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I am building an irrigation system. The instructions that came with the Orbit manifold say use PVC cement. Watching videos like below I see this PVC glued with or without primer.

With primer
Without primer

Here is the PVC pipe that I have.

So what glue do I use and do I need primer or not?

Grrr here is a study showing that priming does not help at all, on the contrary.

So what are they selling us in the stores? This looks like a scientific study to me, tests, data etc., so it is not story based but real hard fact-based.

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    More important than primer is to lightly sand the surface to be glued. Uv causes some damage to the polymer ,depending on exposure. Testing was done on epoxy FRP but any polymer is affected by UV. I have sanded all connections in my 60 sprinkler system and never seen a bad joint. May 10, 2022 at 21:10
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    The experimental design is garbage. By only inserting 1/4" it's not evaluating a proper joint.
    – Ecnerwal
    May 10, 2022 at 21:43
  • Even at today's ridiculous prices (I just checked a big-box, it's $3 and change for the smallest bottle), it seems silly to skimp by skipping the primer in comparison to the cost of having to dig it up and fix leaking joints.
    – FreeMan
    May 11, 2022 at 12:06

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You can do what you want but I'd never glue a joint without primer. Pick a glue and follow the directions. One flaw in the tests were that the pipes were not installed to the depth of the fittings, a space was left to see if the joint would fail under compression. Much of the joint's strength is from the pipes being inserted while twisting until the pipe "bottoms out". Another main flaw is that the joints were not tested by pressurizing them with water and if you're building an irrigation system, you don't want any leaks. I have made countless PVC joints for spas, hot tubs and sprinkler system and have never had one fail.

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  • Ok I will go with that do some more research when I get back home. The first guy in the store told me to use System 636 but his colleague told me he was wrong and told me primer + glue so I took your advice both for now
    – MiniMe
    May 10, 2022 at 21:45
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We always use primer on the “high pressure side” of the valves, but not the sprinkler side. We never sand anything, but always use joints that have a good overlap. The plumber I work with has over 30 years experience, and I have been assisting for four years.

Where the plumbing code here requires primer on PVC, we use the primer with dye and make sure it is visible outside the finished joint.

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