Dankoff Slowpump 2507-24 24VDC SURFACE PUMP

Dankoff Slowpump 2507-24 24VDC SURFACE PUMP
Dankoff Slowpump 2507-24 24VDC SURFACE PUMP
$760.05 List price $820.86
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Item code Brand name Model number
DAKSL-2507-24 Dankoff Solar Pumps Slowpump 2507-24

Dankoff SolarDankoff
MODELS: 1300,1400,2500,2600

Use Solar-Electric Power to provide 200-2,600 Gallons per Day (750-10,000 ltrs.) from shallow water sources. Slowpump can push water as high as 560 vertical feet (170m).

Dankoff SlowpumpSolar Slowpump was the world's first commercially available low power solar pump. It was developed by Windy Dankoff in 1983, in response to those who said "that's impossible." Thousands of Slowpumps have been installed worldwide by ranchers, homeowners, missionaries, health workers, government agencies, etc. Some of our oldest Slowpumps are still in daily service.

Slowpump is not submersible, but can draw water from shallow wells, springs, cisterns, tanks, ponds, rivers, and streams, and push it as high as 560 vertical feet and through miles (kilometers) of pipeline. Slow pumping minimizes the size and cost of the solar array, wire and piping.

Slowpump is less expensive than sub-mersible DC pumps, and made in a much wider range of sizes. Wearing parts typically last 5 to 10 years. Overall life expectancy is 15-20 years.

"The Slowpump #2507-24V is supplying water for a work camp on the outer island of Onotoa. It's supplying water for 60 people. The well is one half mile 800m away from the camp." -- B.C., Ministry of Works and Energy, Kiribati, South Pacific

"I have been very happy with the 1308 Solar Slowpump!...We are using it in a 5 meter deep hand dug well in a valley, and pumping 200 meters distant and 50 meters vertically." ---
Dr. D.L., World Missions, Cameroon, W. Africa

"These pumps work great.... Even during low light levels when the motor is turning slowly, a small amount of water can be pumped.... The manual is easy to read. Windy's troubleshooting section is excellent....Not only have these pumps stood the test of time, but small changes have made them even better." --- B. Schultze -product review in Home Power Magazine #42

Construction & Features

  • Rotary vane mechanism (positive displacement) made of forged brass, carbon-graphite and stainless steel
  • NSF® approved for drinking water
  • Handles sea water, dissolved minerals
  • Survives most freezes
  • Permanent magnet, DC motor
  • AC models use a low-surge PM motor that greatly reduces starting surges, inverter and wire size requirements
  • Installation and Service Manual is highly detailed and illustrated



Performance Charts

1300 & 2500 series 1/5 HP * PV Direct or Battery 12VDC, 24VDC, 48VDC, 115VAC
Model Numbers (Add -12 or -24 or -48 to indicate voltage)


Technical data Dankoff Solar Slowpump
Total Lift 1322 1308 1303 2507
Feet Meters GPM Watts GPM Watts GPM Watts GPM Watts
20 6 0.51 40 1.25 40 2.50 65 4.00 80
40 12 0.51 45 1.25 65 2.50 80 3.95 100
60 18 0.51 45 1.20 70 2.44 90 3.90 130
80 24 0.49 50 1.20 80 2.36 110 3.90 150
100 30 0.49 65 1.20 85 2.33 130 3.85 180
120 36 0.48 65 1.20 90 2.33 140 3.80 210
140 42 0.47 70 1.20 95 2.27 160 3.65 245
160 48 0.47 80 1.20 110 2.21 180    
180 54 0.47 85 1.18 120 2.11 190    
200 60 0.45 100 1.16 130 2.03 220    
240 72 0.44 120 1.14 150 1.96 235    
280 84 0.41 130 1.12 170        
320 96 0.41 150 1.10 195        
360 108 0.41 170 1.05 220        
400 120 0.40 190 1.00 250        
440 132 0.39 210            
480 146 0.25 260            
520 158 0.25 310            
560 170 0.20 340            

1400 & 2600 series 1/2 HP * PV Direct or Battery 24VDC, 48VDC, 115VAC
Model Numbers (Add -24 or -48 to indicate voltage)


Technical data Dankoff Solar Slowpump
Total Lift 1408 1403 2607
Feet Meters GPM Watts GPM Watts GPM Watts
160 48 1.82 185 3.43 280 5.93 430
180 54 1.81 200 3.40 300 5.83 470
200 60 1.81 210 3.35 330 5.80 500
240 72 1.77 235 3.38 360 5.75 585
280 84 1.79 260 3.30 405 5.59 675
320 96 1.72 290 3.30 450  
360 108 1.75 310 3.20 520
400 120 1.69 330 3.20 545
440 132 1.69 355 3.10 610
480 146 1.70 380
520 158 1.61 400
560 170 1.67 435


Reading the Performance Charts

  1. Identify Total Lift for your application = Vertical Distance from surface of the water source to the pipe outlet or top of storage tank, plus any pipe friction loss
  2. Choose SlowPump model based on desired output (GPM) and/or required solar power (PV Watts) at the Total Lift
  3. Select the desired pump Voltage from the available options for that model
  4. ** Actual performance may vary +/- 10% from specifications - based on PV-Direct voltage of 15, 30, or 60 (the standard Vmp of 12V, 24V, and 48V configurations at STC). For battery-based applications, subtract 20% from Flow and Watts.

    ** PV Watts column is the recommended power after taking the Watts required at the Pump and upsizing by 25% for de-ration, then rounding to the nearest increment of 5.

Suction Capacity

  • 20 vertical feet (6 m) at sea level -- subtract 1 ft. for every 1000 ft. altitude (1 m for every 1000 m). Pump should be mounted as close to the water source as possible to reduce suction lift.

Filtration Requirement

  • These pumps CANNOT tolerate dirt. Water MUST be filtered clear. Failure to use a Dankoff Solar Pumps filter unit, or use of a filtration unit other than Dankoff, will void the warranty on the pump. If water is very dirty, improve the source or consider using Dankoff's dirt-tolerant pump models (SolarForce, SunCentric, or Solaram).

PV-Direct (non-battery) Requirements

  • The rated power of the PV array must meet the Watts listed in PV Watts column in chart above.
  • A Linear Current Booster (controller) is required to function in varying light conditions (12V/24V: 5Amp, 8Amp, 15Amp, 48V: 10Amp)
  • Solar Tracker (optional) to increase daily yield (40-55% in summer)


  • Intake Strainer/Foot Valve with fine monel metal screen, stops course debris
  • Inline 10 micron Filter (10-inch) uses standard drinking water cartridges
  • Intake Filter/Foot Valve (30-inch) replaces Intake Strainer and Inline Filter (10 micron) with a single unit, best for lowering into a shallow well
  • Spare Filter Cartridges (5 or 10 micron spun fiber)
  • Dry Run Switch prevents battery drain and pump damage if water source
    runs dry
  • Linear Current Boosters (LCB) for PV-Direct (12V/24V: 5Amp, 8Amp, 15Amp, 48V: 10Amp)


  • 1300/1400 Series: 1/2 inch female pipe thread
  • 2500/2600 Series: 3/4 inch male thread


  • 1300/2500 Series: 5.75 x 17.4 inches (14.6 x 44.1 cm), 13 lbs (5.9kg)
  • 1400/2600 Series: 6.5 x 18.75 inches (16.51 x 47.63 cm), 25 lbs (1400 series), 29 lbs (2600 series)


  • 1 year against defects in materials and workmanship. Failure to use a Dankoff filter unit will void warranty.


Surface Pumps Comparison
Surface pumps for lifting and/or pressurizing water / 1 PSI = 2.307 ft. of
Surface Pumps Min Lift (ft) Max Lift (ft) Min Lift (PSI) Max Lift (PSI) Min GPM Max GPM Pump Type Dirt Tolerant Filtration Required Dry-run Tolerant
Solar Slowpumps 15xxx*
0 440 0 191 0.4 4 rotary vane N 10 mic N
Solar Slowpumps 14xx and 26xx
160 440 69 191 1 4 rotary vane N 10 mic N
Flowlight Booster Pumps 16xxx**
69 150 30 65 3 4 rotary vane N 10 mic N
SunCentric Pumps 7xxx
0 90 0 39 5 70 centrifugal high N Y
SolarForce PistonPumps 30xx
0 220 0 95 4 9 piston medium N Y
Solaram Pumps 8xxx
0 960 0 416 3 9 diaphragm medium N Y


*formerly 13xx and 25xx

**formerly 29xx


Dankoff Solar

Here are some tips from the altE staff

  • All Dankoff Slowpumps should have intake filtration. Filtration options are provided in the add-ons section. If the pump is located above the water to be pumped, a foot valve is required. Foot valve options are also located in the add-ons section. If the pump is below the water to be pumped, a check valve or foot valve is not required. A ball valve on the intake side of the pump is generally recommended in case pump service or replacement is required.
  • Do I really need a pump controller?
    • In the most basic sense, no. But for a variety of reasons, including the appropriate controller in your system makes for a better, longer lasting pumping system. A key feature to most pump controllers is what is called a linear current booster, or LCB. LCBs improve the performance of DC pumps by adjusting the voltage and current to increase the output in low light conditions, like mornings and evenings, and on cloudy days. But controllers do more than that. They reduce arcing between the brushes and the motor, significantly extending the life of the pump. Controllers also have terminals for a switch, like a float switch or pressure switch. Some controllers come with manual on/off switches, as well as internal fuses to protect against shorts. Finally, depending on the controller, they have low water probes, hi/low voltage protection, and other features. It is for all of these reasons that a pump controller is highly recommended.
  • Can I use a float switch without a pump control box?
    • Technically, yes. But because of the usual limitations, it isn't recommended. If one were to connect a float switch inline with the electrical circuit for the system, the wires in that switch would be carrying the current for the system. For systems with longer wire runs, comparatively larger wire is needed to reduce power losses. But the wire for a float switch isn't sized to carry large current loads. If one were to connect a float switch inline with the electrical circuit of a long cable run, the wires from the float switch would be insufficient handle the current and would result in significant power loss at best and melted cable insulation (and possibly a fire hazard) at worst. The contacts on the switch itself - what opens and closes the electrical circuit - would wear out sooner. Pump controllers typically have terminals for an electric switch (usually a float, pressure or dry run switch) that is a relay for the switch. As such, it makes it possible for the switch to function without carrying all the current in the system. This is why the wires for the switches are so small.
  • What if I just don't want, or can't, use a pump controller, but I want to use a float switch?
    • In this case you would have two options. First, if you can reduce the length of the float switch cable to a couple of feet, then probably the loss in the line wouldn't be too significant. But this will vary from one system to the next, and consulting a sales tech is recommended. The second option you have is to use a high current float switch. We have one that is designed for up to 25 amps. However, it contains mercury and is not recommended for drinking water.
  • If I want to make the wire longer on my float switch, can I do that?
    • Yes, if you are using a control box. The length will vary from one switch to the next, but for many switches you can extend the length up to 1000 feet and for some up to 2000 feet. On the other hand, lengthy runs usually means digging a trench to protect the cable from critters and exposure to weather. To avoid that challenge, one alternative is to use a combination pressure switch and float valve. When connected to a pump controller, a pressure switch will turn a pump on and off based on the pressure it senses in the water line. When the pressure rises, the switch turns the pump off, and when the pressure drops, the switch turns the pump on. A float valve (aka ball valve) is used when one is filling a water tank and will open and close the water line based on the water level of the tank.

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I will never buy another Dankoff


I purchased this pump to pump water from a shallow well up a hill on our farm. From the first time I turned it on it had lots of cavitation noise. After reworking the plumbing multiple times, I still didnt get it to run smoothly and within a day the pump head broke a pin on the inside of the hea...
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