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Thread: PEX install on older home using too small diameter pipe?

  1. #1
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    Question PEX install on older home using too small diameter pipe?

    House built in 1958 and 1,200 sq. ft. and original galvanized was pretty slow-flowing. Paid plumber to redo house in PEX. He put 3/4 PEX from the water meter to the front of the house crawl space. There he transitioned it to 1/2 PEX (before it hits any branches) and from there *everything* else was done in 1/2 PEX, including all the hot water lines and all the hot/cold water branches to the toilets, sinks, etc. I'm not sure what size the cold from the water meter originally was but what's under the house (still there) is slightly over 1" OD so it's 3/4 galvanized and it measures the same in and out of the water heater. I was assuming he would put in the same thing as what was there because I asked him what he was putting in from the meter and he said 3/4" so I figured that was going to be the main line through the house. As it stands now the house essentially has 1/2" service since the 3/4" transitions to 1/2" before it ever hits anything?

    I'm just not sure if I am feelin' it how it was done. I'm worried there's too much trying to squeeze through a pipe that is slightly less than 1/2" in diameter. We do tend to use a lot of water here and have lots of things going at the same time.

    Also possibly pertinent to the story we have a 30,000 gallon in-ground pool in the backyard that here and there requires huge amounts of water.

    I was hoping to get the thoughts of the plumbers on the forum on what should be done (if anything).

    btw the type of PEX that was used was Uponor AquaPEX.

    Thanks for the help!

    2 toilets (1/2" PEX individual line to each one)
    2 bathroom sinks (1/2" PEX individual line to each one)
    1 shower/tub combo (1/2" PEX individual line)
    2 yard faucets (1/2" PEX individual line to each one)
    1 washing machine (1/2" PEX hot/cold)
    1 furnace humidifier (small copper line to it)
    1 40-gallon NG water heater (1/2" PEX in and out)
    1 kitchen sink, tied on to the sink are the takeoffs to the fridge and dishwasher (3/8" copper from 2005)

    Not sure if matters but my community uses IPC 2009.

    Water pipe sizing

    Last edited by Terry; 02-09-2014 at 05:59 PM.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    If he used a manifold and ran individual lines to each fixture, that may be sufficient, but the line to the house and to those manifolds needs to be larger for it to work. Many fixtures in the house are flow restricted, but a few of them can use all the volume they can get: tub, outside hose bibs, maybe the WM. ANd, the inlet and outlet to the WH would need to be bigger, on the outlet, until it met a manifold assuming he did home runs. If he did not do home runs, then you generally want larger pipe to the area, then branch off that with smaller pipe for the individual fixtures.
    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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    Thanks for the reply!

    oops! Forgot to say he used 1 main cold line with everything branching off off that (with the hot water heater coming last) and then one main hot line with everything branching off of that. I guess that is a trunk and branch system?

    I originally thought he was using the manifold system and I brought that up when he was starting and he said something about that was only for natural gas? I dropped it since I didn't know what he meant and I'm no expert on PEX. In my Google searches since the install it seems like manifolds are especially useful for larger homes. I'm fine not using manifolds as long as we have large enough pipe to give all the water that is needed...

    You're thinking what I am thinking: larger pipe to the area with smaller pipe branching off....

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    Moderator & Master Plumber hj's Avatar
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    a 3/4" PEX main line is not much larger than a 1/2" copper or steel pipe. so he did not do you any favors by using it. And, since 1/2" PEX is MUCH smaller than copper or steel, it is inadequate for anything other than the final runs to each fixture/faucet. I would either have NOT used PEX, or would have used one size larger for each application.
    Licensed residential and commercial plumber

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    Forum Admin, Expert Plumber Terry's Avatar
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    I would have brought in a 1" line from the street.
    The most I will use 1/2" for is two plumbing fixtures.
    3/4" should have been run to the water heater.
    I would pull a permit and have it inspected. Then it's not your word, but the inspectors.
    In third world countries, they don't have that option.
    Here in the US, we have agencies and inspections to protect consumers.

    Water pipe sizing



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    Terry and hj: Thanks for your replies!


    I just got out from the crawlspace and took my micrometer to make sure of the sizes and after looking at the piping charts I'll have to change some of what I previously said. Original 3/4" galvanized in from the meter and changes at the front of the house to 1/2" galvanized with the ONLY branch off the 3/4" going to the front yard faucet. EVERYTHING else was 1/2" galvanized. including in/out of the water heater. What the plumber did was EXACTLY mirror what was there, including the front yard faucet being the only branch on the 3/4" PEX pipe.

    We paid $2,100 for the whole deal (re-pipe house and dig up 40' of front yard to replace pipe to the meter) and was planning on this being an upgrade but guess it was a downgrade seeing as the 1/2" PEX installed is much smaller than the 1/2" galvanized that was original to the house.

    I just wish he had mentioned some stuff to me about sizes and different choices. He never said a thing. I was here watching the whole thing but he moves so fast that it didn't 'click' on me as to what was going on. It wasn't till later that day that I got under the home and looked at what was done and thought about it for a bit.

    I would pull a permit and have it inspected. Then it's not your word, but the inspectors.
    I'm not sure of permits and stuff. I know when we had the sewer line replaced (it had totally degraded) a city inspector came out and looked at it all. I was here the entire water re-piping and no inspector ever came out that I saw. Not sure what the plumber did regarding all of that. A side note is one of our family friends is one of the city inspectors where I live and I could call him up and get all the info I need but have decided to hold off until the plumber comes out and see what he says. He's coming out tomorrow. I'd like him to just extend the 3/4" to the water heater and just branch off of that. I looked under there and there's plenty of slack to hook the branches onto the new 3/4" I can't believe it would take him very long. I'm just not sure if that's being reasonable (seeing that he just mirrored what was there) or if I should just live with it.

    I would have brought in a 1" line from the street.
    I had a sheet of paper with questions when he came for the estimate and I asked him "3/4 or 1 inch" for the pipe from the meter and he said 3/4. When he said that I took it that 1" wouldn't work?

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    Forum Admin, Expert Plumber Terry's Avatar
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    Who in Hell mirrors 1958 plumbing?
    Codes have changed dramaticly since the 50's
    Heck, they were just getting used to the idea that people might want more than one bath.

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    Quote Originally Posted by Terry View Post
    Who in Hell mirrors 1958 plumbing?
    Codes have changed dramaticly since the 50's
    Heck, they were just getting used to the idea that people might want more than one bath.

    Yup. He did say code required a shutoff valve in the front so one was added there. That was about the only change that he made as far as I can see.

    uggg....this whole thing makes me feel like Lloyd Bridges "Looks like I picked the wrong week to quit drinking!"

    I just hope when he comes tomorrow I can say the right things to get him to make those changes and not charge me. I'm not trying to make him mad--just fix it.
    Last edited by pexhouse; 02-05-2014 at 04:32 PM.

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    When you consider that the 1/2" piping was originally 0.622" i.d. and your NEW PEX is 0.645 O.D., he didn't really "replicate" the original installation, and it is probably not much better than the plugged up one he eliminated. Incidentally, only hacks and low bidders ever piped houses with 1/2" pipes, whether copper or galvanized, and they still do.
    Last edited by hj; 02-06-2014 at 05:59 AM.
    Licensed residential and commercial plumber

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    agreed. He'll be here in an hour and will report back how it goes.

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    ok he was just here and left. He said he put it all in according to code. The code for here says 3/4" from the meter to the house and 1/2" from that and that's what the code says. He said it would go to 3/4 in the house if the house had 2-1/2 baths or more (I believe that was the number). I showed him how the size of the 1/2" PEX is MUCH smaller than the original 1/2" galvanized that was there. He didn't know that and went and got 1/2" PEX, copper and galvanized off his truck and sure enough it is much smaller. He said he'd do 3/4" if I wanted it but that would be extra $$$$. He said going to 3/4" wouldn't help the pressure or flow at all.


    sigh....guess we're stuck at the small size for good.

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    The fire department may offer to fill your pool for a fee. http://www.dailystatesman.com/story/1983575.html

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    ok I looked over the code for my community (IPC 2009) and took me awhile to find this but I think the bottom graph would apply to me?


    http://publicecodes.cyberregs.com/ic...ppe_sec004.htm


    Smallest "Meter and service pipe" is 3/4", while the smallest "distribution pipe" is 1/2". However, there's a footnote for the 1/2", "a.", and it says "a. Minimum size for building supply is 3/4-inch pipe." If I understand it correctly, it's meaning the trunk supply of the building and the smallest is 3/4" ? I'm just wanting to make sure I do my homework and have hard facts before I start making some phone calls....and make myself look like an idiot (BTDT).

    Also looking at terry's pipe sizing chart here http://www.terrylove.com/watersize.htm points to 3/4" but I want something hard written in the plumbing code to have my back.


    Thanks all !

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    Forum Admin, Expert Plumber Terry's Avatar
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    5. To determine the size of each water distribution pipe, start at the most remote outlet on each branch (either hot or cold branch) and, working back toward the main distribution pipe to the building, add up the water supply fixture unit demand passing through each segment of the distribution system using the related hot or cold column of Table E103.3(2). Knowing demand, the size of each segment shall be read from the second left-hand column of the same table and maximum developed length column selected in Steps 1 and 2, under the same or next smaller size meter row. In no case does the size of any branch or main need to be larger that the size of the main distribution pipe to the building established in Step 4.

    Your plumber (I would love to see his license) doesn't understand that you count the fixture units backwards. That means the pipe increases in size in the direction of the water meter.
    The "most" you should run on 1/2" is two plumbing fixtures. Something like a lav and a tub. Some will do the complete bathroom set.
    But then you have a washer, kitchen sink, dishwasher, two outside hosebibs, and the second bathroom.
    This means he needed to keep the 3/4" and have 1/2" branches off of that. He needs to work backwards. Though I have to admit, he may be a little backwards already.
    If you had pulled a permit, the "inspector" would be telling him all of this. It shouldn't be your job to inform him.

    You should be able to look up your plumbers license status on your state's website.

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    Terry: thanks for your reply!

    I've never done anything to do with permits or stuff like that before. However, as I said before I know one of the inspectors for my city and will call him here today or tomorrow.

    One thing I just noticed upon closer examination of your piping size chart:

    adding my fixture units:

    bath/shower: 4.0
    clothes washer: 4.0
    Dishwasher: 1.5
    Hose bib: 2.5
    add hose bib: 1.0
    kitchen sink: 1.5
    lavatory: 1.0
    lavatory: 1.0
    toilet 1.6: 2.5
    toilet 1.6: 2.5

    ---------------------

    total: 21.5

    looks like 1" from meter through trunk of the house?

    He'll have a coronary if he has to dig up the yard at his cost. Might get interesting.

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