Correct way to install PVC union

[Newms118]

I have a standard PVC union from Lowes, and was wondering if it matters if the union is installed with the O-ring on the top or bottom (this is for vertical installation). I read that you want to keep the O-ring on the bottom so that its held in place by gravity, but if i do this, ill have to glue the PVC in my stand (rather than the garage) and better chance for a mess.

What do you guys think?

[TeHGuy]

the union being sealed will hold the oring in place. Do what works best for you.

[Da Maui life]

Did all mine with the o-ring on the bottom, that way they don’t fall out or get misaligned and pinched. But you can do what works best for your application, try putting. A very thin coat of plumbers grease on the o-ring before assembling may help hold in place top install, if they tend to fall out.

I keep o-rings on hand like this kit.
http://www.amazon.com/Neiko-407-Piece-Rubber-O-Ring-Assortment/dp/B000OMKIDI/ref=sr_1_1?ie=UTF8&qid=1381986079&sr=8-1&keywords=o-ring+kits

[necessary_evil]

The O ring on the bottom is the best way by far for the above listed reasons. Also using a aqua safe silicone lube isn't a bad idea if you're frequently using the using the union

[Newms118]

Thanks guys, will put o ring on bottom

[Tom39]

IMO, the position of the o-ring makes no difference as long as it is properly in it's place. As for the orientation of the union, I always make sure that the nut is at the top so that when it is taken apart it doesn't fall down the pipe. Plus not having to lift the nut into place while lining up the fitting and making sure the o-ring is in place makes things a bit easier.

HIH
Tom G