TopFeatured.com

Hello Everyone
I have a question about making a watertight piston head. I am trying to use a similar design as seen in this video to allow for a watertight piston head, but im not sure how much space I am supposed to give. I have a 4-inch pipe, and I want to use either a similar system as used in the video except with a slip plug or [what I would prefer] using a solid rod of pvc or Delrin [or something else similar] and then machining in the grooves for the O rings. I would imagine I need to get something like a 3.25 solid rod, put in my grooves, then have an inner diameter 3.25 pvc pipe, then use that as a “lock” for the o-rings, and that would add .5 to the total outer diameter, and the o-rings would stick out the rest of the .25 inches, and compress and act as the watertight seal.

So, since I do like to ramble, my questions are –
How would I make a watertight o-ring based piston head for a pvc 4 inch pipe so that it can still move and keeps water on one end?
How many o-rings should I use when making the piston head so that I avoid water movement [I was thinking of using 2-4, but I’m afraid that it is going to end up with water stuck between the o-rings. ]?