| ARTICLE - Choosing a Pump | ||
Choosing a Pump
A pump for a statue or fountain spray takes less volume of water than a waterfall. Many fountains or statues work well with 700 gallons per hour or less, and several will perform nicely with as little as 300 gallons per hour or less. You must filter the water when operating something with small openings like the fountain or statue. Clogging from small particles will occur without filtration. If the pump is to be used for recirculation only, with no visible water flow, then the pump is usually chosen according to the pond size. A good rule of thumb is to recirculate the entire pond volume once every one to three hours. Move the water from one end of the pond to the other using tubing attached to the pump. Hide the tubing in the stonework around the pond and discharge the water as far from the pump as possible. A waterfall requires much more water than other uses. To be visually effective and to fall cleanly from one layer of stone to the next, a flow of 100 - 200 gallons of water per hour per inch of waterfall width is necessary. Any less than 100 gallons per hour per inch is not a very effective flow. Don't be afraid to go up to 200 gallons per inch; it sounds like a lot, but it makes a beautiful waterfall. Just make sure the sides of the waterfall or streambed can contain the flow. More water can create a very effective display. Figure out what you want to the falls to look like, in other words decide how wide the flow is to be between the stonework. Try to decide on a number for the average width when calculating flow rate. The outlet height is determined by measuring the vertical lift. Measure from the pond surface to the top of the spillway vertically. Measure the length of pipe or tubing you will need to go from the pump to the top of the waterfall outlet. Divide that measurement by 10. This number is added to the vertical lift to get a total lift that is used in selecting your pump. This total lift can be matched to the pump charts to choose the correct flow rate for your spillways. Be sure to maintain a flow rate of 100 - 200 gallons or more per inch of spillway at the total outlet height. Volume is more desirable than pressure in disguising the flow of water into the top spillway. Use an adapter or bushing to make the connection to larger tubing than the actual outlet size (In other words, if the pump has a 1" outlet, you should have a 1-1/4" or larger tubing size). This eliminates pressure while maintaining volume. Determine the length of tubing by measuring the depth of the pond, the distance from the pump (or skimmer) to the point the water is put back into the falls or upper pond. Remember to allow extra length for underground obstacles and curves. Use the pump flow charts in the catalog to choose the correct pump. Our method of choosing a pump: 1. Width of waterfall desired in inches X 100-200 gallons per hour = Flow Rate. 2. Calculate the total lift by finding the height of the falls above the pond surface(in feet) + the distance of the tubing from the pump to the top of the falls (in feet ÷ 10) = Total Lift. Total Lift = Head Height EXAMPLE: waterfall width desired averages 18 inches wide. This means a minimum of 1800-3600 gallons of water per hour (GPH) is needed. The falls are about 5 feet above the pond. The tubing will be about twenty feet in length once it comes out of the pond and curves around shrubs on it's way to the top. Convert tubing length by dividing by ten and add this number to the height above the pond [or 5' + (20' ÷ 10) = 7']. This number is the total lift. You now know you need a minimum of 1800-3600 gallons per hour (GPH) at 7' of lift. Look on the pump charts provided to find which pump will give you the flow of water at the height that you determined earlier. Look also at electrical use, warranty period and quality of product in making a final decision on the pump purchase. Do You Want to Calculate Your Pond Volume?
One cubic foot of water equals seven and a half gallons. To find the cubic feet of your pond, multiply the length (in feet) X the width in feet X the depth in feet X 7.5 = gallons of water. You'll have to adjust for an irregular-shaped pond, but this is a starting point.
Calculating Electrical Cost
Pumps have plates that show the manufacturers rating for amps and watts. The watts are multiplied by 24 hours to give you the total number of watts used in a full day. Divide the watts used in a 24-hour period by 1000. This gives you the kilowatt-hours used in one day. Your electricity bill tells you how much you pay for a kilowatt-hour. Multiply the cost per kilowatt-hour by the kilowatts used. This gives you the cost per day. Example: A 150 watt pump operating 24 hours a day at 10 cents per kilowatt hour is calculated as follows: 150 Watts X 24 Hours ÷ 1000 X 10 cents = $0.36 per day.
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