Pex in conduit - will I be able to pull this?

babaganooshApril 1, 2012

Am I in for trouble? I never worked with PEX before and someone locally thought this wasn't going to work:

I have a 200' run of 2" grey eletrical conduit buried between my house and a shed. I want to be able to have a faucet for a garden hose out there so I don't have to drag a long hose from the house when I need to water in that part of the yard.

I think I remember about electrical code years ago - a conduit run could only have a maximum number of degrees from all the turns before an access panel was needed. I forget that number but thought it was interesting as a way to keep you from making things hard on yourself.

So, with this 200' run, I want to get PEX in there to get the water out to the shed.

There's a total of 4 90 degree turns in the run (being conduit, the curves ARE wide (vs. DWV sched 40 / 80 connectors that are sharper turns).

1 90 is at the shed - there's a vertical pipe into the ground, and it hits the 90 at the bottom. straight run for most of the distance. a 90 tuns towars the house and then a right and left 90 to get around existing things and into the house.

I have pull lines in there now. being that I haven't worked with pex, is it flexible enough to get around these 4 90 deg. turns? I'd like 3/4" PEX, but as a fallback, could I use 1/2" and still get any kind of pressure / flow out of it after 200'?

1 last question - I was thinking of pulling from the house - keep the pex out of sunlight. but that means the entire length of pipe has to make the 3 90s right near the house (but I can push the tubing around those turns as someone pulls also?. vs. if I start at the shed, then only the last 20' of pex has to wind its way past the 3 90s. but then pushing won't really work well. I'll have to pull only.

so in summary, can I run 200' of 3/4" pex through 2" conduit with 4 90 deg. turns?


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The NEC limits the degrees of turns between pull points to 360. The concern is that there be no damage to the insulation on the conductors. And I once tried to do a pull with 450 degrees of turns. No doubt about it, 360 is the practical limit. Never tried to pull PEX in a conduit. I suspect that the radius of the conduit elbows and the stiffness of the PEX will make it impossible. If you try it, use pulling compound generously on the PEX as it enters the conduit. How pulling compound affects the PEX, if it does, I do not know. If you hear an electrician say to use vaseline, do not take that seriously. It is slang for pulling compound.

    Bookmark   April 1, 2012 at 8:56PM
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stiffness of the PEX will make it impossible!?!?

is there a way to soften the pex to pull it? are there more flexible versions of PEX? are thre alternatives to pex?
going to 1/2" pex would increase the odds of success I would hope. but would you get any usable flow / pressure after 200'?!

    Bookmark   April 1, 2012 at 9:03PM
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The use of pulling compound on PEX most likely will not damage the pipe. Pulling compound does not damage any of the non-metallic materials used in electrical wiring and it is safe to use with bare hands.
Your answers will come from experimenting.

    Bookmark   April 2, 2012 at 8:08AM
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I think this won't work. Typically, with standard PEX tubing, you can expect it to have a bend radius of 6 times its diameter and still avoid kinking. With 3/4", that would be 4.5" radius. I doubt your existing radii are that broad and, even if they were, I doubt you could pull through four of them.

Not in the bus. Just looked it up.

    Bookmark   April 2, 2012 at 9:46AM
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"I doubt your existing radii are that broad "

2 inch PVC electrical conduit should be larger than 4.5 inch band radius.

You will likely need a steel fish tape and plenty of puling lube.

Some compressed air and a foam 'bunny' can be used to pull in some puling twine, then use that to pull in a fish tape, than pull in the PEX.

Long pulls with 360 degree of bends are not cor the squeamish.

    Bookmark   April 2, 2012 at 10:20AM
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Well, I said, I'm not the pro here. Certainly don't have the experience of several others. I'm just nervous about that PEX becoming a constantly pressurized water-line after the potential abuse during the pull. May be needlessly doubtful.

    Bookmark   April 2, 2012 at 12:55PM
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This isn't encouraging! Yes, there's a couple pull strings in the pipe already. I'm trying to figure how to have a 3rd? string in there that doesn't interfere with the pull but will be available if the pull strings / pex seperate.

pulling lube!? Had figured I didn't want the PEX exposed to it. Have to check with manufacturer to see if they have any issues with that.

So is there something more flexible than PEX that can stand up to pressure / time underground in a pipe?

would trying to warm the pex make any sense to make it more flexible?

PEX doesn't like sunlight, right? That's over months, right? An afternoon in the shade as we try to pull it from outside the house is / is not a big deal? More the abuse we will put it through to get it in the pipe will be worse : ) ?

I was thinking of pulling from the basement to keep it out of sunlight. But 3 of the curves are within 15 feet of the house so rather than have to pull 185' of pex through those turns, we'll save those curves for just the front 15' of the pex? And yeah, worst case we could get to at least 2 of the curves - the ground is open at these curves (the pipe originally ended outside the house and I ran it into the basement just recently by adding 2 90s (and taking out 1 90).

the pull string is

pulling on them for 200' - on the curves - could it cut through the cuves?!

the pull strings are

    Bookmark   April 2, 2012 at 12:58PM
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Sunlight on the PEX for few hours isn't a problem but I think you're right in worrying about the rest.

Another way to think about the curves......maybe consider doing the closest curves first. It will either go or it won't go and you'll have your answer sooner rather than later.

I'm over my head.....sorry.

    Bookmark   April 2, 2012 at 1:31PM
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What are the pull strings for?

You cannot install power lines in the conduit once the water line is in.

    Bookmark   April 2, 2012 at 2:38PM
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pull strings?! For pulling the PEX! I heard someone mention pushing the pex, but that's got to be like pushing a wet noodle?

    Bookmark   April 2, 2012 at 3:40PM
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I first thought this was a April Fool's joke...

    Bookmark   April 2, 2012 at 4:24PM
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"pull strings?! For pulling the PEX!"

You are very likely to need more than string.

Rope or metal fish tape.

    Bookmark   April 2, 2012 at 4:39PM
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AWWWW! that's not nice! : )

I was bumming at how this was sounding futile. But I'm realizing now - 2 of the 90s are buried. 2 more are right outside the house and open / accessible since I just put them in. I'll just cut the pipe, seperating the 2 exposed 90s from the 2 buried 90s. then I can pull in 2 stages.

    Bookmark   April 2, 2012 at 4:43PM
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For pulling, I would use a rope that is larger/stronger than you imagine you will need. Rope will be less likely to damage the conduit inside. A steel cable could cut the conduit on the inside of the bends. The heaviest pull in which I was personally involved was about 260 feet of 4 conductors of 350kcm copper plus a smaller conductor for the neutral in 3 1/2" aluminum conduit. We used a wrecker truck with the steel cable removed from the winch to pull the rope and applied pulling compound generously to the conductors as they entered the conduit. Still was not easy.

    Bookmark   April 2, 2012 at 7:48PM
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"I would use a rope that is larger/stronger than you imagine you will need."

The problem with rope is that it stretches under load.

Use a steel fish tape.
They are designed for this.

    Bookmark   April 3, 2012 at 10:46AM
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Out of curiosity I pulled up my PVC electrical conduit catalogs and checked the radius of the bends for 90 deg sweep elbows and found they are available it 9.75", 12", 18" & 24" radius.

I then pulled up the PPFA (Plastic Pipe & Fitting Assoc.) PEX installation handbook & the Zurn Pipe Co-PEX Installation guide book.

Both publications say the minimum allowable bend in PEX tubing is 6x the OD when the tubing is being bent in the same direction as the natural curl of the tubing from the roll. If you have to bend the PEX contrary to the natural curve you must multiply that by 3.

1/2" Pex has an OD of 0.625" so 6 times that would be 3.75" (most installation manuals state a minimum of 4" for 1/2" PEX) That is assuming the bend is with the natural curl of the PEX, if the bend is opposite the natural curl the minimum would then be a 12" radius.

Theoretically you could pull the PEX, but before you do, ask yourself a couple questions:

How deep is the conduit? Generally they are not too deep because they don't have to worry about electric freezing, but a water line has to be 6" below your frost depth. Are you sure the conduit is deep enough all the way?

Now ask yourself if you can live with the pressure loss?
A hose bibb is rated at 5gpm and at 5gpm the Friction head loss in 1/2" PEX is 31.4psi per your loss in the PEX run alone would be 62.8psi, never mind how much loss a garden hose would add on the load end.

    Bookmark   April 3, 2012 at 11:35AM
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Sophie Wheeler

Just rent a trencher and run polyethylene or PVC like normal. It will be a LOT less trouble and money. PEX isn't cheap, and trying to pull it through conduit will give you a lot of gray hairs if it can be done at all. Poly or PVC will be a LOT of cheaper, and it only cost me $100 to rent a decent Honda trencher for 4 hours. Some equipment rental locations will allow you to pay for the 4 hour rental late on a Saturday and just return it on Monday morning if they are closed on Sunday. That way you can add more than just one new outlet. Don't forget the backflow preventers!

    Bookmark   April 3, 2012 at 3:18PM
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I'm with Holly. I'd go with Poly.

    Bookmark   April 3, 2012 at 4:38PM
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