How to Choose the Right Pond Pump

What Does a Pond Pump Do?

    Pond Pumps perform several valuable functions:
  • Water Movement: The pump is the Quarterback of your pond equipment team. It gets the water to its goal.
  • The players guarding the Pump are the Pond Filter or a pre-filter that is attached to the pump's intake. It is the job of the guards to keep debris and particulates away from the pump so that it does not get clogged and lower the water pressure.
  • The pump circulates the water through other pond features such as the filter, a skimmer, a waterfall, or a fountain. Those pieces of equipment are the defensive team. They try to stop the quarterback from getting to the goal

How Much Work Can YOUR Pump Do?

    How much work your pump needs to do depends on several factors:
  • Rule of thumb is that the pump should be able to circulate 1/2 the volume of the pond each hour. If you only need to circulate water through a filter and back to the pond, use the recommendations for the particular filter you are using to decide how large the pump should be according to how many gallons your pond contains.
  • How many gallons of water DOES the pond contain? Obviously, if it is a large pond, the pump will need to pump more gallons per hour than if it were a small pond. See how to calculate the size of your pond
  • Will Your Pump Power More Than Just a Filter? Because each Waterscape is different, it is hard to include a pump of the appropriate size with any one piece of equipment. The recommended pump for a certain filter is not large enough to power that filter PLUS a waterfall. The recommended pump for a pond skimmer is not large enough to push water to a filter, a waterfall AND power a fountain too.

    Think of each piece of additional equipment as a stop light on a freeway. An unencumbered pump bringing water in one side and out the other will give you its maximum speed like a race car driving in Wyoming. Add a Fountain, and it will slow it down: lowering the amount of gph it can reach. Add a waterfall and it will slow it down further.

  • Will it Need to Push Water Uphill? Fountains go high into the air. Waterfalls "FALL" down into the pond from an uphill mount. It takes more pressure to push the water to those heights.

    Head is the amount of "push back" your pump receives on its way to its destination. That can come from gravity pushing the water down while the pump pushes it up. It can come from resistance in long tubing. It can come from elbows in plumbing. Anything that works against the pump is considered a measurement of "head"

    Head "Height" is the distance above the pump that water must rise to satisfy the added piece of equipment. How high above the pump is the waterfall? How high above the pump is the fountain expected to rise? As the need for water above the pump increases, the power of the pump to push water that high diminishes.

    ie: a pump that can push 500 gph with no uphill climb can only push 180 gph at 6 ft head height (if water must rise by 6 ft).

    Anything that impedes the progress of the water will require more power from your pump. Adding all of the "stop lights" will tell you how much more power you need than the equipment calls for in its natural state.

  • Order a larger pump that recommended by any one piece of equipment if you will be attaching them in-line to each other.

Fountain?

    Fountains add interest, sound, and aeration to your pond. They enhance its beauty and also help to discourage mosquitoes from breeding on the water surface.
  • Some pumps come with fountain attachments. Water comes into the pump at its inlet and shoots out the top in a fountain back into the pond.

    Aeration is the process of adding oxygen to water. Maintaining healthy levels of dissolved oxygen (DO), one of the most, if not the most important water quality parameters, aids in the breakdown of decaying vegetation and other sources of nutrients that enter your pond.

    The decomposition requires a continuous supply of oxygen and proceeds more rapidly as dissolved oxygen concentrations near saturation levels. The sulfury pond muck smell can be caused by too little oxygen feeding the beneficial bacteria that aid decomposition. The more decomposition we can facilitate, through the addition of oxygen with aeration, the less nutrients there will be available for algae blooms and excess aquatic plant growth. Read more about Biological Filtration Here

    A fountain is your best friend.

  • Small fountain pumps ARE the filter. They contain a pre-filter sleeve on the intake to protect the pump from debris. They suck water in and expel it through the fountain attachment.

    Larger fountain pumps suck water through a separate filter and expel it through a fountain back into the pond. (The better option for all but the tiniest of ponds)

  • Remember that a fountain adds drag to the water and slows the pump, which is trying to push it up-hill. Figure your pump flow needs by the formulas above according to the height of the fountain top above the top of the pump (Head Height).

    ie: a pump that can push 500 gph with no fountain can only push 180 gph at 6 ft head height (if water must rise by 6 ft). Get a bigger pump if you need 500 gph WITH the fountain included.

Skimmer?

    Skimmers sit in the pond with their opening just at the water line slurping the debris off of the surface before it falls to the bottom and decays into toxic pollutants. They can save you hours of pond cleaning.
  • Each skimmer has manufacturer's recommendations for the size pump that is needed to pull the water into the belly of the skimmer where it is trapped.

    The recommendations usually involve how large the pond is in gallons, and you can use those recommendations if the skimmer is the filter too and the sum total of features you are using.

  • If the skimmer contains the pump for the whole pond, and you have other features such as a separate filter, a fountain or a waterfall, you must add the recommended gph for the skimmer pump with the needed head requirements for your tubing, fittings, height above the skimmer for a waterfall or fountain etc. according to the calculations above.

Waterfall? How Big Should the Pump Be?

    Waterfalls add visual and aural appeal to your backyard.
  • Most people think of a waterfall as an add-on to a pond. However, they are also wonderful when used as the ONLY feature in your backyard - and easier to care for.
  • Some General Rules for Waterfalls: A 1/2” deep water flow at the weir (the spillway edge) requires 100 gallons per hour (gph) per inch of width. Most residential disappearing waterfalls are twice that.

    To determine pump flow at the falls: Head pressure may be calculated using 1 foot of pressure for each foot of height above water level and 1 foot of pressure for each 10 feet of tubing after the €first 10 feet. Add another 1 foot of head for every elbow or T fitting in the plumbing

    Example of Head Pressure Needed with 24" Spillway:

    • Your waterfall is 24" wide at the spillway and requires min 3600 gph pump. It is 4' above the ground level and 10' of tubing with 2 elbows.
      4'high + 1' for tubing + 2' for fittings = 7' of head.
      You will need a pump that provides 3600 gph at 7' of head to achieve the desired effect for the waterfall or stream.

  • Flow over the spillway: The more water that flows over the spillway, the louder the sound will be. Width of the Spillway x Desired Flow = Total GPH

    Light Flow: 100 gph per inch of spillway width

    Medium Flow: 150 gph per inch of spillway width

    High Flow: 200 gph per inch of spillway width

    Example Flow Rate with 24" Spillway:

    • Light Flow: 24" spillway x 100 gph = 2,400 gph
    • Medium Flow: 24" spillway x 150 gph = 3,600 gph
    • High Flow: 24" spillway x 200 gph = 4,800 gph
  • Sizing Your Stream and/or Reservoir (#8 in the image above) for a "Waterfall-only" Feature: If you only have a waterfall, the size of the Reservoir IS the "pond". The pump will be sized to accommodate your reservoir volume (instead of pond volume) plus all of the head and flow calculations you need.
  • Make the reservoir 3 time the volume of the total water in the stream or waterfall. Width of the Stream x Length of the stream x the Average depth of the Stream x 7.5 gallons = Total gallons in the reservoir.

    Example Reservoir:

    • Stream 3'W x 20'L x .25" deep x 7.5 = 112.5 Gal
    • Multiply 112.5 gallons x 3 to get the Reservoir Gallons = 337.5 gall of water.

The Difference Between Submersed, In-Line and External Pumps

    Submersed:
  • Any submersible pump can be laid or mounted under the surface of the water where it is not visible. It pulls water through the filter (whether also submerged or on the land at the water's edge), which expels clean water back to the pond.

    They can also sit in the belly of the Filter, Skimmer, or Waterfall.There they draw water into the equipment chambers and push water back to the pond.

    In-line:
  • In-Line pumps Can be either submerged or mounted outside the pond. They are not contained inside the equipment but attached to other features in series. ie:: filter to pump to UV clarifier to waterfall. All or most of the components are external to the filter (not contained inside the filter).
    External:
  • External pumps are not submersible at all. They must remain on dry land. The pump (either contained inside the filter, submersed in the pond, or mounted in-line on land) draws water from the pond up into the filter on land. The filter sends it back to the pond cleaned.

Will it Need to Fit in a Small Space?

    There are some simple filter/pump combination kits.
  • However, most filters come without a pump. Most Skimmers, Fountains, and Waterfalls also lack a pump. It is important to know where the pump will be located.
  • Most equipment is in-line - attaching the equipment in sequence: ie:: filter to pump to UV clarifier to waterfall. All or most of the components are external to the filter (not contained inside the filter).
  • Some equipment is built to house the submersed pump inside the belly of the feature: The pump fits inside the skimmer to the right. Some pumps fit inside fountains.

Considerations for Your UV Clarifier

    The water that passes over and around your UV bulb must not move too fast.
  • You would think that the more powerful the pump is the better. While it is true that a little larger than necessary is better than smaller than needed is a good rule of thumb in case your fish grow or you want to add water features at a later date, a pump pushing water too fast over the UV bulb will not give the algae cells and pathogens enough time to be killed by the light. The must have an adequate "dwell time" (the length of time they are in contact with the ultraviolet light)

    So curb your desire to have a super-pump in favor of one just slightly larger than your current needs and not too powerful for the manufacturer's recommended pump flow for the UV light.

How Much Do You Want to Spend?

    How much money do you want to spend? The best pumps will give you plenty of power to run add-on water features and still draw water through the filter at an adequate speed. Generally, larger pumps cost more.
  • How much time do you want to spend maintaining your pump The best pumps filters will have easy-to-reach maintenance areas, few moving parts, maybe protective pre-filters or other features that make maintenance easier. More features, more money.
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