Guide to Sizing Pumps

Guide to Sizing a Pond Pump

1. Determine the volume of a circular pond by measuring the diameter of the pond at its widest part and depth at its deepest part. Multiply the diameter by 2, then by the depth, then by 5.9. For instance a circular pond with a diameter of 11 feet and a depth of 5 feet would have a volume of about 3,570 gallons (diameter x 2 x depth x 5.9 = volume in gallons). 2. Calculate a square or rectangular pond’s volume by measuring in feet and multiplying the length by the width by the depth measured at the deepest part by 7.5. For example, a pond that is 12 feet long, 11 feet wide and 5 feet deep would be about 4,950 gallons in volume (length x width x depth x 7.5 = volume in gallons). 3. Calculate the volume of an oval-shaped pond by measuring the length at its longest part, the width at the widest part and the depth at the deepest part. Multiply the length by the width by the depth by 6.7 to determine the volume. For instance, an ovular pond that is 11 feet long, 7 feet wide and 5 feet deep would have a volume of about 2,580 gallons (length x width x depth x 6.7 = volume in gallons).

Tsurumi’s Guide to Sizing a Waterfall Pump

1. Measure the waterfall weir, which is the width of the water across the top of the fall. Round up to the nearest foot. 2. Measure the height of the waterfall from the weir to the surface of the water where the fall hits. This is called the head. The head is the amount of mechanical or gravitational resistance the pump will have to overcome. If you have 90-degree angles in your tubing, add 1 foot of head for every one to two turns. Add 1 foot of head for every four fittings or adapters in the tubing. Add 1 foot of head for every 10 feet of tubing between the pump and the fall after the initial 10 feet. 3. Multiply the length of the weir by 1,500 gph for a medium flow — about a 1/2-inch curtain. Use 1,000 gph for a lighter flow or 2,000 gph for a heavier flow. Look for a pump that will move the correct number of gallons at your waterfall’s head height. For example, a 3-foot weir requires a 4,500-gph pump. If the pump is rated in gallons per minute, divide the gph by 60. A 4,500-gph pump is equivalent to a 75-gpm pump. If the waterfall is 5 feet high with 2- feet of tubing and three turns, get a pump rated for 4,500 gph at 8 feet of head.

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