what ever phappened to 'pi' x R^2 ? I am confused
This has to be my last post for the next three weeks

And it has to be incomplete
(I'd stick around but I am really torn between sitting in front of the computer vs. going fishing on the Canadian border. I am hoping for a small musky or Northern Pike to follow me home

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The pi r^2 formula is still around. I just simplified it to use on the most basic calculators. And to use the diameter instead of the radius, less math is involved.

Another tip to simplify math is to only use two or three decimal places in your calculations. Pi really only needs to be 3.14 because you really can't measure a hundreth of an inch with a ruler. I used a caliper to measure the pipes which was really an overkill because the same pipe from the same factory made at a different time will have allowable tollerances of more than one hundreth of an inch. To use pi or any other calculation to twelve significant figures implies that it is possible to measure a hydrogen atom with a ruler. Just a weird bit of trivia. I had to have this explained to me too
Oops, I am babbling about entertaining stuff (to us nerdy folk) instead of helping with the math, etc. And time is a wastin'. Hmmm, had to re-read your post to see what I was suppose to respond to...I guess that was it, right? I am operating on zero sleep so details are getting the best of me right now.
Oh yeah, the pipe measurements are never what they want you to think they are...for some odd reason. My 1.5 inch pipe was a little light on the plastic (but better for flow). It measured 1.6 inches inside diameter. It is really splitting hairs, I just added that for trivia and some head scratching. The OD of the 3/4 in pipe measured out at 1.05 inches...the five hundreths would be hard to detect using a ruler. It is that allowable tollerance thing again. Splitting hairs, I know.
and for the kicker

(that is me laughing at myself) I screwed up on the math! Feel free to laugh with me...or at me

I entered [(D^2) x pi]/4 instead of (D^2) x pi/4 and didn't check how the calculator translated how I entered it. (That Order of Operations thing.) That's what I get for not using the .785 formula...me and my stupid calclulator (Doh!!!) (extra L in calculator was a mistake, but maybe I need to get a clue

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And I guess I will have to wait three weeks for the sump design. I am tossing ideas around to fit limited space. I am really close to drilling holes in the wall. The hammer drill is already in positon waiting for me.
Also, if this helps, I do my R&D outside with buckets on ladders, and the PVC pressed together without glue. Leakage is minimal and you can make changes on the fly.