How To Use Sump Pump Performance Curve

Step 1: Make note of the two axis found on the curve. One axis is labeled "FLOW PER MINUTE" or hour. This tells us how much water the pump can remove from the basin during the stated amount of time. The other axis is labeled "TOTAL DYNAMIC HEAD". This tells us how much water can be removed from the basin even though the flow is slowed down by vertical lift height, check valves and elbows.

Step 2: Measure the vertical distance of discharge pipe from the sump pump port to the highest vertical height of your existing sump pump system. Add 2 or 3 feet to accomodate the friction pressure caused by a check valve and two or more elbows located within the vertical height. This distance approximates the Total Head Height or your system.

Step 3: Take the manufacturers Pump Performance Curve and find your total dynamic head height. Usually it will be around 10 feet. Find the point where the Total Dynamic Head Height and Flow per Minute (some charts show Flow per Hour) intersect. This intersection point tells you how much water a specific pump model will remove from the pit during the specified time period.

Step 4: Determine how much water must be removed from your basin during a heavy rainstorm per pumping frequency. This can be done in one of two ways.

Option a:Place the end of a yardstick on the bottom of the basin. Note how many inches it is to the bottom of the float in OFF position. Measure the diamenter of the basin. Then measure the height of water on the yardstick when the pump motor starts running. Subtract the difference between the bottom of the float height and the height when the motor runs. For an eighteen-inch basin, each inch of height equals one gallon of water. For a twenty-four-inch basin, each inch of height equals two gallons of water.

Option b:Find the ON OFF point for your existing model in the manufacturers specifications. Monitor how much time passes between each ON pump cycle. For example, if the specifications state the ON Position to be 9 inches and the off position to be 4 inches. The difference is 5 inches. In an eighteen-inch diameter pit 5 inches equals 5 gallons of water.

Step 5: Note if your existing sump pump can keep up with the water flow. If not, use the gallons of water from step 4 to determine how much pump performance is required for your water pumping needs.

Step 6: Include the time factor. How many seconds or minutes lapse between each pumping? Let 's say it is 5 seconds. So if your distance in step 4 was 5 inches and the motor runs every 5 seconds, that means 5 gallons of water must be removed every 5 seconds or 60 gallons of water must be removed from the pit every minute.

Most manufacturers measure pump performance by gallons pumped per minute (GPM); however some use gallons pumped per hour (GPH). If the pump performance is over 100, the results are probably shown in GPH. Simply divide the GPH by 60 to obtain the GPM.

Generally the greater the horse power the greater the pumping capacity; however there are some 1/2 horse power motors that can pump as much as 3/4 HP motors.

If your sump pump runs even when there is no rain, it is wise to consider buying a manual pump and a float switch that is not attached to the pump. The Zoeller variable level float switches and the HC6000 electronic switch are great options because the distance between the ON OFF point can be increased which prevents the motor from runnning so much.

Make certain you know the volume of water flowing through your pit. This will enable you to buy the right sized pump.

Cast iron pumps are best suited for heavy volume pumping. Cast iron adds weight for less pump-movement and does not warp or crack like thermoplastic.

Each pumping cycle causes wear and tear on the float switch. No float switch will last as long as a cast-iron housed pump. Therefore it is important to replace the float switch every three to five years. Two-poled, magnetic and definately electronic switches last longest.

Maximum head height is the distance at which the pump will no longer operate. As mentioned previously, check valves and elbows do add friction and therefore reduce pumping ability by 2 - 3 feet. Horizontal distance can also be a factor if the angle of the pipe is not sloped down toward the location where the water is pushed to it desired location.

Generally the maximum head height will not be reached; however it is true that the greater the maximum head height capability, the greater the pumping performance at lower vertical heights; therefore, if the water volume entering the pit is high, a sump pump with greater maximum head height will perform better than one with a lower maximum head height.