PEX tubing conversion

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by weekendmechanic, Jun 3, 2014.

  1. weekendmechanic

    weekendmechanic New Member

    Messages:
    6
    Location:
    New York
    Hello everyone,

    I currently have 1/2 inch copper pipe run throughout my house but after 60-something years of use it's beginning to show it's age (pinholes and whatnot).

    I have decided to switch to PEX and had a few questions about it:

    I have a 3/4 line coming into my basement which then feeds to a water meter at 5/8. (This is stamped on the meter as well as the pipe is smaller than the service line) So I have a 5/8 pipe to start with.

    First question: If I connect that 5/8 copper line after the meter to a 3/4 PEX line to use as a trunk what will this do to my flow (gpm) as well as my pressure?

    Second question: My original understanding was to connect the 5/8 pipe after my water meter with a sharkbite connector to a copper manifold with ball valves on it and use a 3/4 inch line from the manifold as a trunk before Teeing off to 1/2 for each fixture. Does this seem like a good method for running my pipes?

    Third question: I have steam heat so I use cast iron piping from the boiler to the radiators and I am not going to replace them. There is a 1/2 inch supply water line feeding into my boiler. Do I need to use pex with an oxygen barrier or is regular pex piping fine for this application?

    Fourth question: How far should I place the PEX piping from the flue from the boiler and water heater? My understanding is that too close can cause the pipes to melt.

    Last question: Are some PEX brands better than others?

    Thanks for reading, this is going to be an interesting project.
    Last edited by a moderator: Jun 3, 2014
  2. JustAHomeOwner

    JustAHomeOwner Member

    Messages:
    41
    Location:
    NY
    Last edited by a moderator: Jun 3, 2014
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    A short length pipe diameter restriction (like in your meter) acts more like a venturi...the fluid speeds up going through it, and then returns to 'normal' velocity, with only a very small reduction in flow capacity. You might want to use 1" pex to your manifolds.
  4. weekendmechanic

    weekendmechanic New Member

    Messages:
    6
    Location:
    New York
    JustAHomeOwner: Sounds like I'll stick to 3/4 until the last minute. I also read those documents as well as your previous posts about pex and their fittings and that opened a can of worms with me.

    I'm very suspicious of compression fittings, even more since cash-acme compression fittings aren't explicitly compatible with other brands. Since Uponor seems to be the best brand out there and they don't really have their own compression fittings I think I'll get their copper fittings to solder on the pipe and crimp the pex to the adapter-part of that fitting. Seems like a stronger connection anyway.

    Jadnashua: the venturi effect makes perfect sense with the only side effect of a slight loss of volume since we're not talking about a long pipe run. I think 1" pipe would make sense but after the run from the 3/4 pipe coming in the house as well as the water main, do you really think the 1 inch pipe with a 0.862 inner diameter would make a noticeable difference?
  5. Reach4

    Reach4 Well-Known Member

    Messages:
    2,432
    Location:
    IL
    Couple of random comments not that relevant to most of your post:

    1/2 inch PEX is smaller than 1/2 inch copper... same with 3/4.

    Don't make the hot water line to the bathroom sink bigger than needed because bigger pipe slows getting hot water. If you want to consider putting in a hot water recirculation system for instant hot, this is the time to think about that.
  6. JustAHomeOwner

    JustAHomeOwner Member

    Messages:
    41
    Location:
    NY
    I hesitate to say this here since I have zero experience with other connection types but here's my take on Upnor. I bought a 12v Milwaukee expander, 2 batteries, I already had a 12v charger for those, and 2 Milwaukee expanding heads, 3/4" and 5/8". So far I've used the 3/4" for re-routing maybe 60' or so of piping for 180 degree hydronics that was in service most of this past winter with no problems. Currently I'm in the process of running 3/4" Upnor pex for a bathroom I'm framing in. Coming from someone who's quite used to running copper: those Pex tools were a bit pricey as are the brass fittings and the pex itself. The trade off is in the ease and speed of installation with EASE in bold letters. Making a connection with that system takes maybe 15 seconds and as far as I can tell, discounting of course what a fool might do, it's fool proof. Instead of being a hard working homeowner, if I were something I'm not, a plumber or a contractor and had to compete with pricing quotes I can well imagine making quotes for and using less expensive systems.

    Best on your project and be well.
  7. Kiton

    Kiton Member

    Messages:
    61
    Location:
    Quebec
    I am not a plumber, but I do have a lot of chemical pipe work and welding experience, so I can only offer a few tips along the way. I have just re piped all my hot water lines and will do the cold in the coming few weeks.

    After trying both Bow and Uponor, like others, I think Uponor is the way to go.
    I may get called out on this, but I agree with you, I would never rely on a sharbite for the long term. If you don't finish the project and you need to use a sharkbite until you can come back and wrap the job, fine. The kitchen installers put a few in my kitchen (which I have since pulled) and they worked fine in the short term.
    In my case it was 1/2 NPT out of the meter, to 3/4 pex to a manifold then 1/2 to fixtures. Except for the hotwater heater, which got 3/4 pex. I did the math for water consumption, and running a line to each fixture (the Home Run systems) used way too much hot water over the life of the home for my taste.

    Attached Files:

  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    One thing to keep in mind when using anyone's pex connectors...each connection adds a little friction to the flow and, they are smaller than the ID of the pipe. Uphonor's expansion fittings have a larger ID than those designed to crimp on, but are still smaller than the pipe's id. You may never notice the difference between 3/4" pex and 1" pex to the manifolds, but it would depend on what you were feeding...have everything running at the same time, and it would be noticeable. How often or if that would ever happen depends on the situation and the user(s).
  9. Kiton

    Kiton Member

    Messages:
    61
    Location:
    Quebec
    Very good point, we are two people at home and a single bathroom on the main level.
    The odds of a toilet flush while someone showers etc etc is about zero.
  10. weekendmechanic

    weekendmechanic New Member

    Messages:
    6
    Location:
    New York
    Reach4: My meter is 5/8 so in staying relevant to pex having smaller inner diameters I have decided to run 3/4 pex to mainly everything since the inner diameter is slightly larger than 5/8 copper and offers each fixture the most amount of water volume until the last second when the fixture downsizes the pipe.

    As for running the 1/2 pex for hot water only to each fixture that makes perfect sense. If every fixture has the same static pressure it only stands to reason that a smaller volume pipe would flush out all of the cold water faster than larger diameter pipe since there is less water flowing at the same psi. (thus wasting less water).


    Justahomeowner: I cringed when I saw some of the prices on those expanders. It looks like all pex-a pipes use expansion fittings but I just can't justify spending that much. I saw Rifeng is pex-b and has a respectable reputation. The difference is I can use the clamp fittings with peace of mind. Yes some people use pex-a with clamp fittings but the way I see it, a job is only worth doing if it is done correctly.

    I'm typically a "measure twice cut once" worker but what really made me switch to pex-B is that when I connect my pex to existing copper pipe, for the shower manifold or hot water heater, this brand (rifeng) makes adapters for (3/4 pex to 1/2 copper) (as well as 1/2 to 1/2) that you sweat right onto the pipe itself. - not to mention each adapter is $1-2 at most as opposed to some of the $7-$9 Uponors.

    If I can use the same brand of fittings as the pipe it makes me feel much better since there is a less of a chance of it failing for incompatiblity reasons.

    Pex-a seems to be what a true professional would use and makes sense for someone who has to use it on a daily basis. What sparked my whole idea for the switch was the need to install a sprinkler system but there being poor gpm at the hose bib (which I also learned is the wrong way to connect it).

    Kiton: I would only see the larger home runs using more water for one of two reasons, either you are using a fixture that connects directly to the 3/4 run without a reduction from the fixture itself, (those awesome wanton rain-showerheads) or if you are purging all of the cold water from a 3/4 line before the water actually heats up.

    I decided to compromise my system between homeruns and branches. I will be running 3/4 to each room that has fixtures. From there branching off at 3/4 directly to each fixture and then using a (3/4 pex to 1/2 copper fitting). All of my faucets use 1/2. My toilet I believe has a 3/8 fitting but I will have to look into that tomorrow.



    Tomorrow I will look into the mounting equipment since I understand pex moves back and forth from expansion. Over time this can damage the pipe from abrasion unless it is properly suspended and has the occasional extra loop for movement.
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    Three advantages of pex-a: smaller turn radius, larger ID of fittings, and the ability to recover from a kink (-b, and -c require you to cut out that section and replace with a fitting if you kink things, and you may not have enough remaining length, making it harder).

    The manual expander tools are cheaper, but are tough on your hand and arm. Some people end up buying one and then selling it on the auction site, sometimes, buying a used one and getting about the same price when they sell.
  12. weekendmechanic

    weekendmechanic New Member

    Messages:
    6
    Location:
    New York
    Granted. I'm no stranger to e-to-the-bay and those are some good benefits, namely the inner diameter. If you do kink a pex-b though what are the potential consequences for not splicing the pipe?

    Also how do I determine the minimum turn radius for a pex-b? Trial and error perhaps? I remember reading something about "6 times the pipe's diameter"
  13. Kiton

    Kiton Member

    Messages:
    61
    Location:
    Quebec
    I believe (but you should double check) the basic rule of thumb is 1 inch per hundred feet per 10 degrees of temperature change.
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    With pex-a, to restore the tubing to its nominal diameter and shape, you'd use a heat gun - the cross-linking of the polymer chains is strong enough to retain full strength of the tubing. Try that on pex-b or pex-c, and you may never restore it to full diameter or shape, and you may have a restriction with associated turbulence and flow issues. It might no longer be as strong. Now, this is theoretical, in practice all I know is that they tell you not to do it!

    Each brand and size of pex will have listed in its specs the minimum bend radius, so general rules are not too useful. If you're trying a fairly tight bend, sometimes the best way to achieve that is with the extra cost bend supports that lock around the tubing and prevent it from kinking, or pulling on subsequent sections while trying to straighten itself back out again.
  15. weekendmechanic

    weekendmechanic New Member

    Messages:
    6
    Location:
    New York
    I definitely see myself ordering some bend supports and holders to keep it against the ceiling joists of my basement. I just ran into a situation though.

    I want to connect a 1" pex pipe from the 5/8 water main (male) until it gets to the manifold and then branch off from there to 3/4. (all for the purpose of the sprinkler getting the best flow). Only problem is I can't find an adapter to do this.

    Here is a picture, maybe you can make a suggestion for how to connect the pex to the brass fitting on the water main? Right above the male connectors on the main, there is a 5/8 stamped

    https://www.dropbox.com/s/7o7hpl69j41y6ge/20140605_224946.jpg

    Thanks guys,
  16. weekendmechanic

    weekendmechanic New Member

    Messages:
    6
    Location:
    New York
    So I went to my water district today and found out that the 5/8 stamped on the meter only refers to the outside nut size used to connect the meter to the supply line. That meter is really a 1/2 inch meter (because of the tail fittings) but supports a 25gpm flow rate. (who knew..)

    I was advised that the gate valve before the meter which is seized on the line is really limiting flow because of the design of the valve.

    Thoughts?
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    Can't help on the restriction of the valve, but one thing to consider on your tubing...the max velocity through water pipe to minimize turbulence or cavitation is about 5-6fps...so, you can figure out how many gpm you can get with various pipe sizes safely. Since the area goes up by the square of the radius...a little increase in size, significantly increases the available volume, as well as reduces the friction in the pipe. Static pressure will be the same whether the pipe is the size of a soda straw, or a fire hose, but the volume and dynamic pressure will drop with smaller pipes as the friction increases.

    Gate valves can be problematic...when they get old, the gate tends to break off from the shaft when you try to use it. Give me a nice ball valve any day!
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