The Ultimate Guide to All Things Hot Tub Pump

It’s amazing how little consideration you probably give your Hot Tub pump when it’s working properly. Arguably, it’s the most critical part of your Hot Tub. Without it, you basically just have a really large bath in your backyard! As it operates, it circulates the water throughout your tub—first through the filter to clean it, then through the heater to warm it, and finally, back into the Tub through your jets as the pressure builds.

But what if you turn the Hot Tub on and hear a loud, screeching sound? Or your jets kick in, but barely any water is flowing through them? Or even worse—nothing happens at all, and the pump is just humming. Anyone up for a cold tub? Didn’t think so!

It is important to recognize the signs of pump trouble. Even more important is understanding what steps to take to prevent problems before they occur—and what to do when they inevitably do.

What’s in a Hot Tub Pump?

Before attempting to repair or replace a malfunctioning pump, it’s important to familiarize yourself with the specifications of your Hot Tub pump. Most pumps have key specs listed on them, such as horsepower (HP) and speeds. You may also come across other specifications like discharge, inlet size, and maximum head height, but the most important factor is typically the horsepower.

Variable or Single Speed

Every Hot Tub needs a pump that can both control the jets and circulate the water. This means you require both high and low speeds, which are measured in revolutions per minute (RPM). When a single pump can switch between high and low speeds, it’s referred to as a variable-speed or two-speed pump.

Some Hot Tubs instead have single-speed pumps but compensate by using two separate pumps. In this setup, one pump—called the circulation pump—requires less energy than most other pumps and operates at a much lower speed. Circulation pumps typically move between 25–35 gallons per minute (GPM) and have a lower horsepower, usually ranging from 0.3–0.5 HP.

Even small variable-speed pumps can push 100 GPM or more, while the most powerful ones can reach up to 260 GPM.

If you have a two-pump setup, the second pump operates at a higher RPM to control the jets in your Tub. To sum it up: your Hot Tub needs both continuous water circulation and a higher-speed pump (or mode) for the jets to function properly.

Wet and Dry Ends

It could completely destroy the pump if water ever reaches the motor portion of your Hot Tub pump. Unfortunately, I know this all too well from first-hand experience. Let’s just say, submerging your pump in water is a terrible idea. Once it rusts, you’ll have no choice but to replace it—just like I had to.

Every pump has a “wet end” and a “dry end” to keep it working by separating the electronic parts from the water.

The wet end houses the impeller, which pushes water into your Hot Tub circulation system. The dry end contains the “engine” and is enclosed in a sealed housing to protect it from moisture. Both ends have components that can fail and cause problems with the pump.

For instance, if your impeller gets clogged with residue, debris, or hair, you’ll start noticing flow issues. And if the motor wiring shorts (which is exactly what happened to mine!), it may randomly trip your breaker.

It is possible to fix each end separately when only one part malfunctions. However, in most cases, replacing the entire pump is more cost-effective and saves you both time and frustration!

Voltage

To operate, the “engine” in your Hot Tub pump requires the right electrical supply. It’s crucial to know whether you need 110-120V or 220-240V.

• If your pump has two wires powering it, it runs on 110-120V. Typically, these wires are green and white.
• If your pump has four wires, it requires 220-240V. In the U.S., these wires will usually be gray, white, red, and black—but European color codes may differ.

The correct voltage for your pump should be listed on the unit’s specifications. What you don’t want is to underpower your pump, as this can cause damage. For example, if you don’t step up a U.S. 110V supply, you won’t be able to run a 220V pump! Most Hot Tub components are 240V, so always double-check your specs.

Horsepower

The horsepower (HP) in your Hot Tub pump determines its power output—just like the horsepower in a car engine. Hot Tub pumps range anywhere from 0.3 HP to 5 HP (and sometimes more!).

However, you can’t just install a 5 HP pump in any Hot Tub and expect it to work perfectly. The plumbing must be able to handle the increased pressure, or you risk restricting water flow—or worse, causing leaks.

One thing to keep in mind: Some pumps are slightly over-rated by manufacturers. The power listed on the specifications is often the peak output tested in a controlled setting—not what the pump will actually produce in your backyard. So, you do have some leeway when selecting your pump.

Discharge

The discharge orientation refers to where water exits the pump. It will either be:

• Centered
• On top
• On the side

Since all pumps look similar, you’ll need to check the specifications to determine the discharge position. However, you can trace the plumbing by following the pipes that connect to the drains and skimmer—this will help you identify the inlet.

Tip: Some pump manufacturers use non-standard fittings. If this is the case with your new pump, you’ll need to replace the joints during installation. You may also need plumbing reducers or converters to properly connect the pump to your pipes.

Frame Size

Your Hot Tub pump is secured inside the tub using pre-drilled holes in its housing. These holes must align perfectlywith the mounting points inside your tub—otherwise, you won’t be able to install the pump correctly.

Hot Tub pumps come in two standard frame sizes: 48 and 56.

• If your pump has a label, you should see either “48” or “56” printed on it.
• If there’s no label, you can measure the distance between the mounting bolts:
  • Less than 4 inches apart? It’s a 48-frame pump.
  • More than 4 inches apart? It’s a 56-frame pump.

Tip: Always double-check your pump’s frame size before ordering a replacement—choosing the wrong size could make installation impossible!

How to Prime Your Hot Tub Pump

When you fill an empty Hot Tub, air can get trapped in the circulation system, preventing proper water flow. Priming the pump removes this air, ensuring smooth operation.

Even self-priming pumps may need assistance from time to time. Since priming methods vary by model, check your manual for specific instructions. That said, there are two simple priming techniques you can try.

Control Panel Priming

If your Hot Tub has a priming mode, you can clear the air with just a few button presses.

1. Locate the priming mode in your control panel (if available).
2. Turn your jets off for 10-20 seconds.
3. Turn your jets on full for another 10-20 seconds.
4. Repeat the process until water pressure feels normal and the jets run smoothly—no gurgling, no air bubbles!

Manual Priming

If control panel priming doesn’t work, you can manually release trapped air using the pump’s bleeder valve.

1. Turn off the power at the circuit breaker to prevent electrical accidents.
2. Locate your Hot Tub pump and close the gate valve on the discharge side.
3. Slowly loosen the bleeder valve—you should hear air hissing out.
4. As soon as water starts flowing, tighten the valve back up.
5. Turn the power back on and test the jets again.

More Priming Tips

Still having issues? Try these troubleshooting steps:

• Clean your filter and check for blockages or leaks.
• Double-check the water level—low water can cause flow issues.
• Repeat the priming process if needed—it may take a few attempts.
• Never run your pump dry! If you’re unsure it’s fully primed, don’t let it run for more than 2 minutes. Running a pump without water can cause serious damage.

Troubleshooting Your Hot Tub Pump

Here are a few things that you can do to help sort a pump problem. More often than not, they are easy to fix and things that you can do yourself without having to get the professionals in.

Pump Won’t Prime

If you hear gurgling or bubbling sounds, air is likely trapped in your system. This often happens after refilling your Hot Tub. If there are no noises and you can’t prime the pump, the issue may be debris blocking water flow in the filter.

First, clean your skimmer basket and filter, then try priming the pump again. If the issue persists, you can “burp” the remaining air out by following these steps:

• Turn the heat down to prevent the heater from kicking in.
• Open all jets completely.
• Run the jets on high for about 15 seconds.
• Repeat this process three times, increasing the run time by 10-15 seconds each time.
• Continue until no more air bubbles appear and the jets run smoothly with normal flow.

No Water Pressure

If water isn’t moving correctly or the jets feel weak, trapped air or a physical blockage could be the cause. Just like the priming issue above, you’ll need to clear the system of any obstructions.

• Check the filters and skimmers for debris.
• Burp the tub to release any trapped air.

This should restore proper water flow and jet pressure.

Pump Motor Turns On and Off

If your pump is pulsing or randomly shutting off, you need to fix this issue quickly. The cause could be faulty wiring or an issue with the motor itself.

• Try resetting the breaker to see if it stabilizes.
• If the problem persists, use a multimeter to check if the wiring is supplying steady power to the motor.
• Inspect all electrical connections for rust or corrosion.
• If there are no external signs of corrosion, the issue may be inside the motor itself.

(I learned this the hard way when I accidentally filled my pump with water—not recommended, FYI!)

If the problem is internal, you might need to rebuild the motor. I tried this myself, but it didn’t work, so at that point, it’s best to bite the bullet and replace the pump.

Motor Runs, But Nothing Happens

If your motor turns on but there’s no water flow, your circulation system might have a stuck or clogged impeller. A telltale sign of this issue is a grinding noise, which means the impeller isn’t rotating correctly due to debris or an electrical problem.

To inspect the impeller, follow these steps:

• If your pump has a fan on the rear, turn off the power and remove the cover.
• Try rotating the fan by hand.
  • If it moves freely, the impeller is not blocked.
  • If it won’t rotate, the impeller is clogged.
• In that case, remove the pump’s front cover and clear out the blockage.

Pump Doesn’t Operate

If you turn on your pump and it doesn’t work and just hums it could be that the startup capacitor has blown. A quick way to check this is put the pump on high speed and you should find that it will run on high speed and then when you put it back to low speed it will run but will be “lumpy” and not make the right running noise.

This means that the startup capacitor has failed. Look for visible signs like bulges or black areas on the unit. Be very careful when you disconnect them as the capacitors job is to store charge and it will give you a nice belt of an electric shock if it is still charged and you bridge the connections.

They are easy to fit and inexpensive too so if this is the case, it is a quick fix.

Water Leaks

It may seem pretty obvious but you don’t want any water leaks around the pump or electrical components. This will cause corrosion and part failure over time. Water and Electric = tripping of your circuit breaker so it is a sure sign something isn’t right if that breaker will not stay on.

Check regularly for leaks in the tub. They operate at high pressure so even the smallest of leaks when the pumps are running at full capacity can become a problem.

Pump it up!

Sometimes, there is just no other option but to replace the pump. If this is the case, you need to remember that pumps are not all the same. Wherever possible, you should look to replace like for like. Here are some of the things that you need to check.

What Size Hot Tub Pump Do I Need?

See if you can find this information on the pump label. If you can’t try and find a model number etched into the pump and then search for the specs online.

Size of Frame:

Measure between the bolts. Remember, a 48 frame is less than 4 inches, and a 56 frame is greater than 4 inches.

Speed:

Calculate how many GPMs you need for your jets to operate optimally by multiplying by their flow rate the number of jets your Hot Tub has. For these details, look up the manufacturer of the jets – manufacturer Waterway is always a good start!

Voltage:

It is 110-120 volts if your pump has two wires in the power supply. You need a 220-240 volt pump if it has four wires.

HP:

Overdoing it with HP can cause problems, so keep an eye closely to the horsepower of your original pump. The general rule of thumb is not that the you should not be increasing your pump power by more than 1HP from the original.

Plumbing Size:

Calculate the PVC pipe diameter that goes to the discharge and intake of your pump to decide the union size you need. 2” and 2.5” are the most common on Hot Tubs.

Installing Your New Hot Tub Pump

It’s pretty easy to mount the replacement pump if you make sure you buy the right replacement and you don’t have any other issues with your Hot Tub.

Important: Be sure to flip the breaker so you won’t get a shock before you even start. Safety first!

1. Close the gate valves or empty your Hot Tub, so when you remove the pump, all the water won’t flow out.
2. With some towels or a Shop-Vac, be ready as a few gallons can spill out of the pipes.
3. Detach the wire with copper grounding.
4. Loosen the fixtures for intake and discharge.
5. Remove the bolts in the frame.
6. Slide the pump out gently so that you can reach and disconnect the power cables.
7. Fit the new pump doing the steps above in reverse.

Don’t Be A Chump, Take Care of Your New Pump!

Regularly check for debris buildup around the impeller. Inspect for leaks and repair them immediately. Well-maintained pumps can last a lifetime!

 Happy Tubbin’! 

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Thanks - Andi

 

Hi, Andi here. I own Buildahottub.com 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.

Fast forward to 2025, I've helped over 1400+ 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