Skip to content
Get Quick Online Water Pump Sizing Now »
Get Quick Online Water Pump Sizing Now »
Pump Detective: Whats the Horsepower of My Pump? 5 Easy Ways to Figure it Out!

Pump Detective: Whats the Horsepower of My Pump? 5 Easy Ways to Figure it Out!

We're going to cover how to find your water pump horsepower, model numbers, voltage and amp ratings. If you hit a dead-end and need some help, call our pump technicians at 855-560-5670 and we'll get you on the right track! 

1. Check the markings on the pump motor 

Both above-ground pumps and submersible pumps typically feature visible labels indicating horsepower, motor amps, and voltage. Sometimes this information is laser engraved on the pump, so take a second glance in some good lighting if you don't immediately see a printed label. 

submersible 4" water pump, pump end, well pump label

However, retrieving such information for submersible pumps buried deep underground can be a challenge if you haven't pulled the pump out of the well yet. Another option would be to check the control box...

2. Check the labeling on the control box

Submersible pumps are equipped with a control box where the well pump wires connect and the wires to the breaker box also route in. The exterior of the control box is usually grey in color and displays a label. This label may tell you a few things, like the model of the control box itself, and the brand of the control box. Sometimes control boxes are made to match with one specific horsepower of pump, like a 1HP, or a range of power, like 1/2HP up to 1 HP. Google the model number and take a look at what the manufacturer specs are. Some manufacturers may provide additional details inside the control box. Accessing the internal labeling may require removing the control box cover using a screwdriver. Remember to turn off the power before handling electrical covers and adhere to safety precautions.

3. Call the contractor / well driller who installed the original pump

If there are no visible labels to help determine your horse power, there are a couple other options to figuring out your pump specs. Consider reaching out to the contractor or well driller who originally installed the submersible well pump as they often retain invoices containing essential details such as horsepower, wire and pipe size, and installation depth. Sometimes the contact information of the well company is on a sticker or plate on top of the well, or nearby the control box. Other times you may have been given the paperwork as part of the purchase of your property.   

If all else fails, you can also ask the company to come out of inspect the pump for you or take some electrical readings, which we'll cover in the next section. 

4. Find you well log

We have a full blog on  How to find your well log. This might help you figure out your well depth, static water level and recovery rate of your well. This info could be used to determine your total head which will come in handy later.

5. Take some well pump readings with a multimeter 

 If you cant get to any of the labels on the pump or control box, but don't want to hire a professional quite yet AND you have a multimeter handy try this next step.

You'll need a clamp or probe multimeter like this one...

Option #1 Measuring Amps with a Clamp Multimeter 

You're going to need access to the wiring the goes from the pump control box to your breaker. Typically, this wire is bundled and hard to access, but if you open up the control box of the pump, you'll find the L1 and L2 wires available. Chose either of the L1 or L2 to measure. Place the clamp over the wire, set the clamp multimeter to AC amps. Test while the pump is running. Record the amp number. 

Based on what amperage you record, this can give us a ballpark idea of the horsepower of your pump.

Option #2  Measuring Resistance with a Probe Multimeter 

Disconnect the breaker.

Open your pump starter box. 

Pull off your red, yellow and black wires from the starter box. These are your pump wires. Some people have different colored wires, like a white wrapped wire instead of yellow, it's a direct substitute. Do not remove the ground. Now you have access to the bare copper of the wires. 

Grab your multimeter, set to Ohms (the upside down horseshoe symbol) to test resistance.

You'll test two wires at the same time,

1) black to yellow (running winding) 

2) red to yellow (starter winding)

Black to Red is the sum of the readings from 1 + 2. 

With each hand, hold a metal probe tip to a bare wire. For example, black probe tip to black wire end, red probe tip to yellow wire end.   

Record your numbers. With those readings we can reference the below chart to figure out the ranges your readings fall into. Take note that the further away you measure the resistance from the pump, your numbers will slightly change.

Option #3 Using Circuit Breaker Amps Ratings  

Take a look at your electrical breaker box, the larger HP of motor your pump is, the higher circuit breaker amp rating required. Reference the below chart. 

Motor HP Full Load Watts   Full Load Amps Maximum Load Watts Maximum Load Amps  Circuit Breaker Amps
0.5 HP ~670 ~5 ~ 15
0.75 HP ~940 ~6.8 ~ 20
1 HP ~1210 ~8.2 ~ 25
1.5 HP ~1620 ~10 ~ 30
2 HP ~2025 ~10 ~ 30
3 HP ~3000 ~14 ~ 40
5 HP ~4830 ~23 ~ 60
Previous article How do I calculate what size pump I need?