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Falls Flow

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Ever wonder how much water is flowing over a waterfall? Need to make sure you buy the right size pump for a fountain? Curious how much water is draining into a storm sewer? Bored at the mall and curious how much water is running around? Use this extremely simple app to estimate how much water is flowing over the edge of your waterfall.

You simply measure how wide the waterfall's edge is, and how deep the water is just before going over the edge, and you can get a close number. This app will report the value in gallons per minute, pounds per hour (for water only), and barrels per day.

The same values can be used for other liquids if you are measuring something else (e.g. brine, oil, alcohol, etc...)--BUT--the pounds per hour value will not be correct if it's not water. Using this for viscous fluids (e.g. syrup, molasses, waxy liquids, etc...) is not recommended as the height of liquid will be higher for low flows and this correlation will not likely work.

Chemical engineers can use this app for quick estimations in the field for flow over weirs, like storm water drains, overflow weirs for any type of container, testing flow for tray flow testing over weirs, estimating crest height over a weir (if you already know the flow, change the height until you get the flow, like for tray weir flows). Having problems with a gas-liquid separator, ensure that the crest height over your overflow weir is not too high and decreasing your vapor/liquid separation area of your drum too much using this quick and easy tool.

For circular fountains, you can simply enter the "Width" of the rectangular falls to be the circumference of your circle (measure the diameter of your fountain, and multiply by 3.14, you'll be close).

Testimony: I have used this in the field for calculating the dump cycle of coalescers to a pit with an overflow weir, then checked the result, bought a pump (over $30,000 for a 250 gpm pump), and it worked great. This was a much easier calculation than calculating the gravity drainage pressure drop versus flow for the drainage piping to the dump pit. The pump was intentionally oversized by less than 10% (which for engineering is great) and it did not cycle on/off like the operations and maintenance folks feared. Dump cycle duration was 15-20 minutes, with no pump cycling on/off. A great success.

Tips to measuring for small systems: 1) Be as accurate as possible. 2) Take several measurements of depth along the entire width (e.g., one in the middle, a couple of measurements closer to the side of your opening). 3) Use a ruler with very detailed tick marks on it--the slightest 1/8" error can cause big changes in your result. 4) Take the height measurement of water at least 1" from the edge if possible, and if you can back it up even more than that, I recommend being away from the edge of the falls at least twice the height of the liquid that you are measuring.

Tips for measuring larger systems: Don't get in the water, to measure, you could get thrown over.

See the screenshot pics--a simple illustration shows you what to measure, and allows you to input the measurement in feet and inches (separately).