Pentair IntelliFlo 2 VST Variable Speed Pool Pump

Why “Oversize” A Variable Speed Pool Pump

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We have heard it over and over again. A client tells us that their pool builder or service company said a 3 horsepower Pentair Intelliflo pump is too big for their pool. It’s oversized. It’s overkill. It will destroy their pool plumbing. It will drain the oceans dry, trap baby seals, and eat all of the lobster in the sea.

Well, maybe not the last one…

We are big fans of big pumps. Why? Because they can run slow, quiet, and last a long time. That’s the whole idea of a variable speed pump. Really it’s a variable speed motor attached to a pump with a fixed impeller. You adjust the motor speed to change the flow rate. By “oversizing” the motor you can run it at a slower speed.

The result is super quiet and cool operation with long service life and a huge operating range to satisfy any flow rate for pool features and maintenance.

Example of Variable Speed Pump Options

Pentair IntelliFlo 2 VST Variable Speed Pool Pump

The Pentair IntelliFlo 2 VST 3HP Variable Speed Pool Pump is the Brand’s Flagship Model

Think of it this way. Pentair offers their flagship Intelliflo 2 VST variable speed pump that is rated at 3HP. They also offer a few other models of variable speed pump. Their lineup is:

  • Pentair Intelliflo 2 VST – 3HP
  • Pentair Intelliflo i2 – 2HP
  • Pentair Superflo VS – 1.5HP
  • Pentair Intelliflo i1 – 1HP

You might be surprised to find out that the i1 and i2 are the exact same motor and drive as the full Intelliflo 2 VST. They reduced the horsepower by just changing the pump impeller. The manufacturer did this to satisfy specific regulatory requirements regarding maximum flow rates in California and Arizona.

What is the result? You have to run the motor of these reduced horsepower pumps at a higher speed to achieve the same exact flow rate. That means more noise, more heat, and theoretically shorter service life. Even if you don’t think service life will be affected, noise is absolutely a factor. And guess what – these two pumps cost the same amount as the full Intelliflo 2 VST!

The Superflo VS 1.5 HP pump is a different motor and pump design. It does cost slightly less. But the result is that the pump motor must run at a much higher speed to achieve the same flow rate as the Intelliflo 2 VST. Again, more noise, more heat, reduced service life. While the pump does cost less, you have to buy a separate interface cable to connect it to automation systems, and it does not have the same automation options as the flagship Intelliflo series.

Common Sense

Why on earth would you install a reduced horsepower i1 pump when for the same price you can get an Intelliflo 2 VST with three times the horsepower? Just run the higher horsepower pump at a lower speed!

If you look at the performance curves for the two pumps, there is no question about the required motor speed to achieve a given flow rate.

Pentair Intelliflo 2 VST Performance Curve

Pentair Intelliflo 2 VST Performance Curve


Pentair Intelliflo i1 Performance Curve

Pentair Intelliflo i1 Performance Curve


For example, to achieve a 55 gallon per minute flow rate at 40 feet of head, the 3HP pump needs to run at 2,350 RPM. The 1HP pump needs to run at 2,700 RPM.

Now you may think that one of the two pumps will require more energy to run because of this phenomenon. However, in a pure physics sense, work is work. The same amount of work is being done (55 gallons per minute at 40 feet of head). The energy requirement differences will be negligible. The only time the 3HP pump will use more energy than the 1HP pump is when it is doing more work than the 1HP pump is even capable of doing.

My Pool Builder Disagrees

Stuck in the old days. Doesn’t understand physics. Focused on initial cost alone. Bamboozled by marketing.

We’re not sure exactly why your pool builder or pool service professional isn’t on board. We’re not even sure why one manufacturer even distributes the reduced horsepower variants in Florida. There may be a good explanation. We’re not pool professionals. But we are energy professionals, and we do understand pool flow and pressure dynamics. These are critical factors for solar pool heating.

The same thing applies to other manufacturers’ offerings. Hayward offers their Ecostar, Tristar VS, and Maxflo VS models. Jandy offers their ePump, VS FloPro, and VS PlusHP models. These pump series fit different price points for various pool designs. But the fact remains – for little to no extra money you can get a much more capable pump and run it at a slower speed.

The flagship “bigger” pumps also tend to have the most features, automation connectivity, and best warranties.

We do get one thing. Marketing drives sales. If you don’t truly need a 3HP pump, why buy a 3HP pump? Hopefully we have answered that here so you can have a discussion with your pool professional about what you want. We strongly suggest “oversizing” your variable speed pool pump to get the most out of your purchase.


  1. Hello, can I use this pump for my pond? Also, can you program this pump to run at a lower volume at night and a higher volume during the day automatically? I am currently running a Pentair 1and 1/2 horse power single speed motor which runs great but is costing me a bundle. Do I need any other accessories to go with this pump? Thanks for the info.

    1. Author

      I don’t see any reason you can’t use an Intelloflo pump for a pond. It sounds like a great idea. Yes, you can have up to 8 scheduled run scheduled, each with it’s own speed.

  2. Can I run a variable speed pump for a 25,000 gallon pool with solar heating and waterfall? How much HP needed?

    1. Author

      Absolutely, you can. However, without seeing your pool and existing plumbing we cannot make a determination as to horsepower. It’s not that simple. Usually a 3 HP Pentair Intelliflo pump is more than enough for residential pools. You will need to hire a local qualified pool contractor or solar contractor.

  3. Hi
    I have a 5,000 gal salt pool with a 1hp Pentair Intelliflow pump. For a 8 hour run is 1850 RPM’s enough ?
    2” PVC about 15’ away from the pool.

    1. Author

      Unfortunately, Frank, that’s not nearly enough information. You need a local pool professional to answer that for you after evaluating your system. The flow rate at any given RPM varies with both vacuum (suction) pressure and backpressure. The total dynamic head needs to be considered to determine the design flow rate at a given RPM. Or, get yourself a flow meter and see how much flow you have overall during your run time at your test RPM and ensure that you have the necessary turnover for your pool given where you live and the season. It’s quite a bit more complicated than a yes or no answer.

  4. For me, the biggest difference in choosing between these pumps is the power requirement. The 2hp i2 and below pumps can run on a 15amp circuit, while the 3hp VST pump requires a 30amp circuit. I’m needing to run 3 separate pumps (slide, waterfall, and pool/spa) so the cost of running a 90amp subpanel over 250ft from my main panel to my pool area is significantly more than running a subpanel to support 45amps.

    1. Author

      Hi James,

      Interesting point, but not correct. The Intelliflo VST requires 20A circuit protection. In the scenario you describe, it would require an increase in wire size by one AWG size in most scenarios. That should be a fairly low cost for a mountain of extra capability and lower noise. Other adjustment factors may apply for your feeder conductor. Consult a licensed electrician.

      It’s rarely an issue around here anyway since almost all pump circuits are 20A already, and for single pump scenarios, 5A difference usually doesn’t make a difference. Also, you might consider a larger pump and fewer pumps! Why run multiple pumps if you can handle features with valves and possible automation if necessary.


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