Waterfall Pump Calculator
Enter your spillway width and head height to find the pump flow you need for your waterfall. You get the gallons per hour needed at the top of the falls plus the pump maximum rating to shop for, so the water still arrives strong after head loss.
The width of the lip where water pours over the top of your falls.
The vertical rise from the pump up to the top of the waterfall.
How much water you want pouring over each foot of width.
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GPH at the top
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pump max rating
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GPH per foot
How to use this: you need about GPH actually arriving at the top of the falls. Because pumps lose flow with height, shop for a pump rated near GPH maximum, then read its flow-vs-head curve to confirm it still delivers your target flow at ft of head.
Right-sized gear for your waterfall
Auto-matched to your flow. Sizes are starting points; always check the pump's head curve.
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How to Size a Waterfall Pump
A waterfall pump has one job: deliver enough water over the top of your falls to create the look you want. The amount you need is set by two things, the width of the spillway where the water pours over, and how heavy a sheet of water you want flowing across it. The common starting point is 1,000 to 2,000 gallons per hour for every foot of spillway width. A gentle trickle uses roughly 1,000 GPH per foot, an average sheet uses about 1,500, and a strong full sheet that completely covers the lip uses 2,000 or more. The calculator above turns your spillway width in inches into feet, multiplies by the per-foot figure for your chosen style, and gives you the flow you actually need at the top of the falls.
Why Head Height Changes Everything
Here is the part that trips up most first-time pond builders. The gallons per hour printed on a pump box is usually the flow at zero lift, with the outlet at the same level as the pump. Real waterfalls sit above the pump, and every foot of vertical rise from the pump up to the lip of the falls steals flow. This vertical distance is called head height or lift. A pump that moves 3,000 GPH at zero feet might only push 2,400 at 4 feet and 1,800 at 8 feet. So if you need 3,000 GPH arriving at the top of a waterfall that climbs 4 feet, a pump rated for exactly 3,000 GPH will fall short. You have to buy a pump whose maximum rating is higher, so that after the loss it still delivers your target.
The calculator handles this with a rough head-loss buffer, adding about 12 percent more required flow for every foot of head height. That gives you a sensible pump maximum rating to shop for. It is a planning estimate, not a replacement for the manufacturer's data. Every quality pond pump publishes a flow-vs-head curve, sometimes called a performance curve or a flow chart. Find your head height on that chart and read across to the real flow at that height. Buy the pump that still hits your target at your head, and you will never be disappointed by a weak trickle where you wanted a sheet.
Wider and Taller Falls Need Much Bigger Pumps
It is worth being honest about scale before you buy. Flow needs grow quickly with both width and height. A modest 12 inch spillway with an average sheet wants about 1,500 GPH. Double that to a 24 inch spillway and you need roughly 3,000 GPH at the top, and once you account for a few feet of head you are shopping for a pump rated around 4,000 GPH. Go wider or taller still and you climb toward 5,000 or 6,000 GPH. Those big pumps cost more up front, but the bigger issue is energy. A pond pump typically runs 24 hours a day, so an oversized pump quietly adds to your power bill every month of the year. Size the pump to the waterfall you actually want, look for energy-efficient or magnetic-drive models, and resist the urge to buy the biggest pump on the shelf just in case.
One Pump or Two?
Many ponds run a single pump that pushes water through the filter and out over the waterfall in one tidy loop. That works well as long as the pump moves enough to both turn the whole pond over at least once per hour and feed the waterfall at your target flow. When you add those two needs together and the total gets very large, some keepers split the work, using a dedicated waterfall pump alongside the main circulation pump. Either way, start with your pond volume to set the circulation requirement, then layer the waterfall flow on top. Our pond pump calculator sizes the main circulation pump from your gallons, and the pond volume calculator gives you those gallons in the first place.
Keep going: size the rest of your pond.
Frequently Asked Questions
How many gallons per hour does my waterfall need?
A common rule of thumb is 1,000 to 2,000 gallons per hour for every foot of spillway width, measured at the TOP of the falls. A gentle trickle wants around 1,000 GPH per foot, an average sheet of water wants about 1,500, and a strong full sheet wants 2,000 or more. So a 24 inch wide spillway, which is 2 feet, at an average sheet needs roughly 3,000 GPH actually arriving at the top of the waterfall.
Why is head height so important when sizing a pump?
Pumps lose flow as they push water higher. The vertical rise from the pump up to the lip of your waterfall is called head height, and every foot of it cuts into the gallons per hour the pump actually delivers. A pump rated for 3,000 GPH at zero feet might only move 2,000 GPH once it has climbed 5 feet. That is why you size for the flow you need AT the top, then choose a pump whose maximum rating is higher to cover the loss.
What is a pump flow-vs-head curve and how do I read it?
Every quality pond pump lists a performance curve or table showing gallons per hour at different lift heights, often labeled as head, lift, or max head. Find your head height in feet on the chart, then read across to see the real flow at that height. Choose a pump that still delivers your target GPH at your specific head height, not just at zero feet. If the box only shows a single big GPH number with no curve, treat that number as optimistic.
Do wider and taller waterfalls really need much bigger pumps?
Yes, and the jump is bigger than most people expect. Flow scales with spillway width, so doubling the width roughly doubles the GPH you need. Height adds even more because taller falls mean more head loss, so the pump has to be rated higher just to deliver the same flow at the top. A tall, wide waterfall can easily call for a 4,000 to 6,000 GPH pump, which also means a noticeably larger electric bill to run it around the clock.
Will a bigger waterfall pump cost a lot more to run?
Energy use is the real long-term cost of a waterfall. A pump runs 24 hours a day in most ponds, so a high-flow pump can add a meaningful amount to your power bill each month. Look for energy-efficient or magnetic-drive pumps, size the pump to your actual spillway rather than oversizing, and consider running the falls only during the day if your pond has separate aeration. A right-sized pump saves money every single month it runs.
Can one pump run both my waterfall and my filter?
Often yes, and many ponds do exactly that by running the pump through the filter and out over the waterfall in one loop. The key is that the single pump must move enough water to both turn the whole pond over at least once per hour AND feed the waterfall at your target flow. Add those needs together when you size it. If the combined number is very high, some keepers run a dedicated waterfall pump separate from the main circulation pump.
How wide should my waterfall spillway be?
Spillway width is a design choice that sets the look of your falls and the pump you will need. A narrow 6 to 12 inch spillway makes a focused, gurgling stream and sips power. A wide 18 to 36 inch spillway makes a dramatic sheet of water but demands far more flow and a bigger pump. Pick the width first based on the look you want, then use the calculator above to size the pump to match it.