The Ultimate Guide to Hot Tub Pump Capacitors

Hot Tub Pump Capacitors

This guide discusses the two kinds of hot tub pump capacitors that are used on Hot Tub motors: start capacitors and run capacitors. It also addresses how to know when a capacitor is failing and how to replace it.

They are an inexpensive part of your Hot Tub pump and they are also certainly something that you are going to need to replace at some point. They do fail and they are a consumable part. Later in this article we will also look at how to replace them.

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.

Hot Tub Pump Capacitor

When do I need to Change a Hot Tub Pump Capacitor?

As I have mentioned already, at some point, you are going to need to change the capacitors. They do wear out over time.

There are a couple of ways to identify if your capacitors are on their way out or have failed, when you press jets on your control pad, you will hear the relay click, and your pump will “hum” but it will not turn.

To clarify this, if you press jets again and the high speed kicks in, then it is definitely the startup capacitor that has failed. Press the jets again and the pump will run in low speed after it has been on high speed. It will just not start – this is the startup capacitor failed.

Visually, you can see if the capacitor has swollen or become misshapen, then this is the sign of a bad capacitor.

If the run capacitor has failed, the pump will be noisy and sound really lumpy when it is on high speed.

If you would like to measure the capacitance on your multimeter as a check, the capacitance reading would be significantly lower than rated if it’s failed or on its way out.

How do I Measure Capacitance with a Multimeter?

Using a multimeter, check to see if the capacitor is bad. Place the meter’s leads on either terminal of the capacitor. You are going to want to set your meter to the lowest ohms setting available to you.

If the reading remains at 0, then it’s time to replace that component and test again with a new part. You should be able to get a higher reading on the new capacitor that you are about to replace.

How do I replace a Hot Tub Pump Capacitor?

Firstly, you need to located the cover and remove it. As we have said, every pump is different but you are looking for a cover that could house the capacitor. It will be accessible and usually is on the top.

If the capacitor is mounted on top of a bracket which holds it in place, then unscrew this from the pump.

Then you can just remove the old capacitor by pulling it out and catch the leads so they don’t fall inside the pump. You may need to unscrew the capacitor from the terminals of the pump.

Once you have removed the old capacitor, simply do all in reverse to install your new one.

You need to be careful not to touch the two wires to each other as you pull the capacitor out. They will be connected together inside the pump and touching them can cause a short circuit causing damage to your wiring or worse, electric shock.

Replacing the capacitors will save you having to replace the whole pump. It is totally something a DIYer can do and is a 15 minute job.

Hopefully this article has been helpful in providing information on how to identify, test and replace a capacitor that might have gone bad.

Thanks for reading

Happy Hot Tubbin’

Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi


Hi, Andi here. I own and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Today, I've helped over 1000 DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi

Soaking in Success: What Makes the Best DIY Hot Tub Plans?

It’s that time of year again where the second wave of DIY Hot Tubs and [...]

Paul’s DIY Hot Tub Journey

Paul decided to take the plunge (pun intended!) and build his own hot tub, and [...]

DIY Hot Tub / Swim Spa Case Study – Darren, AZ, USA

Darren got in touch with me April 2024 because like most of my customers, he [...]

How Noisy is an Air Source Heat Pump?

In my latest video, which you can find below, I take a look at how [...]

Installing a Main Drain for Your Hot Tub or Plunge Pool

Installing the main drains that you are going to need on your hot tub or [...]

Rebar for Hot Tubs and Pool Construction Explained

Imagine soaking in a steaming hot tub or cooling off in a refreshing pool on [...]

Infinity Hot Tub with Swim Jet Takes Shape in Virginia

Have you ever dreamt of soaking in a luxurious hot tub while enjoying a mesmerizing [...]

Keeping Your Pool Crystal Clear: A Deep Dive into Sand Filters

Sparkling pool water is every pool owner's dream. But achieving this oasis of refreshment requires [...]