The Ultimate Guide to All Things Hot Tub Pump


It’s amazing how little consideration you’re likely to give your Hot Tub pump when it works correctly. Arguably, this is the most critical part of your Hot Tub. Without it, you have just got a really large bath in your backyard! As it operates, it circulates the water in your tub. First, through the filter to clean it, then the heater to heat it and then eventually back into the Tub through your jets as the pressure builds.

What if you turn the Hot Tub on and you hear a screeching sound? Or, your jets kick in, but there is hardly any water going into them? Perhaps even worse, nothing happens at all, and the pump is just humming. Anyone for a cold tub? Didn’t think so!

It is important to know how to recognize signs of pump trouble. Perhaps more important is to know what steps to take to avoid problems and what to do when they do occur.

What’s in a Hot Tub Pump?

Make yourself familiar with the specifications of your Hot Tub pump before you attempt to repair or replace a malfunctioning pump. Most pumps have some form of specification written on them such as horsepower (HP) and speeds. There are other specs you might see such as discharge, inlet size and maximum head height. The most important thing really is the horsepower.

Variable or Single Speed

A pump that can control the jets and circulate the water is required for any Hot Tub. This implies that both high and low speeds are needed that are measured in revolutions per minute (RPM.) It’s called a variable-speed or two-speed pump when a single pump can move between high and low speeds.

Some Hot Tubs have single-speed pumps, but there are two pumps in those situations. One is called the circulation pump, which requires less energy than most other pumps and operates at a much lower speed. Circulation pumps only move between 25 and 35 gallons per minute (GPM) and have a low horsepower usually between 0.3-0.5 HP.

Even small variable-speed pumps drive 100 GPM or more. As much as 260 GPM can be pushed by the most powerful variable speed Hot Tub pumps.

At a higher rpm, the second pump will work to control the jets in your Tub if you have a two pump setup. The summary in this section is that your Hot Tub needs both water circulation and a higher speed pump (or mode) for the jets to work.

Wet and Dry Ends

It could completely destroy the pump if water were to reach the motor portion of your Hot Tub pump. Unfortunately, I know this through first-hand experience. Submerging your pump in water is not the best idea. In fact, you’ll need to replace it once it rusts – I did  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. In a sealed housing that protects it from moisture, the dry end contains the “engine”. Each end contains parts which can fail and cause problems with the pump.

For instance, you’ll see flow issues if your impeller gets stuck due to residue, debris or hair. If the motor wiring shorts (as what happened on mine!), it may cause your breaker to trip, seemingly at random. It is possible to fix each end separately when one part has a problem. But most of the time, replacing the damaged pump completely is less costly and saves you a great deal of messing around and time!


In order to operate, the “engine” in your Hot Tub pump requires fuel. It is important to know if you need 110-120 volts or 220-240 volts. Its 110-120 volts if your pump has two wires powering it. Usually, the two cables are green and white.

If it’s 220-240 volts then it has four wires. The wires will be gray, white, red, and black which is the US specification. In Europe the colors can be different. The voltage of your pump should be written on the specs on the unit itself. What you don’t want to be doing is under powering your pump as that will damage it. For example, if you have not stepped up your US 110V domestic supply you will not be able to run a 220V pump! I would note here that most Hot Tub components are 240V so do check the specifications.


The horsepower (HP) in your Hot Tub pump, much like the imaginary horses in your car engine and refers to how much power it produces. Hot Tub pumps range widely from 0.3 HP to 5 HP and everything in between and some!

You can’t just pop a pump of 5 HP into any Hot Tub and expect stellar jet action. Suitable plumbing must handle the pressure and the forces created by the pump. Too much power can restrict flow in pipes that are too small and may even cause leaks as the pressure would be too much.

What you will find though is that some pump’s ratings are actually somewhat over-rated. They specify the power that can be achieved at the factory and this is not really the power that it is going to produce in your backyard. So you do have a little leaway.


The discharge orientation is the position on your pump where water exits and it will either be in the middle, on top, or on the side of the Hot Tub pump. You’ll probably need to check the specifications on this one as by looking at a pump, you cannot tell which way the water flows through it – they all look the same! That said, you can obviously trace the pipe work and look for the pipes that connect to the drains and skimmer – this will be the inlet.

Tip: For the discharge, some pump manufacturers use non-universal fittings. If this is the case with your new pump, when you install the pump, you will need to replace the joints. You might need some plumbing reducers or converters to get the pump connected into the pipes.

Frame Size

There are pre-drilled holes in the housing around your pump where it will be bolted into place inside your Hot Tub. Depending on the size of the frame, the holes are further apart or closer together, so you would not be able to connect it correctly if you select the wrong size frame.

Either 48 or 56 are Hot Tub pump frame sizes. You should be able to locate one of those numbers on the sticker on your pump. If not, you can easily measure the distance between the bolts. It’s a 48 frame when the bolts are closer than 4 inches. It’s a 56 frame if the gap is over 4 inches.

How to Prime Your Hot Tub Pump

Air can get stuck in your circulation system when you add water to an empty Hot Tub. Priming the pump forces the air out of it so that water can flow properly. When using it for the first time after refills, and as needed in between, you’ll have to prime your pump.

Even self-priming pumps would need a helping hand sometimes. As the method of priming varies slightly from model to model, you’ll want to look for details in your manual. The two simple techniques are really easy to do.

Control Panel Priming

You can get your pump ready to rock and roll with the push of a button (or some pushes of a few buttons really!).

  1. Find your control panel’s priming mode (if it is available).
  2. For 10-20 seconds, power your jets off.
  3. For another 10-20 seconds, move your jets on full.
  4. Repeat until the water pressure is natural, and without gurgling or air bubbles, the jets when they are operational.

Manual Priming

You can use your pump’s bleeder valve to get rid of air if the first strategy doesn’t work.

  1. To prevent accidental contact with electricity its always best to flip your circuit breaker.
  2. Access your Hot Tub pump and on the discharge side, close the gate valve.
  3. Turn the bleeder valve slowly until you hear some air hissing out.
  4. Tighten the valve back up as soon as you start to see water flowing out of the valve.
  5. Time to try the jets again. Turn on your breaker and try the Hot Tub.

More Priming Tips

You can try a few other tactics if you’re still having issues after priming your pump:

  • Give your filter a good clean and search for other water flow problems such as blockages or even leaks.
  • Make sure that the tub is fully filled. Double check the water level. If the level of the water is too low, you can have water flow issues.
  • If you tried priming once and it didn’t work, try it again – don’t just give up! It often takes a few goes to correctly prime the pump. If you are not sure it’s totally filled with water, never run your pump for more than 2 minutes. The pump could be affected by this and they are not designed to be run without a load on – eg water. This is also called running a pump dry – don’t do it!

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

This can mean that you have air trapped in your system if you hear gurgling or bubbling sounds. Most often, this happens right after your Hot Tub is refilled. More often than not, this can be caused by debris in your filter if you are not able to prime the pump and there are no noises. Basically, the water flow is blocked.

First, clean your skimmer basket and filter, then try to prime the pump once again. If the issue continues, by turning the jets on and off, you can “burp” the rest of the air out of your Hot Tub.

  1. Turn the heat down, so the heater will not keep trying to kick in.
  2. Completely open all your jets.
  3. Run the jets on high for approximately 15 seconds.
  4. Do this three times, repeating the jet bursts and each time increase the run time by 10-15 seconds.
  5. Keep doing this until there are no more bubbles of air coming out and your jets are running continuously with normal flow.

No Water Pressure

Water not moving correctly? Jet’s not as powerful as they should be? The culprit could be trapped air. As with the situation above, you need to get the air out of the system or whatever is physically blocking the water flow. Check filters, skimmers and then burp the tub.

Pump Motor Turns On and Off

If your pump is pulsing or turning on and off, you need to address this issue quickly. It may be defective wiring or the “engine” itself if the temperamental motor does not begin to behave with a simple breaker reset.

You can use a multimeter to verify whether the wiring is actually supplying steady power to the engine if you are comfortable doing so. Look for rusty or corroded connections – it does happen over time. If there are no visible external signs of corrosion, it could be in the motor itself – this was the problem I had after I filled it with water – not recommenced FYI!

If the issue seems to be internal, you may need to fully rebuild the motor. I tried this and it didn’t work for me so it might be time to bite the bullet and order a new pump.

Motor Runs, But Nothing Happens

If you can turn it on, but your water isn’t flowing, somewhere in your circulation system you might have a stuck impeller or a clogged up one. Grinding noises are a hallmark indication that your impeller does not rotate correctly because of debris or an electrical problem.

You are going to have to do some physical inspection on this one. If your pump has a fan on the rear, see if you can remove the cover and then rotate the fan with your hand. Turn off the power of course first! If you can rotate it freely with your hand then the impellor is not blocked. If you can’t, then it is and you will need to remove the front over of the pump and unclog the impellow.

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.


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!


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.


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!

Check it regularly for buildup of debris around the impellor and of course any leaks need to be repaired. Well maintained pumps will last a lifetime!

Happy 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

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