need some advice on pipe size (soon)

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by black hawk, May 25, 2006.

  1. black hawk

    black hawk New Member

    Messages:
    4
    I am in process of a total replumb job ( hurricane rebuild) . I am coming into the house with a 3/4 feed line, question is, once I start making runs,should I continue the 3/4" cpvc, and use 1/2" droplines to fixtures, or just use 1/2" for the wholeworks??

    Look forward to hearing from ya's

    Steve

    PS this looks like a terrific forum
  2. Kristi

    Kristi Tradesman Plumber

    Messages:
    176
    Location:
    Vancouver, BC
    take 3/4" as far as you can, run the branches to individual fixtures in 1/2".

    If you want to do an outstanding job, you could take this opportunity to run a 3/4 line to the mechanical room, create a header loop with the 3/4 then branch each fixture off from there with an isolating valve and 1/2" to supply them (don't forget to label them!) - this would balance the system and not rob one fixtures water from another. One header loop for hot, one for cold.

    ~k~
  3. black hawk

    black hawk New Member

    Messages:
    4
    you wrote:
    If you want to do an outstanding job, you could take this opportunity to run a 3/4 line to the mechanical room, create a header loop with the 3/4 then branch each fixture off from there with an isolating valve and 1/2" to supply them (don't forget to label them!) - this would balance the system and not rob one fixtures water from another. One header loop for hot, one for cold.

    ~k~

    The longest run I have to make to the master bath is approx 50' to feed a whirlpool tub, shower stall, toilet, and vanity sink. This is also the farthest from the hot water heater. All the plumbing can be pretty much run in a straight line except an L off to feed the vanity sink.

    The guest/utility bath and kitchen are less than 15' from the inline feed, and hot water heater, on the opposite end of the house. I guess if I T-ed off the main feed lines and fed the master bath with 3/4, and the guest bath and kitchen with 1/2, that might even stuff out ehh??

    There are only 2 of us living here, and thats not going to change.......so having multiple useages going on at the same time is pretty rare

    Thanks forthe advice

    Steve
  4. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,384
    Location:
    Yakima WA
    One thing to realize is that 1/2" CPVC is considerable smaller inside than 1/2" copper and will carry much less water than copper. If you are committed to CPVC, then stay as large as possible for as long as possible.
  5. Kristi

    Kristi Tradesman Plumber

    Messages:
    176
    Location:
    Vancouver, BC
    If that's how you want to approach it, then that's totally fine... I personally would do the loop header instead of running a main line with branches to each fixture, especially with a big tub in the mix! It's more work and more pipe, but worth it in the end. It seems like your method would even out, teeing off 3/4 with 1/2, but all you have to do is read about everyones pressure woes to realize that that method is not ideal... go with Gary's idea (of staying large as possible) especially if you are going the tee off route. He's right about the cpvc, I personally only use it for irrigation and for pond-related stuff... only copper and/or ipex for me in the house, period. Good luck to you!
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,026
    Location:
    Cave Creek, Arizona
    header

    How is running a 3/4" line to the water heater, which might be the farthest point from the incoming water, and then running 1/2" lines all the way back more efficient and less restrictive flowwise, than taking the 1/2" branches off the 3/4" main as it passes them. Your way introduces a lot more piping and does not give ANY benefits, since valves can be installed anywhere they are desired.
  7. black hawk

    black hawk New Member

    Messages:
    4
    the in feed line comes into the house right alongside the water heater, NE corner of house. The guest bath, is directly across from it,the kitchen is adjacent to the west wall of the bath(sharing a wet wall)
    The master bath is on the north west/west wall, and is the farthest point from the water heater, main infeed. I dont know if that clarifies things,

    I'm on a pretty restrictive budget as far as the rebuild goes....hence saving some $$$ using cpvc. Our time is divided between actually rebuilding things, and doing salvage ( getting into demolition projects prior to the wrecking ball), and recycling materials to use ( construction site scavenging with permission). The 2 places we are making sure to use brandy new materials is plumbing, and electrical.

    I'm also a pretty rank amateur as far as all this goes, and am not understanding how a loop system that Krysti suggested works. Any suggestions on where to go look at a pic, or diagram??

    Thanks for the help so far guys, its appreciated!!
    Steve
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    IF I understand, then try this: If you have a single line with branches, when the first branch is calling for a bunch of hot water, there may not be much flow towards the second use point because things flow through the point of least resistance (the closer branch with fewer corners and distance). Now, if there is a loop, and things come off of the loop, the differential pressure would be less, and both would get similar flow. I could be all wet, but I think this is what is being discussed. They use a similar method in a fancy shower with multiple showerheads to make sure they all get similar pressure and volume capabilities.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,026
    Location:
    Cave Creek, Arizona
    loop

    Don't worry about it. Just do the system the way you planned to and it will work fine.
  10. black hawk

    black hawk New Member

    Messages:
    4
    So, let me get this straight in my head. In a loop system do you run your feed line to the farthest point in your system, dropping lines for individual fixtures, then run it back to the closest point.......again installing drops for fixtures, and then T the whole thing back in on itself near the infeed/hot water heater??

    Like I said, Im a rank amateur at this outside of minor repairs and outside nursery plumbing

    Thanks
    Steve
  11. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,734
    Location:
    Central Florida
    I have a center-fed (at the WH) 3/4" manifold for both hot and cold, running the 80' length of the house, with 1/2" fixture branches, each branch with its own cutoff valve. I wanted to do the loop thing, but wasn't sure how to do it, so I'm looking forward to a more elaborate description from Kristi :) .


    I used CPVC, partly because my under-slab copper developed leaks, and I was advised not to use copper because of my aggressive water. CPVC was clearly easiest for the DIYer to install, but requires some care. Other reasons - flow volumes, noise, and bacterial growth - favored both copper and CPVC depending on whose technical publications and studies you wanted to believe.

    I've recently learned more about PEX, and am impressed, but once again there are conflicting reports in all categories. It's clearly easy to install, but requires special (expensive) tooling. Fixture branch size recommended is typically 3/8", making me wonder if 1/2" CPVC is all that bad (compared with 1/2" copper). Probably not very noisy since it's normally not fastened securely to resonating structure. More prone to supporting bacterial growth according to one study (where CPVC was the winner), but the study was paid for by Flowguard.

    All in all, I'm happy with CPVC, and the 3/4" to 1/2" seems to work for me, but once again I'm looking forward to a more elaborate description of the "header loop"-style manifold from Kristi.
    -mike
  12. Kristi

    Kristi Tradesman Plumber

    Messages:
    176
    Location:
    Vancouver, BC
    HJ, I'm referring to balancing the system, as BlackHawk mentioned a bathroom far down the line that sounded like it would have high demand - and I've already agreed that he should go ahead with his original plan that it will be fine... I'm not sure if my suggestion warrants an entire dismissal, which makes it seem as if drops in pressure within a household aren't an issue out there. I'm saying that if it were my house, and i had the opportunity to start from scratch, here's what i personally would do. oh right, what is it that i would do? lol... ok, here goes, sorry i don't have any diagrams for you:

    I would most likely plan to have everything stemming from the same location, so i would bring the cold supply into the room where the water heater was going, and set up my header there - preferably in a central location in the house. I wouldn't branch off the cold to anything on my way there, except for the hot water tank.

    - 3/4 cold supply directly into the mechanical room (or closet, basement, etc...)
    - 3/4 hot supply from the heater
    - basically the loops look like butterfly wings, but squared off, and one for hot, one for cold
    - off one side of each "wing" are tees/ports for each fixture in the house
    - the loop is closed on itself
    - each loop is as big or as small as it needs to be, given the number of fixtures off of it. You can also add a couple extras and cap them off for future use.

    What's been created is a loop that circulates when water is called for - as the demand for water increases, it's called from the same header at the same point that the others are. This reduces issue of a drop in pressure from one fixture (say the guest toilet) robbing the supply from another fixture that may already be in use (say the ensuite shower, which is further down the line). When we have branches off of a main supply, we create the opportunity for the pressure to be unbalanced. If they are all coming from the same source (the header) then the demand is being distributed to them more equally. More pipe is used, because you run individual hot and cold lines to each fixture from the headers. It ends up looking like a maze of nice, straight, tidy electrical lines clipped up there - except it's pipe. It is not necessary to have shutoffs for each port unless you want to be able to isolate each fixture for whatever reason in the future, but i've used the same system for multi-suite homes and then I definitely install shutoffs so you can isolate them from eachother easily.

    I think that if "poppycock!" is hollered at this one, then I will just back way off and continue with my butterfly wings! I'm not forcing anyone else to do it, I just know that I have only had positive results from this practice when I've had the opportunity to implement it. As HJ said, go ahead with what you're doing, it's fine, it's how it's always been done, just run the 3/4 as far as you can.
  13. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,734
    Location:
    Central Florida
    I think that's what I was thinking of doing. Right now I have 2 T configurations (hot and cold), with the supply being the vertical line and the long manifold being the top (horizontal) line of the T. Each end of the manifold is capped. If I modify that by joining the capped ends of the manifold with another looong pipe do I arrive at your "looped header" layout? Only problem I see offhand, if that's correct, is that I've got 2 more 80' pipes -- hot water in one leaking BTUs, and cold water in the other sucking them up.
    Last edited: May 26, 2006
  14. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Messages:
    1,328
    Location:
    Columbus, OH
    I like it Kristi. I would do it in my house if I had the oppurtunity. Some dumb*** plumbed my house with 1/2 copper everywhere. 1in or .75 (hard to tell) galvanized from the street, then to 5/8 meter, then to 1/2 copper.

    Water comes in and splits to a hose bib, then splits for hotwater heater.
    If I recall correctly, both of those then split for laundry tub and washer then goes to the kitchen sink, then splits for the upstairs bath. When the washer is on, you're lucky to get enough pressure to get your hair wet in the shower. If the washer is on, pressing the sprayer button on the kitchen sink would cause NO water to come out of the faucet or the sprayer. Just no pressure left. Sucks.

    Jason
  15. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Pipe Loops

    Loops are always desired in municipal distributions systems and loop connections are made wherever possible.

    Loops in water distribution pipes ususlly maintain higher pressure at the delivery point, and they prevent stagnation that can occur at the end of a little used pipe, but they don't "circulate" because the pressure at both ends is the same.

    Loops in a residence operate the same way. If there is a demand such as a shower or toilet flush at some point off the loop, the water will flow from both ends of the loop to supply the flow. Since pressure drop is roughly proportional to the velocity squared, if half the flow goes through each pipe the pressure loss will be roughly 1/4 what it would be with a single pipe. It is the same effect as if a larger pipe with double the area is used for a single pipe.

    Loops don't need to be planned precisely. If you lay out the plumbing in an efficient manner without considering a loop, then you can look at the result and make a "cross connection" between the runs at some convenient point near the ends of the runs. Another obvious point is that you need to shut off both ends of the loop to isolate it.

    There is a serious disadvantage of using a loop or larger pipes for hot water distribution. If you are getting eqaul flow from both ends, thus at half the velocity, it will take twice as long and waste twice as much hot water, until the hot water arrives from the water heater.
  16. Kristi

    Kristi Tradesman Plumber

    Messages:
    176
    Location:
    Vancouver, BC
    Excellent info, thanks for clarifying and bringing it into the mix... :)

    ~k~
  17. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,734
    Location:
    Central Florida
    I solved the waiting-for-hot-water waste problem by installing a small recirculating pump between the hot and cold side of the fixtures at the far ends of the manifold. A pushbutton switch (AKA doorbell switch) fires up the pump, which stops automagically when it senses the water coming in the hot side is hot enough -- adjustable via a small control. Only downside, of course, is the coldwater side is also hot at that point. If I were building new, I'd plan on such an on-demand recirculator, and provide a separate return line to the WH.
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