[Eric K]

I use 43 x 3.5 Viton o-rings. They are difficult to install, but seal much better and last longer.

Here is what works best to install...

Put the o-rings in the groove dry. Then grease the inside of the pipe flange and the outside mating surface of the o-ring.

Push the pipe on as far as you can. Most likely it won't readily go on all the way.

Then hook up the springs and let the springs pull the pipe on. You may need to push some for final fit.