Expert Hot Tub Filters Guide - Everything You Need To Know

Published on

April 16, 2023

Hot tub filters keep your spa water free of debris and dirt. They have an essential role in reducing the risk of hot tub system damage and providing a pleasant breathing experience.

Most hot tub owners know the importance of using chlorine or bromine to keep the water clean, but what about filters? How often do they need cleaning? Do you need to replace them when they have deteriorated?

In this article, we explore the world of jacuzzi filters. We discuss filter types, how to clean them, and how and where to find an appropriate replacement.

Hot Tub Filters - What Are They?

Spa filters are essential components of hot tub filtration systems. Their role is to purify the spa water by keeping dirt and debris away. As a result, the hot tub's lifespan is extended, preventing a decrease in performance.

Jacuzzi filters remove a part of the bacteria from the water, but you still need to use chlorine[1] or bromine for a regular spa to prevent green or cloudy water. This is important, especially if the spa water has an unpleasant odor.

The Importance of Spa Filters

Spa water is often contaminated with bacteria[2] from body oils, but also with dirt, algae, and other impurities[3]. As a result, filters are essential to keep the water clear.

It is not enough even if you use chlorine to sanitize your hot tub. Dirt and debris are not dissolved by sanitizers.

While some filters are able to trap some types of bacteria, others filter chemical contaminants.

Even though filters don’t remove all bacteria from hot tub water, O-Care provides a solution for using up to 78% less chlorine and bromine. Our product helps you reduce the use of hot tub chemicals and to help your filter live longer.

How Spa Filters Work

Hot tub filtration systems work using one of two types of mechanisms: suction and pressure. Suction systems are the most common among hot tub owners, even though they are a bit larger. Regular maintenance is required, but it's easier compared to pressure systems.

The pump pushes the water into the filter and allows it to recirculate. By repeating this process throughout the day, the filtration system is what keeps your water free of impurities.

Spa filters trap impurities and don't allow them to go back into your spa water or into the pipes. 

The filter material can be made of:

  • Plastic
  • Paper
  • Fabric
  • Fossil algae powder
  • Ceramic
  • Sand
  • Fiber

Spa Filter Types

Filters for spas come in different types, depending on the manufacturer and the type of filtration system your hot tub has.

Here are the main jacuzzi filter types:

  1. Ceramic filters
  2. Cartridge filters
  3. Diatomaceous filters
  4. Sand filters

1. Cartridge Filters

Cartridge filters have the following characteristics:

  • They have a part made of folded paper, plastic, or fabric which allows water to pass, but confines dirt.
  • They are connected to the filtration system through a plastic part that houses the fabric.
  • They are the most common type of jacuzzi filters.
  • They filter impurities as small as 5 microns.

Cartridge filters are:

  • Suited for: Busy people who don't want to invest their time in spa filter maintenance.
  • Not suited for: spas with high-velocity water flow (commercial spas), because the impurities can penetrate the filter at high pressure. To solve this problem, you can lower the water flow to a minimum.

Pros of cartridge filters:

  • Price: they are the most affordable.
  • Ease of use: you can replace them in a few minutes.
  • You need to clean them twice a year.

Cons of cartridge filters:

  • Cartridge replacement frequency: high (every few weeks).
  • High maintenance costs because of high replacement frequency.
  • You can't recycle the filter cartridge, which makes them environmentally unfriendly.

2. Ceramic Filters

Ceramic filters have the following characteristics:

  • They are similar to cartridge filters but are made of a ceramic material capable of containing small particles because of their porosity.
  • They filter various contaminants, such as viruses, turbidity, bacteria, cysts, protozoa, and more. 

Ceramic filters are:

  • Suited for: large hot tubes because they clean larger areas than most hot tub filter types.
  • Not suited for: people who want to eliminate chemical residue from their spa water.

Pros of ceramic filters:

  • They don't remove healthy minerals from the water.
  • They are environmentally friendly, as they are similar to activated carbon.
  • They are more efficient than cartridge filters.
  • You can reuse them multiple times without replacing them.
  • They are suitable for both gravity water and under-sink water filters.

Cons of ceramic filters:

  • They are not efficient in filtering chemical contaminants. To eliminate this downside, some manufacturers include activated carbon blocks or ion exchange resin).
  • They easily crack if you drop them, which decreases their performance.

3. Diatomaceous Earth Filters (D.E. Filters)

Diatomaceous earth filters have the following characteristics:

  • They are a powder made of fossilized algae powder, capable of trapping impurities.
  • They have the capacity of cleaning small particles (4 microns).

D.E. hot tub filters are:

  • Suited for: pools and hot tubs that require high filtration efficiency.
  • Not suited for: people who look for less frequent maintenance. Because of their size and the use of hot water, D.E. filters need to be washed frequently, even daily for public spas.

Pros of D.E. filters:

  • They are the most effective type of spa filter.
  • Replacement frequency: low ( every three years).

Cons of D.A. filters:

  • Price: they are the most expensive type.
  • They are hard to clean.
  • They come with an environmental risk, which limits their use in certain areas.
  • They are carcinogenic if you inhale the power.
  • You need to make sure not to spill the powder into the pool or spa.

4. Sand or Fiber Balls Filters

Sand or fiber balls filters have the following characteristics:

  • They use sand to filter the water contaminants. More recent versions use the same system but have fiber balls instead of sand, as they are more efficient.
  • They are used for large hot tubs.
  • Sand filters trap particles that measure between 20 and 35 microns, while fiber ball filters can catch particles as small as 3 microns.

Sand or fiber balls filters are:

  • Suited for: commercial hot tubs, as you can automate the backwashing process.
  • Not suited for: drought areas because of the water waste during backwashing.

Pros of sand or fiber balls filters:

  • They clog less often than other filters.
  • Replacement frequency: low (5 to 7 years).
  • Ease of use: you need to change only the fiber balls every 2 years.
  • Environmentally friendly.

Cons of sand or fiber balls filters:

  • They become less effective over time.
  • Price: the initial investment is high.
  • Some brands require you to wash the fiber balls manually.

How To Sanitize Hot Tub Filters

A dirty filter is not as efficient in keeping dirt and bacteria away from your hot tub water. As a result, you need to clean them periodically to keep the water and the hot tub safe.

Here are the steps you need to take to clean a filter cartridge:

  1. Have a filter cleaning solution at hand.
  2. Check the user manual before removing your filter cartridge.
  3. Turn off the jacuzzi to avoid using it without a filter.
  4. Take the filter cartridge out.
  5. Inspect the filter cartridge and determine if it has deteriorated. If so, replace it.
  6. Rinse the filter cartridge using a garden hose.
  7. If the cartridge is extremely dirty, soaking it in a filter cleaning chemical will solve the problem.
  8. Take the filter cartridge out and rinse it again until you completely remove the chemicals.
  9. Let the filter out until it is completely dry.
  10. Place it back into the filtration system.

How Often To Clean Hot Tub Filters

Filter cleaning frequency depends on the type of filter you use and on your bathing frequency.

As most spa owners use cartridge filters, we recommend rinsing them twice weekly to ensure your filtration system works properly.

Related Reading: Hot Tub Water Maintenance: Best Expert Advice

Replacing Your Hot Tub Filter

Finding the exact replacement spa filter is complicated if you don't know the basics: filter part numbers and filter measurements. Understanding these key elements helps you choose the best replacement filter for your hot tub.

Is It Time To Change Your Hot Tub Filter?

You know it's time to change your filter cartridge when:

  • You see signs of wear or tear.
  • It is extremely dirty.
  • The water can hardly run through it.

How To Identify the Filter Part Number

You can easily identify what replacement spa filter you need by checking for the number on the top or bottom end caps. The part number is usually composed of numbers and letters.

There is a difference in part numbers, each is specific for every filter manufacturer. Even if the filters are identical, their part number differs.

In case you cannot find an identical filter in terms of a part number, we recommend you compare the filter dimensions.

How To Measure the Spa Filter

The best way to find the perfect replacement filter for your spa is to measure it.

Here is a list of the filter dimensions you need:

  • Length
  • Outer diameter
  • End cap configuration

Measure The Spa Filter Lengths

Follow these rules when measuring the spa filter length:

  • Measure the length of the filter from one end cap to the other.
  • Don't include threads, attachment points, or handles.
  • Start from the edge.

Measure the Spa Filter's Outer Diameter

Follow these rules when measuring the spa filter diameter:

  • Draw an imaginary line across the center and measure it.
  • Don't forget to consider the expansion or shrinkage of the filter that results from extensive use. This is usually around 1/16 inches.

End Cap Configurations

To find a suitable replacement filter, make sure to consider the main two types of threads: MPT and SAE. MPT threads are fine, while SAE threads are coarse.

After you identify your thread, measure the outer diameter of the cap, which is its widest point.

You also need to measure the inner diameter of the open-end cap. To do this, you need to leave out the thread and measure only the diameter of the inside part of the thread.

Are Spa Filters Universal?

No, spa filters are not universal. Although most jacuzzis use similar filters, they come in different shapes, sizes, and designs. This is why it is essential to know the part number or measurement of the filter before you engage in a purchase.

Hot tub filters last longer when using O-Care
Hot tub filters last longer when using O-Care

Hot Tub Filter Dealers Near Me

Here is a list of the most popular hot tub filter dealers:


In conclusion, hot tub filters play a crucial role in maintaining the cleanliness and longevity of your spa. It is important to understand the different types of filters available and to choose the one that is best suited for your hot tub model. Cartridge and ceramic filters are the most popular, while sand and D.E. filters are the most expensive. The type of filter you need depends on your spa model, as well as on the manufacturer.

Regular cleaning and replacement of filters is essential in keeping your spa water free of debris and dirt, and in preventing damage to the hot tub system.

By following the tips and guidelines outlined in this article, you can ensure that your hot tub remains in top working condition for years to come.

Want to use less sanitizer and ensure your hot tub filters last even longer? Consider using O-Care for your hot tub. You won't regret it!

Buy O-Care today!