What Size Pump Do I Need For My Water Feature?

What Size Pump Do I Need For My Water Feature?

Water features come in all shapes and sizes, and we get quite a few calls asking for outdoor water fountain pump recommendations. I used to sell concrete fountains years ago, and have some idea of sizes that are needed, but it really is hard to be exact. We make the best recommendations we can.

Getting to Know Fountain Head

The first thing a customer needs to know about a fountain or pond pump is "head." Head means the maximum vertical lift from the surface of the water to its outlet that a pump can push the water. Or, in the case of an MDM Sequence pump, the water is actually pulled. If your pump has a maximum head vertical height of six feet, it will only pump up to six feet high, and at that height there will only be a dribble.

In most pump manufacturer's specs, you will find maximum lift or HEAD, along with a Pump Curve. For example, the Fountain Tech 650 has a maximum of 140" in head height. At zero feet it pumps 780 gallons per hour, at 20" of head it is pumping 680, at 60" it is pumping 580. This "curve" in the table below shows how many gallons per hour the pump is pumping at different water lifts.

So if your water feature's outlet is three feet above the water's surface, you need to see an approximate measure of flow at 36".

What Amount of Water Does My Fountain Need?

Of course, that doesn't answer the question of how many gallons per hour you need to make your water feature look best. Too much flow can cause a great deal of splash, and then the fountain basin loses water too quickly and can run dry and burn out your water feature pump. Too little flow and the water will dribble and not move evenly from your feature.

If you have one of those fancy brass fountains shaped into dolphins or birds, you will need to have an idea of how much you want the water to "squirt" from the mouth or the fountain spout. The same goes for pond spitters.

The Classic Italian is perhaps the most popular style and can be two-tier to four-tier, typically. The bottom basin is largest and the basins get smaller until the final top, out of which the water flows. They also have, in the best and most expensive versions, a large circular pool at the very bottom.

As a rule of thumb, these fountains work best when enough but not too much water flows down the bowls. You want to have enough water so that the water flows down evenly, but not so much that there is a great deal of splash. When the water is rising about thirty inches or so, I have usually found a pump in the 140-170 gallon per hour range works right.

How to Choose a Pump

But the very best solution to determine the size needed is to know sizing dimensions from your previous pump. If you can still read the label, then that is probably the size you need, though it is hard to say for sure. This is for two reasons.

For one, different manufacturers rate their pumps' flow rates differently. Fountain Tech pumps usually are rated on the conservative side. For another thing, some manufacturers misjudge the best pump for their fountain, often including a larger pump than is optimal.

A lot depends on the kind of sound the customer wants their fountain to make, as well as the purpose of the fountain. Does the customer want a roaring sound or a tinkle? Both effects can be pleasurable.

Understanding the Pump Label

The label of the pump, if it is still there and has not been worn away by water, will give you plenty of information.

It should tell you the wattage or amperage, the voltage, and gallons per hour. Some pumps list liters per hour instead of GPH. A gallon is 3.8 liters. A Fountain Tech 300 gallon per hour pump is lifting over 1100 liters per hour.

Most small pumps include watts, not amperage. Think of a pump that uses 100 watts the way you would a 100-watt bulb. But if you must know the formula to figure out amperage, here is the water feature pump size calculator for calculating amperage use.

Watts ÷ Volts= Amps

Thus, the 70 watts pump above divided by 120 volts (standard US outlet) = .58 amps. So the FT-650 is using .58 amps (slightly over ½ amp).

Tubing Size

It’s best to use the widest diameter tubing you can. For instance, the Fountain Tech 300 pumps about 240 gallons per hour at three feet when using ¾" TUBING, but only 75 gallons per hour at three feet if you use ¼" tubing. Most pumps come with different adapters to fit different sizes of tubing.

Also, just so you know, it is often possible to insert snugly one size of tubing into another, for example, 3/8" tubing will often fit snugly into ½" tubing, depending on the thickness of the tubing walls. Your fountain may also use PVC pipe. Quite a few pumps offer female threads for inserting PVC male pipe, but make sure not to over-tighten the pipe into the pump, as the pump body could crack or you might run the risk of jamming into the impeller body.

Does Your Pump’s Size Fit?

Water feature pump sizing starts with determining if the pump you buy will fit dimensionally into your fountain's basin. Many fountains have cutout areas in which a pump is placed. If your pump is too large, obviously it won't fit.

Adjusting Flow

Most magnetic pumps have adjustable flow, but how much flow is adjusted depends on the way it is adjusted. Some adjust the water going into the pump; some adjust the water going out. Fountain Tech pumps adjust the water going in and the flow can not be adjusted by much.

How to Quiet Loud Pumps

Sometimes pumps can be too loud and interfere with the pleasant sound of the fountain.They may arrive loud, which usually means the impeller got jammed up during shipping.

Typically, the impeller (the propeller looking thing inside a pump) is housed inside a pump front cover. You snap off the pump cover gently, though you might need a flathead screwdriver, and find inside it the impeller. Larger pumps often have screws inside the cover, and once unscrewed, typically the internal plate needs to be turned counter-clockwise to release the internal plate.

If it's not the impeller, you can usually quiet the pump by placing cushioning beneath it, a sponge, for instance. Noise is caused by vibration within the feature's basin. Copper can be tricky.

Sizing a Fountain Pump Based on Purpose

Pot Fountains

For water to flow down all the sides of the pot smoothly and cover the entire pot, typically a large pump is needed. But you will need to get a recommendation from your manufacturer. We sell quite a few pumps to pot fountain companies, and they usually order either an FT-450 or FT-650 pump.

When Building a Waterfall

The general rule of thumb is to have 100 gallons per hour for every inch of width of the fall. So if your waterfall is 5 inches wide and 3 feet tall, you need to be pumping 500 gallons per hour at 3 feet of head.

But this rule can vary. A lot depends on the surface and level of the spillway. Jagged rocks require quite a bit of water to cover the entire spillway. Smooth acrylic or stainless steel surfaces require less.

Aerating a Pond

For small backyard ponds with fish, it is typically recommended that you recirculate the pond volume once per hour. So a 1,200 gallon pond will need to have a pump pushing the water about 1,200 gallons per hour out of the feature, whether it be a waterfall or fountain or combination of spitters.

For large ponds and lakes, like an eighth of an acre and larger, you don't need to recirculate the water every hour. But how much water should be pumped varies by manufacturer. When using a decorative fountain with an intricate nozzle, Kasco Marine recommends using a 1HP pump for every ½ acre of surface area (a 100 x 200' pond approximately). It should be noted that Kasco biologists and engineers make recommendations according to optimal pond health, and sometimes less HP works well enough.

Also note that this ratio is for Kasco fountains. Some companies provide very tall or very wide displays, but to get that water so high the nozzles are restricting quite a bit of flow. If you see a one-half horsepower unit pushing the water 40 feet into the air it is doing so by restricting the outflow of the pump, decreasing the aerating properties.

Kasco aerating fountains provide only one kind of display, the V-pattern. It’s not so much a nozzle at the top, usually, but an open vent. The flow is not restricted by an intricate nozzle and the pump uses a propeller rather than an impeller. Kasco recommends 1 ½ HP of fountain for every surface acre of water (a 200’ x 220’ pond).

Surface Aerators without display use a propeller without a nozzle of any kind. Kasco recommends a 1HP to 1 acre ratio (that is, 1 HP for every 200 x 220' of pond). Of course, this varies with manufacturer and shape of pond. To calculate the total surface area, gallons, or acre feet of your pond you can see our pond size calculator.

Whether you’re searching for a waterfall pump or a pump for your electric water feature with LED lighting, Fountain Mountain can assist. Be sure to contact us for assistance.

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