Why is My Hot Tub Pump Surging? (Here’s How to Fix It)

By James Brockbank •  Updated: 04/11/21 •  13 min read

Why is my hot tub pump surging?

A surging hot tub pump happens when the pump in your hot tub stops functioning as designed. The problem is usually diagnosable by the pulsating of the hot tub pump. The cause of a surging pump relates to filter problems, water levels, clogged lines, airlocks, and worn-out pumps. When you observe an irregular rate of water output from the spa jets, then it’s very likely that you have a surging pump.

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A few months ago I noticed that my hot tub jets were not working properly. They seemed to be pulsating. It turns out that some leaves were clogging up one of the lines to the pump.

I did some more research on surging hot tub pumps, this is what I found…

It would help if you fixed a surging pump soon as it is detected because it can lead to several other problems.

For instance, failure to detect and fix the surging hot tub pump can affect the pH levels because insufficient water passes through the filters to other parts of the system.

Check out our article on hot tub pumps not working for more information on what can be done to troubleshoot your spa.

Let’s get started!

What Causes a Surging Hot Tub Pump?

A hot tub pump surging has different causes, including: 

  1. Filter problems
  2. Incorrect water levels
  3. Clogged lines
  4. Worn out pumps
  5. Airlocks
  6. Scale Buildup

Filter Problems

If your hot tub has a problem with the filters, a surging pump can occur. A filter is a critical component of the hot tub system. It’s designed to trap and remove scum and any dirt in the hot tub water. This function is essential because it helps to maintain the desirable pH levels of the hot tub water. The maintenance of the water pH is necessary for the proper functioning of all types of hot tubs. Specifically, allowing dirt to accumulate in the filters can cause pump surging and pulsating.

Check out our full article on how to clean your hot tub filters for more information.

To clean your filters, I recommend the Leisure Time O Filter Cleaner.

I recommend the Aquatix Pro Cleaner to get the dirt and debris out of the filters.

Incorrect Water Levels

The water level could be another cause of surging in the hot tub. This could be the cause of pump surging if you did not find a problem with the filters. When the hot tub’s water level goes below the recommended levels, then air can start getting into the hot tub’s pump system through the jets. In such a case, hot tub pump surging occurs as the pump struggles to pump the air instead of water.

Clogged Lines

Clogging of the pump along with the water line is another possible cause of pump surging. The cause of clogging along the line is caused by dirt-build up. It’s not easy to detect or fix this problem. Still, there’s usually no alternative other than to drain the spa and suck out the dirt with a shop vacuum.

Check out our full article on how to clean a hot tub for more information.

I recommend the Stanley 12 Gallon Wet/Dry Vacuum to get the job done.

Worn Out Pumps

If you have inspected your hot tub pump surging from the above areas and found no problem, then your hot tub pump may be worn out. Pumps will usually start to pulsate when they near the end of their service life. If you have been using the pump for more than five years, you might consider replacing it with a new one.

I recommend a couple of different hot tub pumps, depending on what size you will need for your spa. Some of them are listed below.

KL KEY LANDER Hot Tub Spa Pump, 1.5HP, Two Speed, 48Frame LX Motor (115V/60Hz); 2″ Port; OEM Model #37334-03; 48WUA1001C-II

NEW KL Key Lander Hot Tub Spa Pump, 4HP, Two Speed, 56Frame LX Motor (220-240V/60Hz); 2″ Port; OEM# #0982601-03; 1431601-03 and 56WUA400-II

Waterway Plastics 3722021-1D Executive 56 Frame 5 Horsepower Spa Pump, 230-Volts


Airlocks are formed if you have recently filled your hot tub and there is very little or no pressure coming from the jets. The development of airlocks in your hot tub interferes with the regular operation of the jets. It decreases the ability of the pump to push water through the main lines.

Scale Buildup

Improper functioning of your hot tub could result from scale buildup. The effect of the scale buildup may not be immediate. Instead, it will take time before you start noticing a decline in your hot tub’s performance.

One of the warning signs is the increased difficulty in adjusting the jet nozzles. The problem could be caused by lime and calcium deposits forming on the rings of your jet nozzles. The same buildup could be taking place in your hot tub plumbing and pump system. Thus, you may notice a lower pressure or decreased output from the water jets.

I recommend Leisure Time Defender to treat your hot tub to prevent scale buildup inside the hot tub and electrical components.

How to Fix a Surging Hot Tub Pump

The hot tub pump surging issue is only challenging when you are detecting the cause of the problem. Once you know what is causing the surge, fixing the issues is usually straightforward.

You need to remove and clean the filters correctly, replace old pumps, clean the debris out of the spa, and remove any airlock in the system.

If the problem with your hot tub was low water levels, refill the hot tub to the required levels. However, you can get complications if the low water level is arising from hot tub leakage. Ensure you fix the hot tub leakage issue before refilling the hot tub with water.

Clogging in the pump line is resolved by removing the dirt the same way I do with the filters. However, this can take a little longer than it does for the filters. The most challenging part is to locate the clogged area. After finding the debris, it should be removed through either draining or carefully cleaning the hot tub.

For some more information, check out this great article from Arctic Spas on spa pump maintenance.

How Do I know If My Hot Tub Has an Air Lock?

The airlock is a common problem in hot tubs. But fixing airlocks is not complex. Airlocks occur when there is a sharp drop in the water pressure from the jets. It happens when you change your hot tub water, trapping air in the pump or the lines. Hot tubs have sensors that help with detecting the waterline and the water flow pressure. This prevents the hot tub heater from turning on when there is no water flow in the heater.

Airlocks affect the proper functioning of the jets. Therefore, the most common airlock indicator is the failure of the jets to function correctly. When water is not coming out of the jet, your pump might be affected by an airlock. Still, the production of a humming sound from the pump or the jet is an airlock indicator in a hot tub.

How to Fix a Hot Tub Air Lock

To fix an airlock inside a hot tub, you must first turn the water temperature down by at least 10 degrees. Next, set all the jets in the spa to their open positions allowing for maximum water flow. Finally, turn on all the pumps until the water pressure returns to normal. The pumps may require 2 to 3 cycles before the water pressure returns.

The heat from the pumps will warm up the water, so turning the temperature down is good practice.

Airlocks are formed if you have recently filled your hot tub and there is very little or no pressure coming from the jets. The development of airlocks in your hot tub interferes with the regular operation of the jets. It decreases the ability of the pump to push water through the main lines.

Luckily this problem is not complicated to fix.

How Do You Purge Air From a Hot Tub Pump?

Purging air from the hot tub requires you first to open all the jets completely. You are required to turn the jets on high for 10 to 15 seconds before you turn them off again.

From this point, you are required to turn on/off the jets continuously at intervals that increase their running time by ten seconds for every round. The process should be allowed to continue to the point where you’ll start seeing air bubbling out from the jets. I usually advise leaving the jets running for as long as there’s bubbling.

When no bubbles appear in three rounds of turning the jets on and off, you could use a different method to purge the air. You can locate the spa pump and the union nut between the hot tub’s motor and plumbing. Loosen the union nut to allow the release of any trapped gases. After all the air has leaked out, water will start flowing normally. However, it would help if you waited for the stream of water to become steady before you can retighten your union nut. You can also turn the jets on again to ensure that they have started functioning correctly.

How Long Should a Hot Tub Pump Last?

A hot tub pump has an average life of between 5 and 10 years. The maximum duration of the service life is primarily affected by the care and maintenance of the pump. I usually advise caring for the hot tub pump thoroughly to ensure they offer the maximum service life. Other than prolonging the pump’s life, proper maintenance of the hot tub ensures that you enjoy the hot tub more.

You can check your hot tub regularly for maintenance needs and conduct the necessary routine care to prevent affecting the hot tub. For instance, you can prolong the pump life by maintaining the water balance of your hot tub regularly. Maintaining a chemical balance eliminates the chances of the scale build-up in the hot tub water that could affect the pump functioning directly.

You should also check the hot tub filters’ condition to ensure they are not clogged or worn out. Blocked and worn-out filters do not work correctly in filtering the hot tub water. This can overwork the pump and cause it to wear sooner than designed. Ensure that the hot tub pump’s location is in the right area where dirt and debris do not collect. I also advise that you keep listening to your pump for any grinding, whining, or humming sounds. Worn-out bearings usually produce these sounds. Airlocks and blockage can also make the pump produce such sounds. I encourage you to observe these measures if you want to prolong your hot tub pump’s service life.

spa tool kit

Is There a Reset Button on a Hot Tub Pump?

The high limit reset switches are not contained in the hot tub pumps. The controls are mainly used with the heaters when the hot tub stops working. But there is an alternative solution to stripping for the pumps. Instead of just flipping the switch, a hot tub pump is usually reset by following specific steps.

First, you should locate the high limit switch. The switch is usually a red button at the pump or the spa pack. Press the button to click it into place. That’s the only thing you need to do to reset the hot tub pump successfully. Your hot tub will be ready and safe to turn on again for use.

My Hot Tub Pump Only Works on High Speed

I have seen and heard complaints from the people whose hot tub pumps work at high speed. This is a common problem you can also face with your hot tub. Before it happens to you, we’ll tell you the common causes of the problem.

First, your hot tub pump could be running at high speed alone because of thermostat settings issues. If you set the thermostat incorrectly, you could find the hot tub pump working at high speed alone. But you can fix the problem by locating the timer clock and rotating it to adjust the thermostat to the correct reading.

Another problem could be throwing off the power levels at high and low speeds. I usually advise checking the power levels at either 110v or 220v with a range of 10 percent less or more.

Thirdly, the air switch of the hot tub could be the cause of the problem. Therefore, you need to check the air switch button used for switching speeds. If this is the cause, fix it by using the voltage coming in and out.

The final possible cause of the problem is the clogging of the switch. The problem occurs in the hot tub pumps that use a mechanical switch button. Make sure that you check for clogging and resolve the issue if detected. You can also check whether your hot tub’s mechanical switch is stuck in a high position because of insects or broken components and fix it accordingly.

My Hot Tub Pump Only Works on Low Speed

On the contrary, your hot tub pump could be working only at a low speed. What could be the problem?

One of the reasons that your hot tub pump runs at low speed alone is disconnection or crimpling of the air hose. Besides, an incorrect attachment or reversal of the wires could be the problem. The problem may be expected in cases where you have recently replaced the hot tub’s pump. 

Another problem could be an issue with the switch at the hot tub’s back pump motor. The switch could be stuck at a low-speed setting. However, you should also check the switch for possible blockage and malfunctioning.

The last issue you need to check is a possible issue with the contractor that changed the pump’s speed. Ensure you check the connections to confirm they are secure.

Check out our full article on troubleshooting hot tub jets not working for some more information on hot tub maintenance.

Hot Tub Pump Surging: Conclusion

hot tub pump surging

Pump surging is caused by filter problems, incorrect water levels, clogged lines, airlocks, and worn-out pumps.

You should also locate and unclog the blocked pipes if they are the cause of surging. You can detect a pump airlock by the failure of the proper functioning of the jets. When you have an airlock, you need to resolve it by purging the air out.

A properly maintained hot tub pump can last for 5 to 10 years, depending on how well you maintain it.

Check out our article on leaving a hot tub on all the time for more information on maintaining a hot tub.

I hope you found this article helpful on “why is my hot tub pump surging?”

James Brockbank

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