While I am still waiting for the flow meter, I did some rough estimate to check the flow rate of the pumps. I have two Aquascape Biofalls. The fall height is about 3 feet and with 20 feet 2" pipe, I would estimate the equivalent head height is about 5 feet. I am using one Aquasurge 5000 (~280 Watts) and the other is Malata Versiflow v-3900 (~400 Watts). The Wattage are measured with Kill-A-Watt P4400.
I measured the flow rate as follows. I drained the biofall and then put a wood ruler into it to monitor the water level. After turning the pumps on, I waited the water level reach about 6" below the waterfall level and started stopwatch. Once the water level is 6" higher, I stopped the stopwatch. It took the v3900 17 seconds and the 20 seconds for the Aquasurge 5000 to fill this 6" height.
I measured the Aquascape biofall's average water surface area is about 650 inch^2 for my measurement. The total volume filled during my measurement is about 3900 inch^3 or about 17 Gallons. Thus, the flow rates calculated based on the measurements are 3600 gph for v3900 and 3060 for the Aquasurge 5000.
These results may not accurate and I will validate them once I received the flow meter. However, they do provide some rough estimate and can be done with no special equipment. Thus, I feel the rated flowrate of the v3900 is right on target but the Aquasurge 5000 is highly over rated.
My conclusion is that my previous observations about the low flow rate Aquasurge 5000 and Pondmaster Pro Hy-Drive 4800 were correct. However, the cause may not be due to low head height as I claimed before. The real cause is that these "evergy efficient" pumps do not meet their own specification on flow vs. headheight, e.g., Aquasurge 5000 should provide 4200 gph at 5' headheight according to their specification. (If my results are correct, their claims are very misleading to say the least.)
I would really appreciate if others can comment on my methodology and conclusions and maybe verify my results if you have interest and time to do so..
