It's a bit more than 20 feet (that was just an example). However, with a 48-inch pipe that's quite a bit of area. 8.67 psi is 1,250 lbs per square foot. I had a pipe manufacturer verify and I was using the correct formula. It surprised me too.
I pulled the 20 feet as an example. The conditions are in that general range though.
It's a 48-inch pipe. Whether or not schedule 40 is applicable to that size is one of the contractual issues and 1/4" thick pipe is proposed in the absence of a defendable "schedule 40 standard".
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I'm reviewing a shop drawing from a tank builder which includes a vertical overflow pipe internal to the tank. The pipe will be empty and subjected to varying levels of external hydrostatic pressure varying from 0 feet to, say 20 feet at the bottom of the pipe as the water reaches the overflow...
