How to Determine the Size of Waterfall Pump You Need:
Want a waterfall feature and don't know how to figure out what size of pump you'll need? Here's some quick, basic information. (Our pond construction ebook has more comprehensive information.)
First, you will need to determine how wide your waterfall weir is. (A weir is the area where the water is actually falling down.)If your waterfall weir is 36 inches across, you will use 36 inches for part of this equation.
Now, for every inch wide your waterfall weir is, you will calculate using 100 - 150 gallons per hour for your waterfall pump size. If you want a nice, steady flow you may use around 125 GPH or so. If you want a 'Niagara Falls' look, you may use around 150 - 200 GPH. Multiply every inch by what type of look you want. In this case, a nice flow of 125 GPH x 36 inches. This equals to a 4,500 GPH waterfall pump but - there's more and this is where most people make the mistake of getting the wrong size of pump.
You also need to work in the length and height the waterfall pump will need to push water. Afterall, the distance you want it to push water and the height will greatly affect what size you need - and, you want to make sure the pump is big enough to have the look you want.
So, you need to measure - not just eyeball it, but measure the distance the pump will be in your pond up to the waterfall weir. This measurement is your length and would also be the length of tubing you need.
Next, you'll need to measure the height from the top of the POND water to the top of the waterfall weir.This height is called a 'lift' in pump terminology. (Don't measure how deep the pond, only from the surface of the pond.)
Now, for every foot of height the water has to be pushed from the top of the pond water, we calculate one foot of 'lift'. Let's say that your waterfall weir is 4' higher than the top of the pond water below. We would use a 4' lift into our equation, but --- yes, there's more!
We also have to add one foot of lift for every 10 FEET in horizontal length the waterfall pump has to push water. In our example, let's say that we need to push the water 30 feet from the pump to the top of the waterfall. We divide the 30 feet by 10 feet and we get 3 feet of lift.
Lastly, we add up the lifts. We had a 4 foot lift in height and we had a 3 foot lift in length and this gives us 7 feet of lift.
The magical part is where we put this altogether. In our beautiful (wink, wink) waterfall example, we would need a waterfall pump that pumps 4500 GPH at a 7 foot lift. What this means is that we need to find a pump that will pump that much at that given lift. It DOESN'T mean that it's a 4500 GPH pump - and that's it. This is extremely important you understand this; if not, you'll get a pump that is way too small and you may have a drizzle or no water pressure at your waterfall instead of the nice flow that you want. And, here you would have gotten all of the tubing, had electricity installed, gotten the pump and used it and bam! It's not the waterfall you wanted. Another bad thing is the fact that the pumps aren't returnable because you would have put it in potentially scummy water and no one wants to buy your returned waterfall pump. So, it's important that you figure this out correctly.
A HUGE TIP: When you shop for a waterfall on our website or if you were having an off moment (grin), and were looking for one somewhere else - you have to look at the chart on the pump box to tell you what that waterfall pump will perform at different lifts. In our case, you DO NOT want to look for a box that says it's a 4500GPH pump because this number is most likely at a 0 foot lift or a 1 foot lift - not a 7 foot lift that you need. So, look at the chart and see what that pump will perform at 7 foot lift. It might be only 2400 GPH, it might be 1200, it might be 4200 GPH. You don't know until you look at the chart.
Another important tip is that waterfall pumps start to use Gallons per Minute or GPM instead of Gallons Per Hour or GPH. You'll need to figure out how to calculate for this difference. We have that and a whole lot more information in our pond construction ebook.
If you're baffled about waterfall lifts, think of it as an amount of pressure needed to go against friction and gravity.These are referred to as our horizontal and vertical lifts.
If you're puzzled at why we only add one foot of lift for every ten feet horizontal distance while we add one foot for every foot in vertical distance, it's because it would take less pressure for your waterfall pump to push water horizontally than it would need to push it against gravity and go vertically up to the waterfall.
Taking the time to correctly figure out what size of waterfall pump you need is worth every effort spent. If the pump is too small, you may have no waterfall at all because the pump wasn't strong enough. If the waterfall pump is too large, you could have too much pressure for the size of waterfall unit you have and the water will flow over the sides instead of off the front of the waterfall unit and be a huge mess.
As always, if you need any help determining what size of waterfall pump you need, we're happy to help.
~~~~~
Have you found this article useful? Please like us on our new Facebook page. We also have a new Pond Solutions mobile app.