Originally Posted By: hawgtusks
Its easy to calculate the pressure at the outlet...
Just multiply the depth of the intake (in feet) by 62.4 pounds per cubic feet. There will be some minimal headloss (pressure loss) through that short section of pipe and the couple of angles that the water must traverse, but those are negligible and should just be disregarded for the purposes you are concerned with.

If the "flood stage" is 5 feet above the normal water level, your pressure at the outlet would be (13'+5')x62.4 pcf = 1123 pounds per square foot (divide by 144 to get about 8 pounds per square inch). So, a cap on a 12 inch pipe would have to resist 1123 psf X 3.14159 X 0.5 X 0.5 = about 882 pounds of pressure.


In my opinion, it would be much easier to just extend that pipe 5 feet vertically, or however much higher you want to maintain the pond level, than it would be to try to cap the pipe and have to worry about it springing a leak under the pressure of 13 feet + flood stage water elevation of water. The extension would just have to be able to handle the thrust resulting from the water rushing through. A good weld and maybe a small supporting framework for the additional pipe length should easily handle this.


Thanks Hawgtusks, that's just the equation I was using to do the math, hahahaha! I guess I was wrong. I thought the pressure would be much less. Thanks for making quick work of this and giving me the info I need to make the decision....to simply extend the pipe instead of capping it.

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