Hot Tub Pump Humming? Not Turning? You Need to Change the Startup Capacitor

If your Hot Tub Pump is humming and not turning. Or, if you have a "Heater Dry Error" on your control panel topside, there could be a problem with your Hot Tub Capacitors. In this video, we will take a look at the role of the Startup Capacitor and the Run Capacitor. We will look at how we can identory a bad capacitor. Then we will look at how we can replace the capacitor in the Hot Tub Pump.


This is a quick and easy job and the Hot Tub Capacitor is a consumable item. At some point, you are going to need to replace one in your pump. This video will show you how.


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What is a Capacitor?

A capacitor is a device that stores an electrical charge. The basic unit of capacitance is the Farad (F). One farad is a very large amount of capacitance and one micro farad (µF) is a very small amount of capacitance. Most capacitors are measured in µF or millionths of a farad.

How Does a Hot Tub Pump Capacitor Work?

We’ve already established that a capacitor is an electrical device used to store electrostatic energy a bit like a battery. It consists of two pieces of conductive material separated by a dielectric.

The nonconducting dielectric is designed to increase a capacitor’s charge capacity. Unlike resistors, capacitors do not dissipate energy and instead store it in the form of an electrostatic field. Think of them like a battery!

A displacement current can flow when an electric field develops across a capacitor and the potential difference across the conductors is large enough. For example, in our hot tub case when power is sent to the pump from the Spa Pack.

Different Capacitor Types in Hot Tub Pumps

A Hot Tub Pump essentially has two different types of capacitor. A Startup capacitor which tends to be the larger of the two and then a smaller run capacitor.

When a startup capacitor is charged, it provides power to the starter motor temporarily until the second phase winding spins up. Think of the capacitor as a battery just like the ones used to start your car. When the first phase winding of the motor spins up and is up to speed, it then passes over to the Run Capacitor and this capacitor stays in the circuit until you turn off your spa pump.

The start capacitor will generatlly be rated at 50-400 MFD and 125 or 250 VAC. The run capacitor will generally be rated at 15-50 MFD and 370 VAC.

Where do I find the Hot Tub Pump Capacitors?

Depending on the pump model that you have, they may be located in a different position to the example below. On a Waterway or LX pump, they are usually found on top of the pump in a sealed box like below.

On all pumps they will be underneath a cover so you need to locate something on the pump that looks like a removable cover and they will be underneath.

BE CAREFUL – make sure that you turn off the power. However, as we have learnt already, the capacitor is like a battery so treat is as if it is “live” and do not under any circumstances bridge the two connectors as you could get a strong electrical shock.