Pump horsepower, as well as fountain flow rates, are often stated in deceptive ways.
You see, pump horsepower can be rated by input horsepower and output horsepower. Input horsepower is calculated by the electrical energy going into the pump, whereas output horsepower takes into consideration the pump’s efficiency. Many if not most of the advertisements of pump horsepower ratings found online are posting input horsepower instead of output horsepower, which is what is important to the consumer. Often enough, output horsepower is three times less than input horsepower.
When it comes to aeration, the actual flow rate of a pump is what is most important. Decorative pond fountains, which use pump impellers and nozzles to create displays, have lower flow rates than aerating pond fountains, which use propellers instead of impellers and no nozzle to obstruct the flow. Plain aerators have the most flow of all three, but create almost no display at all.
Though the flow rate of the pump is important, the measure that is concerned with aeration is known as the “evacuative flow rate.”
Kasco fountains and aerators are measured using evacuative testing (catching all the water thrown past the propeller or nozzle and then measuring it). This is the most accurate method for knowing the true flow rate, which is what will determine the amount of aeration achieved. The more water “thrown” into the air, the higher the aeration will be.
To obtain very tall displays, often the display patterns of some manufacturers severely restrict the flow of water, as the nozzle holes are skinny and the patterns are wispy, thus resulting in an interruption in the display pattern in windy conditions.
We know this gets kind of technical for the average consumer, but you can tell a lot by looking at pictures of fountain displays, e.g., if the displays appear to be created by thick or thin streams of water. You can see thick streams of water in the Kasco nozzle pattern on this page.