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Context:

I'm putting in shallow (14" deep) water lines 500ft from my house to gardening areas where they will supply several hose bibs for take-off points for drip irrigation. I was thinking PEX, but the pressure drop would require at least 1" and that gets expensive, so now I'm considering regular black poly instead (PE4710) which I can get in 1" or 1-1/4" at a much cheaper price. I cannot backfill with sand, it'll have to be the soil I trenched out, which does have some rocks, so durability with rocks pressing against the pipe is a consideration.

Question:

What are the most reliable fittings (within a reasonable price range) for black poly to NPT adapters (to connect to galvanized tees and/or elbows for each metal riser) that are least likely to develop leaks or crack over time? PVC fittings sound brittle to me, insufficiently tight and maybe easy to crack by overclamping? I like the sound of metal barbed fittings. I want this to last for many years without needing repair. I've seen videos of folks sweating the pipe using metal barbed fittings with hose clamps, but I can't find any such metal fittings online that clearly state they are meant for black poly.

Or would anyone suggest I discard the poly idea and go with the more expensive 1" PEX? I do know what fittings I need for that.

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    I do not like galvanize fittings underground, they have a bad habit of rusting out. Mine were a lot deeper than 14 inches(4 or 5 feet). What is your frost level there if any?
    – crip659
    Apr 30, 2023 at 13:32
  • @crip659, thanks for the warning about galvanized, I didn't know that. Frost level here is nearly 40", no way can I bury that deep, so I'll be relying on winterization/draining at the low point.
    – Paul W
    Apr 30, 2023 at 17:18

2 Answers 2

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Polypropylene fittings work well, based on long experience, and are not brittle. You can get bronze if you really want to, or stainless steel these days.

If you are dedicated to metal risers, the internet (but for some reason not most local suppliers) has stainless steel threaded pipe and fittings (priced not too dear) due to the lead in galvanized pipe.

Schedule 80 PVC can also be threaded and won't become a rust bucket as galvanized does (yes, it does, the galvanizing has a very temporary impact on corrosion in service, as an observed fact) or you can use a suitable rot-resistant post and attach the black poly to it for another (and probably least-cost) rust-free option.

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  • Thanks for the warning about galvanized... didn't know that. I think PVC coming out of the ground looks ugly. But may black poly against a post might be acceptable. So polypropylene fittings are reliable enough to bury and stay good for years?
    – Paul W
    Apr 30, 2023 at 17:17
  • Decades. Multiple decades.
    – Ecnerwal
    Apr 30, 2023 at 18:25
  • For a lengthy, curvy route, would you recommend SIDR 11.5 black poly + PP insert fittings over PEX-B at the same diameter (1") & brass PEX fittings + copper crimp?
    – Paul W
    Apr 30, 2023 at 19:15
  • Yes. That's more commonly known as "160 PSI" and you likely don't need the pressure rating, but it goes with a thicker wall (than 100 PSI) that's more resistant to rocks.
    – Ecnerwal
    Apr 30, 2023 at 20:11
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Here in Fla. irrigation is everywhere. Poly fittings and polly risers are the #1 product to be used.

Since you have rocks PVC is the product to bury. Schedule 40 or even thinwall can work. All are available in 1" at a reasonable price. If yo go with the PVC all elbows and fittings are available and the polly risers will screw right into the NPT fittings.

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  • My trouble is that the ditch is not straight anywhere... curves the whole way.
    – Paul W
    Apr 30, 2023 at 17:17

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