Cementing PVC

[cabinetman]

I'm using schedule 40 PVC (white) for some irrigation changes. Is it necessary to use the primer, or is just using the cement sufficient? In the past making repairs, I've scuffed lightly the mating parts with 400x wet-or-dry sandpaper and just used the cement without problems. If the primer is necessary, how long does it have to dry, or does it have to dry?
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[jking]

I would use the primer. To me, using the primer would seem to be much quicker than sandpaper. I don't recall there being much wait time. I always prime both parts of the connection and then apply the cement right after. Don't forget to hold the connection together for about 30 seconds. The cement will tend to push the connection apart until it starts to set.

[gjat]

If the joint is after the timer contolled selenoid valve, then cement alone is suitable. Cleaned and scuffed gives a great joint. If it's before the valve (between meter and selenoid valves), you will want to use primer. There are different type primers. Most primers take just a few minutes to dry, read the label.

[Uncle Cracker]

Primer removes the gloss from the pipe, which you can do with sandpaper, but what primer also does is soften the pipe to make the solvent cement penetrate and work better. Sandpaper does not do this. Using a "hot" glue makes the surface prep less important, however, so if you've got one of the hotter cements (they're usually blue in color) then you've got no worries.

More important is to not use cement that is old or contaminated (it gets watery or jelly-like), and to thoroughly coat both the pipe and the fitting, while not allowing excess cement to run down inside or outside the pipe (it will weaken the pipe, and possibly cause a blowout sometime in the future). Turn the joint a quarter turn as you are assembling it, to evenly distribute the cement.

[Black wallnut]

I scuff with sand paper as well as use both primer and cement. I've yet to have a joint fail or leak in sizes from 3/4" to 4".

[master53yoda]

one of the things that I have found that makes a big difference is to use a deburing tool on the outside of the pipe if it was cut off with one of the cutting knives rather then a saw.

with the burr on there it scraps all the glue off the female fitting as it is inserted.this can leave the joint with air gaps .

I have never sanded PVC but have always used the primer. the sanding would remove the burr. the primer i use is normally the blue primer and it dries in seconds.

[BigguyZ]

I've only sanded if the pipe was painted over or especially dirty. Even then I use primer. As far as I know, plumbing codes require the use of primer for all glue joints. I'm not big on codes, as a lot of them are BS. But, if you can easily/ cheaply meet code- why not?

ABS can use just the glue, but from what I've been told PVC needs the primer for a proper joint.

I also second the note about having fresh cement. I've sadly enough tried to use cement past its prime, and it have never led to good things....

[Rand]

Yes. Use the primer.

You don't have to wait for it to dry. Just prime all mating surfaces and put cement on them. I prefer to use the hot cement too. It dries much faster. Who want to wait 8 hours to pressurize something???

[cabinetman]

A plumber once told me that if the cement cans are stored upside down (on their cap), it will increase their shelf life. Is there any truth to that?
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[Uncle Cracker]

A plumber once told me that if the cement cans are stored upside down (on their cap), it will increase their shelf life. Is their any truth to that?
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Not to my knowledge... Spent 20 years in a sprinkler supply house, and never saw a can upside down, and the manufacturers don't ship them that way. If there's an air leak, the contents will spoil either way, and also might leak out if upside down.

[chopnhack]

Use the primer, my uncle is a plumber and taught me a tip about it, have a clean rag, apply the primer with the dauber then wipe it right off, no wait time and no puddling