate.

    If you're handy, you could probably do a lot of this work yourself (with a helper to feed pipe). If you wanted a homerun system, for example, and you drilled the holes to get the pipes to where they need to go (read up on proper places to drill through structural members - its not complicated, but important), and pulled 1/2" pex cold lines to one spot in your basement between your main line and the water heater, and hot lines from fixtures to one spot near your water heater, then the plumber could come in and just run the main line, manifolds, water heater connections, connections at fixtures, etc. This would probably save you a lot of money overall, and you'd have a much better system than the trunk and branch he wants to install. Just make sure to leave an extra couple feet of pipe on each run at each end, so that he can cut them to the length he needs them.

    You could probably do most of your part of this work without turning off the water.

    Just a thought, but this from someone who likes to do everything himself :)
  12. fhorta

    fhorta New Member

    Messages:
    14
    Location:
    bakersfield
    yeah, i would definitely give it a shot if i had the time. about drilling holes though, if i were to do it myself, as i had considered, i was thinking of just using same holes already there from existing pipes. in other words, i was just thinking of replacing pex for pipe, following same pattern of existing pipe and just replacing with pex, pipe for pipe.. was i way off on strategy??
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,006
    Location:
    New England
    You may need to enlarge the holes of the existing piping if you want to maintain the same flow, since where there's 1/2" copper, you may want to install 3/4" pex. THen, to get all of that copper out of there, you'll be making a lot of cuts. Save it all, though, as it has a good recycling value. You may need to sign a waiver and provide ID, since copper thieves operations are in high gear...don't leave any of it sitting outside or it'll likely be gone!
  14. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    Yeah, if your holes aren't significantly oversized for the existing pipe, you will need to drill them out larger in order to properly size the pex main lines. the 1/2" runouts to individual fixtures you could probably reuse.

    I usually run most of the piping, have all the connections made, etc before I disconnect the old system if possible. Just more convenient for use, but it does require more drilling, etc.

    But since I'm always taking out trunk/branch and replacing with home run, i had to do a ton of drilling anyway.

    Copper makes a pretty penny (literally and figuratively) at the scrapyard. Unfortunately you said you have galvanized pipe, which is a lot less desireable, and a LOT harder to get out when its been drilled through joists. I'd abandon it in place probably except for where it goes up to the fixture. Run all your new lines and leave them hanging there, when you're ready, drain system, just cut out the risers to the fixtures, and run pex lines up through those holes.
  15. fhorta

    fhorta New Member

    Messages:
    14
    Location:
    bakersfield
    Ok, that sounds more how i was planning. Im a bit confused still about the drilling. I get the need to have to enlarge the fixture hole, but that wouold be it i think
    The existing piping does not go through anything under the house..it just hangs via bracket which is screwed in on wooden boards under house..
  16. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    ok, i prefer to drill my pipes through the joists, but if its code compliant where you are, in your type of construction to just clip them to the joists, then that will make it much faster/easier. It also makes it even easier to run all your pex lines ahead of time, then do the switch over after. It also makes the homerun system much easier to install, you can just run a bunch of cold water lines right next to each other with one big clip/strap holding the whole bunch up together. I generally prefer to keep my hots separate from each other and insulate them individually, this makes the hot water get to each fixture faster with less heat loss to the air and the other dormant hot pipes.

    You could have the entire system run, clipped up, etc other than the main line to manifold connection and the individual fixtures (just leave extra pipe hanging under house until ready to swap out the galvanized), and switch the whole system over pretty quickly with minimal down time. And this shouldn't cost that much more than the trunk and branch system - a lot more pipe, but pipe is cheap. A lot less fittings, which are less cheap and a bit of labor savings.
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