Pond Boss Forums POND CONSTRUCTION Selecting a site 12" schedule 40 PVC Siphon System Failure

Lassig,

How big will your pond be and how many inches of water do you expect to run through the siphon system before the water flows through your emergancy spillway?

When I built my 4 acre pond, I went with a 6 inch drain line that will also act as a primary overflow. In the two plus years that my pond has been full, I've realized that it's too small to do anything as an overflow. I still like the ability to drain the pond and lower the level of the water, but that's all it's good for.

A simple, basic rule of thumb on pipe sizing is that for every half inch bigger that the diameter of the pipe, you get twice as much volume that will flow through it. A one inch pipe will carry twice as much water as a half inch. Every half inch doubles the volume. So a two inch pipe will carry four times as much water as a one inch pipe.

The 12 inch pipe will carry a massive amount of water. The math is too much for me to figure and I have my doubts that this half inch rule still applies from six to 12 inch pipes.

If you want a siphon system, you will either have to have a huge difference between your pipe height and your spillway height, or a very small pond.

Good luck,
Eddie

Looks like I will have both situations. The planned size for my pond is 3/4 to 1 acre and the planned distance from siphon to emergency spillway is 2'. I have barely over 10 acres that drain into this pond so the NRCS and builder of it beleive the emergency will never be used. But you know what they say about never.

lassig, thanks for the drawings. That is very useful. I just made a siphon for my 3/4 acre pond out of 3 inch to lower it about 2 ft. I figure a ft. a day. I will place one permanently thru the dam when they come to fix the back side of the dam. We had 6 inches over 3 days, followed by 5 inches in a few hrs. and that caused the overflow. Eddie, as far as size of pipe vs. volume; assuming same length of suction side, the volume is proportional to the square of the radius.

12 inch 6x6=36
6 inch 3x3=9
4 inch 2x2=4
2 inch 1x1=1
1 inch 1/2x1/2=1/4

so 12 inch carries 4x volume than 6 inch
4 inch carries 4x volume than 2 inch
2 inch carries 4x volume than 1 inch.

probably useless info, but someone may can use it.