The right pump can be a crucial part of a garden pond’s ecosystem. By circulating the water in your pond, a pump helps keep fish healthy by maintaining safe levels of dissolved oxygen. Keeping the water moving also helps to promote aeration and nutrients throughout the pond and discourages the growth of pests like mosquitos and algae. Equipment like filters, waterfalls, and fountains each need specifically sized pumps to function well.
Most pumps are either submersible, meaning they sit on the bottom of the pond, or external, meaning they’re positioned above the water line. Pumps come in a variety of sizes and strengths, and the type you choose should depend on what you need it for. You wouldn’t use the same engine to power a diesel truck and a compact car. In the same way, you’d need a different pump to circulate water in a large, heavily stocked pond than you would to supply a small waterfall.
To size a pump, you need to consider two important numbers: flow rate and head. Together, they tell you how much water a pump can move and how much resistance it can overcome.
Pump Head vs Flow Rate – What’s The Difference? (Flow Definitions)
1) Flow Rate & Head Height
The first step in sizing a pump is finding the flow rate you need. Flow rate refers to the volume of water moved per unit of time. Depending on where you live, flow rate is usually given in gallons per hour (GPH) or liters per hour (LPH). The more energy your pump can supply, the more water it can move at one time.
Once you know the flow rate you need, the next step is to estimate your setup’s head height. Pumps don’t supply the same flow rate in every situation. Instead, a pump’s flow rate varies based on a quantity called head height, or just head. Head is an engineering term that refers to the height at which a pump lifts water above the surface of a pond. As head increases, a pump’s flow rate decreases. That’s because the higher the water travels, the more gravity and friction resist its flow. Stronger pumps can supply larger flow rates at higher amounts of head. Your pump should provide your desired flow rate at your system’s head height.
2) Total Dynamic Head (TDH) & Friction Head
The overall head height of a pond configuration is called its Total Dynamic Head (TDH). Precise TDH calculations are fairly complicated and can involve a lot of variables. In terms of a backyard pond, though, it’s easy to simplify. Every foot of vertical distance between the surface of the pond and the highest point the water is pumped to counts as 1 foot of head. This distance is sometimes called static head.
True TDH calculations can also involve friction head and pressure head. Friction head describes how pipe size and material affect resistance to flow. Friction head usually doesn’t make a big difference for garden ponds, and a detailed explanation is beyond the scope of this article. Still, there are a couple of easy ways that all pond owners can limit friction head. When choosing a pump, always plan to use the manufacturer’s suggested pipe size. Smaller pipes mean less room for water and therefore less flow rate. Using a thinner pipe is a waste of your pump’s power and can even damage certain setups. You can also account for friction by adding 1 foot of head for every 10 feet of horizontal piping between the pump and your filter or feature. Every 90° turn in the piping contributes 1 foot of head as well. For more exact calculations, you can use a friction loss chart. Keep in mind that these are often intended for professional landscapers.
3) Pressure Head & Max Head
Pressure head is the resistance from devices that use pressure to operate. You may need to include pressure head if your pump is going to power a pressurized filter, UV light, or spray nozzle. (Pressure head is easy to estimate, but if you happen to know a device’s actual pressure, you can calculate it exactly using the conversion factor 2.31 feet = 1 psi.)
After adding up all your sources of head, you’ll need to find a pump that supplies the right flow rate at that height. If you need 3,000 GPH at 10 feet of head, a pump that can give only you that flow rate at 5 feet won’t be strong enough. Manufacturers usually list the flow rates their pumps provide at several head heights. One of these will be the max head height, which is the furthest distance a pump can lift water. At the max head height, the flow rate is basically zero. You can use pumps’ max head heights to compare how strong they are.
These general guidelines are useful for understanding what flow rate and head height can tell you about a pump. The next step is applying them to your particular setup. Below, we’ve laid out some specific details about sizing pumps for water features, and for filtration and circulation.
What Size Pump For Water Features?
The size of your pump directly affects the appearance of water features like fountains and waterfalls. For simplicity, we’ll stick to setups where the water feature is the only thing connected to the pump. If you want to include other components, like extra filters, you’ll need to account for them as well.
For a fountain, the pump’s strength determines how high and forcefully the water climbs. To figure out the flow rate you’ll need, measure the diameter of your fountain’s outlet. For every inch, add 100 GPH to your flow rate.
Next, find your fountain’s head height by measuring the vertical distance from the outlet to the spot where the pump will lie. Remember that if your pump’s max head height equals this distance, the water leaving the fountain will be only a dribble (if that!). A pump with a max head height that’s about 1.5 times greater than this distance can supply a healthy stream of water to the top of the fountain. For example, if your fountain’s head height is 22 inches and its outlet diameter is 3 inches, you’ll want a pump that provides at least 300 GPH (3 * 100 = 300 GPH) and has a max head height of about 33 to 35 inches (22 * 1.5 = 33).
| Quick Calculation: Fountain |
Flow Rate (in GPH) = (diameter of outlet in inches) x 100 Head Height (in feet or inches) = [(vertical distance from the outlet to the pump) + 0.1 x (length of tubing running horizontally from the pump to the fountain) + number of 90° turns] x 1.5 Example: Flow Rate = 3 x 100 = 300 GPH |
Sizing a pump for a waterfall is similar, but there are a couple of twists. To find the head height, measure the vertical distance from the surface of the water to the top of the waterfall. Remember to add 1 foot of head for every 10 feet of pipe that will connect the pump and waterfall. Next, measure the width of the waterfall where the water will spill over.
To create a moderate flow, look for a pump that supplies a flow rate of 150 GPH for every inch of width. To make the flow gentler, adjust this figure to 100 GPH; to make it more powerful, adjust to 200 GPH per inch. For example, if your waterfall is 20 inches wide, you’ll need a flow rate of about 3,000 GPH for a moderate flow (20 * 150 = 3,000 GPH). If your waterfall is 6 feet tall from the pond surface to the top and is connected with 20 feet of hose, your pump will need to provide that 3,000 GPH at 8 feet of head height (6 + 20/10 = 8 feet).
| Quick Calculation: Waterfall |
| Flow Rate (in GPH) = width of the fall in inches x FS (where FS = flow strength: 100, for gentle flow, 150 for moderate flow, and 200 for heavy flow) Head Height (in feet or inches) = [vertical distance from the pond surface to the top of the waterfall] + [0.1 x length of tubing running horizontally from the pump to the waterfall] + [number of 90° turns] Example: Flow Rate = 12 x 150 = 1,800 GPH |
| Fast Facts: Calculating Flow Rate and Head Height for Fountain and Waterfall Pumps | ||
| Flow Rate | Head Height | |
| Fountain | Flow rate = 100 GPH * every inch of outlet diameter | Pump’s max head height should be 1.5 times greater than the vertical distance from pump to outlet |
| Waterfall | Flow rate = width of the fall in inches multiplied by
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What Size Pump For Fish Ponds?
When sizing a pump for circulation, the most important factors are the volume of your pond and the amount of fish you have. If your pond is densely stocked, your pump should circulate the entire volume of water every hour. That means that if your pond is 1,200 gallons, your pump should supply a flow rate of 1,200 GPH at the head height of the outlet. For ponds with lighter stocks (or no fish at all), pumps that move half the volume may be enough. To estimate volume in gallons, multiply your pond’s length * width * depth * 7.5 (measure in feet for this formula). If your pond is irregularly shaped, use the deepest, widest, and longest points. Too little circulation can hurt your pond’s ecosystem, so it’s usually better to overestimate than underestimate volume.
Flow rate is equally important for pumps powering filters. If the flow is too slow, the filter won’t clean the water fast enough, and water quality will suffer. Conversely, if flow is too fast, there might not be enough time for biological filters and UV clarifiers to effectively process the water. To find the right balance, look for a pump that comes close to, but doesn’t exceed, your filter’s maximum suggested flow rate.
Your filter may also add pressure head to your system. Most pressurized filters add 3 – 5 feet of head. A few models add up to 10 feet, which you’ll usually see in the user manual. UV clarifiers add 1 – 2 feet. Make sure to clean your filter regularly, too. As filters become dirtier or clogged, less water can pass through them, increasing the pressure.
| Quick Calculation: Fish Pond |
Flow Rate* (in GPH) = pond volume (using gallons and feet) = maximum length x width x depth x 7.5 *The flow from your pump should get as close as possible to, but should not exceed, your filter’s maximum flow rate. Head Height (in feet) = [vertical distance from the pond surface to the outlet] + [0.1 x length of any horizontal tubing] + [number of 90° turns] + [filter head (3 – 5 feet for pressurized filters and/or 1 – 2 feet for UV clarifiers)] Example: Flow Rate = 12 x 10 x 4 x 7.5 = 3,600 GPH |
| Fast Facts: Sizing Fish Pond Pumps | |
| Flow Rate |
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| Head Height |
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Pump Size for an Entire System
In most cases, we don’t recommend using a single pump for both a filter and a water feature. There are multiple reasons why it’s better to use separate pumps for these applications. Filters need to run all day, but you might want more freedom to turn off a water feature. Also, many filters can’t handle the flow rates that waterfalls and fountains require. Using separate pumps can save you in energy costs, give you more flexibility, and help to keep water features and filters working well.
Occasionally, though, you may be able to make one pump work for an entire system like this. For those intent on doing this, we’ve provided two formulas, one for a fountain and one for a waterfall below. There are three things to note about these formulas, though:
- These formulas only work for systems with one filter and one water feature. This is because water features release water directly back into the pond, meaning there’s no way to connect more than one along the same path.
- The formulas provide only rough estimates. Your calculation may need additional adjustments depending on your specific situation.
- The formulas don’t account for pond volume. The flow rate you need for your water feature and the flow rate needed to properly circulate the pond water need to match at least somewhat closely. If they don’t, your pond water may not circulate often enough, or your filter and water feature may not function properly.
| Sizing a Pump for an Entire System: Formulas |
| For these calculations: SW = spillway width (in inches) OD = fountain outlet diameter FS = flow strength: 100, for gentle flow, 150 for moderate flow, and 200 for heavy flow D = vertical distance from pond surface to the top of the waterfall L = length of tubing running horizontally from the pump to the waterfall T = number of 90-degree turns in the tubing FH = filter head height: 0 for unpressurized filters, 3 – 5 for pressurized filters, 1 – 2 for UV clarifiers (unless otherwise specified by device manufacturers) |
| Filter + Waterfall: Flow Rate (in GPH) = SW x FS Head Height (in feet) = D + L/10 + T + FH Example: The vertical distance from your pond’s surface to the top of the waterfall (which you decide should have a gentle flow) is 2 feet. The waterfall has a 6-inch spillway and is connected to the pump with 8 feet of horizontal tubing with one 90° turn. Also included in the system are a pressurized filter and a UV clarifier. The manuals for these devices specify that they add 4 feet and 2 feet of extra head, respectively. Flow Rate = 6 x 100 = 600 GPH Head Height = 2 + 8/10 + 1 + 4 + 2 = 9.8 feet |
| Filter + Fountain: Flow Rate (in GPH) = OD x 100 Head Height (in feet) = [D + L/10 + T + FH] x 1.5 Example: Your fountain’s outlet diameter is 3 inches. The horizontal height is 2 feet (24 inches) from pump to outlet. The fountain is connected to the pump by 5 feet (60 inches) of horizontal tubing with one 90° turn. Also included in the system are a pressurized filter and a UV clarifier. The manuals for these devices specify that they add 5 feet and 1 foot of extra head, respectively Flow Rate = 3 x 100 = 300 GPH Head Height = [2 + (5/10) + 1 + 5 + 1] x 1.5 = 14.25 feet (171 inches) |
I have 2-gold fish ponds approx. 100gal each. one is located 2ft higher then the other and 3ft apart. I have a external filter(12”x12”) with 1” supply tube, the supply tube between the ponds is 1”. What size pump do I need ?
Also would like to use the fountain with 1” tube.
Hi Frank,
Could I ask what type of filter box you have (pressurized or non) and at what height the filter is above the water level? Also, would you be using the same pump for both the fountain and filter?
Hi i have a 900mm stainless box waterfall with back inlet its 2ft above the ponds surface i can not work out what size pump i will need for this any help would be great as this is the last thing to do before i get some fish in the pond many thanks lee
Hi Lee,
Sorry for the slow reply! I’d be happy to try to help you here.
A couple of questions – Is this waterfall box also the main filtration box for the pond, or just a water feature? If it’s the main system, could you let me know the rough volume of the pond? Also, is the 900mm measurement you quoted the width of the spillway opening?
Hi, I have a pond kit with a P3 (PE-2F34) pump and wondering what size I can safely build a pond? WxLxD
Thank you
Wonderful explanation. For a slow guy like me ,however, a sample equation that ends up identifying the pump needed would be very helpful.
Example . A man has a small pond 4 foot long by 2 foot wide by 18 inches deep. He wants to put in a waterfall with an 8 inch spillway that sits one foot above the surface of the pond water. on the pond he will have a filtration system that is 8inches by 8 inches by 6 inches deep. the hose to the pond head is 3 foot with one 90 degree turn, He thinks , because he is indecisive, that a moderate flow would be good. Here is the formula for the example and the size pump he needs is a _____GPH
I have a new 2500litre pond in which I would like to keep 5 or 6 koi. Was thinking of buying Fish Mate 15000 pond filter & 9000 pump to ensure good quality water. Is this a good idea or needless overkill and detrimental?
Overkill. I’m sure you’ve done alot of research on that particular filter, but it’s suitable for ponds to 1500 litres (3000 gallons), and puts out a maximum flowrate of 7500 L/H (1500 GPH), used in ponds 15,000 litres (750 – 3000 gallons). It might be too big for your pond. You need a filter that matches the size of your pump. The maximum flow rate of the filter must be equal to, or more than, the maximum flow rate of the pump e.g. If the [filter says 15000LPH then you should use a 6000 gpm pump.
I have a 600 gallon upper pond dumping into a 4000 gallon middle pond and ending up in a 400 gallon lower pond used as my 3000 gpm pump’s home (which I’m going to 6000 gpm soon) I have it pumping into an organic filter.
Hi, I have a 314 litre pond, not yet set up and plan to have a floating water feature fountain – can you tell me what size pump and what do you think about solar pumps please?
Hi I have a 800 gal pond with easypod filter and 6000 litre per hr allpondsolution pump with dual inlet . i have 48-50mm flex pipework , i tried connecting 2nd inlet to oase 40 simmer 50mm pipe but left the hosetails as is so the smallest outlet size.
Skimmer doesn’t seem to work nor the filter. Pump is fine when connected to filter when 2nd inlet is blocked off . What am i doing wrong ? regards Martin
I have a pond that is 11ft x8ft x3ft. x7.5 equals 1980 gal. what size submersible pump should I have or purchase?
Can u pls help what type of pump and filter do I need for a garden pond which is about 14ft in length 7ft wide and 2ft deep.
Hi I am planning to construct a waterfall in my backyard with following configuration
size of ready made pond is 90 gallon/340 litre,
height of fall is around 5′, horizontal distance from pond is 5′
Stream width app 15″ with three fall
could please advise us the Type/capacity of submersible pump, and size of tube
I have a 250 gallon pre formed pond with 3 ,8 inch shubunkins. Im considering buying the Aquagarden 300 5 in 1 kit which has a 5 watt uv bulb included. My gph flow rate is going to be only about 150 since the pond is 18 inches deep and i will be using a fountain with no other features. Customer service at Aquagarden assures thats sufficient. Whats your opinion. Thank you.
I have cubical 460 liter water pond, so what type of filter should I place?
Hi there I have a 7500l pond with about 10 koi and some goldfish. I am running with a Gravity fed Proficlear Premium Drum filter system, a Vitronic 55W UV and pontec pondomax eco 11000 pond pump but the water isnt clearing as good as expected, any suggestions please.
If it’s a new pond, it takes time to balance itself out. By getting organics going, like numerous varieties of water plants, oxygenators works wonders once established. Try putting barley bales in the pond also. you can buy them according to size of how big you need. Adequate oxygen in the water helps keep algae from growing. There’s never one thing but a combinations of ways to get the dense water to clear up. UV’ers never worked good for me
Im fitting a bottom drain to my new pond . What pump do you advise me to use on it?.
I wouldn’t put a bottom drain in a pond. It’ll be a royal pain when it comes to draining it and trying to keep the drain clear of sticks & leaves and leaks are always inevitable. I use my pump to actually syphon the water out when needed.
I have a pond that measures 6x4x2 and have 12 fish in it. What size pump would be the correct one for this.
I’m putting in a 60’x60′ trout pond, with a 12’x12’x20′ deep cooling hole. The water will be pumped from the depth of about 20′ up to a waterfall height of 6′ with 2 outlets one a 2″ pipe the other a 3″ pipe. The distance being pumped is around 40′ with most being vertical draw. What flow rate would be required. Any recommendations on a brand.
Alpine Cyclone Waterfall & Pond Pumps with a 33ft Power Cords, these pumps are wonderful, I leave mine on until its time to take it out for the winter and I’ve had them for up to 3 years. AWhsome pumps!
We moved into a rural house recently with an established pond.It is a rainwater fed natural/man made pond of approx 1500 litre size, stocked with mainly newts and a few frogs and some plants. However, there is no pump! Do you feel there is a need for a pump, as we seem to get a constant build up of blanket weed. There is quite a buildup of rotting leaves in it too. Your advice would be greatly appreciated.
Hi,
We are building a small pond (70litres) with a waterfall/stream going into it. The waterfall is 3ft above the pond and there is 20ft of pipe with two 90 degree turns in it. The width of the waterfall is 8inches. Do you know which size pump?
Need to determine the correct pump size for a fish pond (koi fish) that is 14ft x 14ft x 3.5-4ft in depth = 3.5ft=5145 gal and 4ft=5880 gal. small pond up top that filters down to this main one.
any recommendations on size pump to use and a quality brand. It needs to be a submersible one.
I am putting in a water wheel feature 48″ x 7 inches wide. It is up in the air about 6 to 7 feet. The water will go into a spout directed to make the wheel spin, the water drops into a trough like a miners sluice box and then go down an incline and drop off into a hidden container, which in turn get pumped back about 18 feet up to the spout and again drop into the wheel and start the cycle once again. What size of pump should one use, I am pretty sure a submersible but not sure of the gallon per minute/hour to use. Hopefully you can help me.
Hello.
I need a aquarium/ water fall pump for supplying water to a little creek in a landscape I am going to build. The lifting hight must be min 1,8 m with a water flow low as 150-180 LPH. Can you recommend a suitable pump ?
Thank you this is really so helpful. I didn’t have a clue how to work out what pump I needed for a waterfall, now I’ve worked it out with your easy to understand guide. Much appreciated.
Hi Natalie,
We’re so glad that this guide helped you! Thanks so much for reading and letting us know. We appreciate the feedback!
I am looking for a pump for my floating ball fountain. The ball is 7″ in diameter and weighs 18 lb. Thanks in advance
I want to build a 30 foot (diameter) pond that is 2 feet deep at the bottom of a 200 foot wide lot. I want to pump the water from the pond to the top of the lot 200 feet away. There is 20 feet of fall from where I want the water to start back down the lot to the top of the pond (22 feet to the bottom of the pond if that matters). I want to create a “lazy river” effect that flows all summer. Any help would be awesome as to what pump/equipment I need to buy. Thank you!!
I use the Aquagarden 300 products in two of my ponds roughly the size of yours. They do a great job with the caveat that I substituted the polyester disposable pad with a fine reusable pad. The polyester provided was just not doing the job for fine particles. I clean the unit once every 7-10 days. I have four shubunkins in my pond. If the water is changed regularly they will easily grow to 12-14 inches, my breeding group in my bigger pond have reached this size, so keep an eye out, you may need to add a second filtration unit or perhaps go ahead and go up one size on your Aquagarden. In a year or two I will likely add a spitter with separate filtration to make up for the larger size of the fish if needed.
I have a 300 gallon water feature that is 1/2 pond and 1/2 pondless with a waterfall that is 3 feet above the surface. What size pump do I need?
I have a 80 ft by 50 by 8 ft deep pond. Aprox 220000 gal. I would have to run an insane amount of pumps to circulate this much water. What is minimal recommended for flow rate. I’m also putting in a 15 x 20 bog style upper pond as a natural filter with plants and barley and sand dam for filtration an algae control. I plan on adding trout
We have a pond we built that is rectangular. Length (10 feet), width (7 feet) and depth (2.5 feet).
Still confused what size pump and filter we Will need.
I have a 300 to 350 gallon pond ( best guess we timed filling a 5 gal bucket.. I have two pumps one is for a fountain .
The second water is going through a a large pond tetra pond skimmers
The hose to the pump then about 5 to 6 ft the water fall is about 18 to 24″ above the pond, the o
hose to a 8″ water fall. Is about 5 to 6 ft long. Right now its a very gentle flow. I’d like to get a med flow. What size pump should I get. Right now I believe its around 300 gph.