Your Spa Pump HP is a Lie

Why Your Spa Pump’s HP Is a Lie

A lie, I say!  Pump manufacturers may categorize it as a “fudging of the numbers” but let’s call a spade a spade. They are at best trying to mislead the homeowner. We take phone calls from customers every day attempting to match their current motor label information to a new replacement motor and a confused groan usually follows our explanation of the result.  Well, we finally had enough of the manufacturers’ trickery and we want to put you in the know. Time to break it down like a fraction.

My Kingdom for a 5 Horsepower

When you’re talking to a “car guy” about his vehicle, the audience can see him puff up his chest after he says some huge horsepower rating.  It is a source of pride for any man – and some women – who like to know they have the biggest, baddest thing on the block.  Well, manufacturers of spa pumps play on that machismo factor and use it while rating their pumps.

When a spa owner calls us with a 2 HP motor part number which cross references to a 1 HP replacement, it usually results in a protest of But I have a 2 horse power.”  Well, you do have a “2 horse power” but it is not what you think.

Waiting for That “SPL” Someone?

Before we get too in deep in the minutia of motors, let’s talk about the crux of the matter – the service factor. The motor has a listed HP but its actual total HP is calculated using the service factor as a multiplier. So that hulking 3 HP motor sitting on your pump could be a 2 HP paper tiger. The SPL under your motor’s service factor rating means that it is a special rating per the manufacturer’s request. Special is not always good.

For example:

Pool Pump 3 Horsepower X 1.25 Service Factor = 3.75 HP

 Spa Pump 3 Horsepower X “SPL” Service Factor = 2 HP or less

That “SPL” rating is a sign that the service factor is less than one which allows them to inflate the HP rating. This has the triple effect of boosting the rating, your pump’s ego, and its price tag.  Below is a chart taken from A.O. Smith-Century showing comparative SPL horsepower ratings to their flat service factor actual output.

As you can see the ratings on a motor are skewed by that one number called the service factor.

What is the Trick?

When faced with a spa pump owner convinced they have a 4 horsepower motor but the part number calls for a lower HP, we usually refer to the amps rating. When labeling a motor the maker can adjust the service factor but they cannot hide the electric usage of the motor. Whether the pump is normally rated or has the SPL stamp, the amp ratings of the two motors are virtually identical.

If you don’t know, now you know…

Well, now you know the deep, dark secret of spa pumps and it time for you spread the word.  We write this blog mainly for our own sanity during the pool season so we do not have to explain a hundred times a day.  But if you have more questions about spa pumps or anything pool/spa related, give us a call at 877-372-6038

18 thoughts on “Why Your Spa Pump’s HP Is a Lie

  1. HI,
    I hope all is well.
    Are you able to tell me how many hp is a 5SPL pump motor from Sunrise? Thanks!

    1. Just go by amps when comparing pumps. The Sunrise pump is 12 amps. V X A = P.
      Therefore, that pump is 2,760 watts. Or just under 4 HP assuming nominal voltage of 230.

  2. Matt, I have a one-person jacuzzi in my bathroom. I don’t know anything about it since it was in the house when I bought it. 3 large jets. I want to find a smart switch that will work with it. Any leads you can offer?

    1. I don’t have much info on smart switches or Jacuzzi bathtubs. My presumption would be first to figure out what type of equipment you have to then see what wiring is necessary. You’ll likely need to find the access panel to read the information tag and/or pump info

  3. I have a spa with a newer Balboa controller and 2 pumps listed as 5 hp that are working well. I have been given another tub that has a nicer shell and tub, but the controller is not as nice. Both the pumps are listed as 3 hp. I would like to take my controller and pumps and put them in the new tub. Any risk of too much water movement or pressure? Thanks!

  4. Matthew – I’m hoping you can help me. My old Flotec pool motor, model C48K2PA105 (pump model #AT251501-01) seized up and I had to replace. I’ve purchased and installed replacement motor U.S. Motors 1081 Pool Motor model K63CXEAP-5221. The old Flotec HP was listed at 1.5 SPL (which made me read your article about SPL). This new motor is intermittently not working (not filling, etc.) and acting like it is not drawing enough amps to kick on. Following are the details of the old and new motors and I wonder if they are like for like or if I need to take the new motor back?

    Old Flotec: 115/230V, 15.3/7.6A
    New US Motors: 230/115V, 7.7/15.4 SF AMPS.

    why would the old motor and new motor switch the power and is this relevant or are my old and new motor good replacements for one another?

    1. Carol, I have the exact same issues with the same exact pumps! I hope to see an answer to this question as I don’t believe the pump is pulling enough and feel the HP is not what is claimed,.

  5. I am thinking of purchasing a Dr Wellness Tranquility Spa. What if any is your acknowledgement of this spa? It states that it has two 6 hp motors, but after reading your article I see this is not true. I am starting to wonder if they are putting a lot of bells and whistles on their product to charge more.

    1. Overstating the horsepower of a pump is an industry-wide practice, so I wouldn’t glean too much from that. I am not familiar with that particular spa brand but take any sales brochure claims and salesman pitches should be taken with a grain of salt. Do research of reviews, spa forums, or even ask an unaffiliated repair company their thoughts about the brand. Hopefully, that extra info will help you decide if you are making the right choice.

  6. I have a new sl 40 strong spa which list a 2 speed 5 bhp. On high it seems to be more like 2.5 to 3.0 hp. It is a 56 frame on a 220 50 amp breaker. What pump would you suggest to get an actual hp of 5 or 6 hp?

    1. I don’t believe they make true 5 or 6 HP spa pump systems. First, it would cost a lot of money just to operate. Secondly, the amount of water flow it would put out would be unnecessarily high. Unless you are attempting to pressure wash your driveway, you do not need a 6 HP pump.

  7. Pump 1 surges between low and high speeds, and when this happens, the topside panel locks/freezes up. Here is a Youtube video of the spa doing this:

    I have to shut the spa down at the circuit breaker. I have treplaced the topside control panel and this has not fixed the problem. I have done a thorough cleanign with a “purge” like product, check the wiriing and some other things.

    Yesterday, it seemed to be working fine but when my wife an I got into the spa, it started doing it again. Then it started going from off,, low, then high speed. Then, pump 2 came on all by itslef. And some other strange things. Then, it worked properly.

    Very strange.

    Can you help?

    1. This is a reply I received from one of our distributor’s spa specialist:

      -My first thought is the pump motor itself. Sounds like it could be the centrifugal switch. That can cause that type of surging. And kill both the capacitor and motor itself in a hurry.

      Below are some of the things I’d try in the field if I came across this.
      -Remove filter and leave out for the duration of the diagnosis.
      -Make sure all unions are tight on pump, and make sure all valves open.
      -Make sure all jets are open.

      -Check compatibility between topside control and the board itself.
      -Check system number against the topside info on the underside and if not compatible, try one that is.

      -Check dip switch configurations.
      We must make sure its set up for the type of controller you are supposed to use.
      Sometimes this can happen if its set up for a mini oval instead of a VL, for instance.
      If all that checks out. address the following…

      Power is definitely in need of being checked.
      -Incoming voltage, does that surge? Or is it stable on a meter and within range.
      -If its stable, then move on to the next part. If not, stop, call electrician.

      -If its stable at incoming, then check at receptacle where pump plugs in, is that power stable, or is it fluctuating.
      -If it’s not stable, it’s probably the relay which would require a new main circuit board.
      -If the power at the receptacle is stable and within range let’s move on to next step.

      -Shut down system, unplug topside.
      -Turn breaker back on and run system without the topside plugged in.
      -Water temp must be below 100 for this to work. Low 90’s or below is best. (the board itself has inherent programming that in the event no topside is plugged in, will bring water to 100 degrees and maintain it) all on its own.
      -After turning on the breaker and energizing the system, wait about 5 min, (since no topside, cant bypass the PR cycle.)
      -After the 5 min, the pump one low should come on.
      -If still surging, I’d try another pump motor, or main circuit board.
      -A persistent memory reset of the main board, as a hail Mary play, may also be something to try.

      Good luck.

  8. Hi Matt,Great article.My spa motor just quit working and after reading your article it sounds like I could drop down in HP and save some money.I need the motor and wet end.Below are the specs off the GE Motir that is dead.Coukd you Mack a recommendation as to a replacement.Thanks for your time and opinion.
    V-230,RPM 3450/1725,A 12.0/3.9,HZ 60,PH 1,Code E,SF 1

    1. Simply multiply volts times high amps which in your case is 12.0. Once you have your answer, divide it by 745.7 for your horsepower. In your case your pumps horsepower is 3.7 hp. Mac’s Hot Tub Service.

      1. Don’t you also have to factor in the efficiency of the motor – your result of 3.7 hp assumes 100% efficiency, while even the best electric motors are only 90% or so efficient in converting amps to power. Multiply 3.7 x 0.9 and you get 3.33 hp which is probably closer to reality.

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