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Thread: Branching off water supply lines

  1. #1
    DIY Junior Member JMichael's Avatar
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    Default Branching off water supply lines

    We bought a dual sink vanity to replace the single sink vanity in our master bathroom. The supply lines and drains line up perfectly with the middle section of the vanity which is for the drawers, so everything needs to be moved. I'm not even going to bother with the drain lines and will have a professional take care of those, but I feel I can handle the supply lines if I can get a few questions resolved.

    Some info on the setting. The current piping is 1/2" galvanized steel and is run through a crawlspace of a one-story house. The master bathroom shares a wall with the guest bathroom.

    Here is an overhead diagram of the lines in the wall right now.



    There is a 2x8" joist running parallel to the hot water line blocking where I need to run the supply lines for the left sink. The dots represent vertical pipes. The one furthest to the right is for the toilet in the adjacent bathroom.....the other two are for the current sink in the master bathroom.

    It looks like it would be most feasible to unthread the pipe and elbow for the toilet supply line and extend off that line back to the left and branch off it for each of the new supply lines. For the hot water, I can take the vertical pipe and the short horizontal extension off and extend it. But to get back to the left sink, I'll need to have it do a u-turn. And, of course, all these new extended lines will need to cross over the current long horizontal runs of pipe which means one will be higher than the other and they will be close to each other. I don't know what best practices say about that.

    The quick and dirty option would be to just run one hot water and one cold water supply line up behind the right sink of the vanity and branch off of it with flexible pipe on the outside of the wall and run that pipe behind the vanity where there is about 4" of space behind the back of the drawers to the left sink. But that's about 3' of flexible pipe and, again, I don't know if that is viable.

    So any guidance on how to handle this situation would be appreciated.

  2. #2
    DIY Senior Member Fubar411's Avatar
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    How old is your house? What condition is the galvanized in?

    I'd just go with 3/4" copper and branch off to 1/2" for the fixtures. Going from one sink to two shouldn't require a lot more water, but if you have access, replacing might make sense.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Eventually, you'll probably need to replace ALL of the galvanized steel piping, so I wouldn't even consider modifying it with new galvanized. That pipe will rust out and eventually both leak and restrict the flow as the rust expands and fills the interior of the pipe until the whole thing becomes swiss cheese. As iron rusts, the resulting iron oxide is bigger, which means it exposes more of the iron to water, so it rusts. Get rid of the parts you can while you remodel.

    I'd go to a convenient place to transition to either copper or pex, and tear out as much as I could of the galvanized in the process.
    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 Junior Member JMichael's Avatar
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    Quote Originally Posted by Fubar411 View Post
    How old is your house? What condition is the galvanized in?

    I'd just go with 3/4" copper and branch off to 1/2" for the fixtures. Going from one sink to two shouldn't require a lot more water, but if you have access, replacing might make sense.
    The galvanized all is in excellent condition. No leaks and no rust visible anywhere. The house is 50 years old.

    Where would you branch off?

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    DIY Junior Member JMichael's Avatar
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    I guess the main question I have is, can pipes run up and over each other and, if so, what is the recommended method....clearance, etc.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Water do do flips and loops if needed.
    Waste lines need 1/4" per foot grade on them.
    That's why the Journeyman runs waste and the apprentice runs the copper or PEX.

    Waste and vents first, and then the water supply.
    Last edited by Terry; 08-26-2010 at 09:30 AM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    You won't know the state of the galvanized until you open it up...it rusts from the INSIDE out...trash what you can while remodeling.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Test, Don't Guess! cacher_chick's Avatar
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    Quote Originally Posted by jadnashua View Post
    You won't know the state of the galvanized until you open it up...it rusts from the INSIDE out...trash what you can while remodeling.
    Jim, one thing you need to remember is that water is different everywhere.

    I too have 50 year old galvanized pipes and started replacing them until I found the first 20 feet that I cut out was just as clean on the inside as the day it was new. I've seen restricted pipes in other houses, but it doesn't mean that every location will suffer from the same problem.

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    DIY Junior Member JMichael's Avatar
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    Quote Originally Posted by Terry View Post
    Water do do flips and loops if needed.
    Waste lines need 1/4" per foot grade on them.
    That's why the Journeyman runs waste and the apprentice runs the copper or PEX.
    Thank you.

    With that being the case, I may switch to PEX. My plan would be to replace the current vertical pipes with T connectors branching off to two PEX pipes that are each routed to their destination. I'll add an extra 6' worth of PEX for each run that I will be able to use to run to a manifold further down the supply line when I replumb some day....in the meantime I'll fashion it into a loop.

    So about PEX. I saw a video where some guy used a huge tool to slide what looked like a hose end adapter onto a PEX tube. But all I've seen for sale are crimp style adapters and tools. Is crimping alright to use and, if so, is there anything I can do to give myself some extra peace of mind like use two rings or something?

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    There are three generally available ways to attach pex to fittings: crimp, expansion, or clinch. The last is probably the most expensive and uses specialized fittings that insert into and around the pipe - they just push on, no tools (well, there is a forth, but they are more expensive). An example of them is the Sharkbite fittings Acme. Uphonor uses the expansion method. Pex has memory. They use a tool to expand the pipe, then the fitting is inserted into the now larger ID pipe, and then the pipe collapes to its original size, and clamps the fitting in place. to give it even more strength, they use a band of pex that fits over the end, and you expand both before inserting the fitting. Because you expand the pipe, the fitting ID is also larger, and has less restrictions. The crimp fittings require the proper tool, and some require you use a go/no-go gauge tool to verify it actually got crimped properly. Because it is pushed into the unexpanded tubing, it has to be smaller ID to fit and have enough strength. The crimp style is the most commonly available in the big box stores. If you place and crimp the ring properly, I don't see an advantage to use two.

    Pex can be made using three methods, labeled -a, b, or c. Quality of manufacture is important, and any can work. Type -a is the most flexible and can be bent into the smallest radius. it is also the only one that can be restored to full capacity if you get the tubing crimped while installing. On the others, if you crimp it, you either replace, or cut out the section and patch it back together. Type a, you heat it up with a heat gun, and it restores itself to the original shape and strength.
    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 Junior Member JMichael's Avatar
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    If I set up a remote manifold system, would 1/2" PEX be fine for supplying bathroom fixtures?

    Are there any cons to going with 3/4" PEX instead of 1/2" PEX?
    Last edited by JMichael; 08-25-2010 at 10:28 PM.

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    DIY Senior Member Hairyhosebib's Avatar
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    Install the new drainage pipe first. Then run the water lines. As far as I'm concerned, getting the water away properly is more important than getting water to the faucet. Drain is gravity, supplies are under pressure.

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    DIY Junior Member JMichael's Avatar
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    Quote Originally Posted by Hairyhosebib View Post
    Install the new drainage pipe first. Then run the water lines. As far as I'm concerned, getting the water away properly is more important than getting water to the faucet. Drain is gravity, supplies are under pressure.
    The current supply lines are in the way and need to go first. I'll be putting in PEX with lots of slack, so the new pipes shouldn't be in the way. I'll keep that in mind though and will make sure I leave them room for the drains.

  14. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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    Often, they run 3/4" to the area, then branch off to the individual items using 1/2". 3/4" to the tub/shower might be best, but the toilet and sink can easily be serviced with 1/2". A 3/4" pex line will have about the same flow as 1/2" copper. If there is only a shower, and it only has one head, 1/2" should be okay. 3/4" to the tub, will allow it to fill faster (you can reduce it to a 1/2" valve).

    The disadvantage of larger supply pipes is that if you don't run hot for awhile, there's more cold water than needs to be purged than if the pipes are smaller. this is where recirculation can really help. You might want to consider a return line, even if you don't install recirculation now, it would be there if you eventually do. But, if the supply to the bathroom is too small, you could have flow problems or pressure changes in the shower if someone else uses say the toilet or sink while you are showering.
    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 Junior Member JMichael's Avatar
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    Cool. I think I'm set. I understand PEX will virtually eliminate water hammer sounds, but the water hammer effect will still be there, correct? I was going to end the PEX at drop elbows, but if I need water hammer arrestors at each end point, am I better off using a T connection at the stub out and continuing up another 10 inches to create an arrestor?

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