A clean and working spa or hot tub filter cartridge is essential for maintaining normal levels of chemicals in pool water. Cleaning and replacing filters on a regular basis is actually a simple task required to limit bacterial growth and extend the life of individual spa components. Fortunately, for pool owners, it's as simple as removing, rinsing, and replacing the filter.
Steps
Part 1 of 4: Remove the Spa Filter

Step 1. Locate the filter cartridge
Often times, the filter can be seen partially from inside the spa system. It is usually located inside a container, support or lid. If you don't see such a compartment, check your user manual to locate the filter.

Step 2. Turn off the spa system before removing the filter
Since the parts of the spa systems work together to achieve filtration, you should not operate the spa without the presence of a filter cartridge.

Step 3. Turn the filter to the left
Move slowly and smoothly to avoid damage. As you turn the filter, examine it for lower threads that may also need to be unscrewed. If this loosens the filter, pull it up and out of the compartment.

Step 4. Check the user manual
Although many styles of cartridge filters are easily removed with a counterclockwise twist, not all are removed so simply. If a gentle twist doesn't loosen the filter, let the user manual guide you through the removal process.
Part 2 of 4: Perform a weekly cleaning

Step 1. Inspect the filter for damage
If you see tears or feel that the center element is loose, do not continue cleaning the filter. Be sure to replace damaged filters to avoid damaging other items in the spa, such as the nozzle lines, which can become prone to debris build-up.

Step 2. Rinse the spa filter with a filter cleaning rod
Look for a cleaning wand that attaches to your garden hose and comes equipped with soft teeth like a comb. Hold the nozzle at a 45-degree angle and use the comb to gently pry open and rinse debris from the spa filter pleats.

Step 3. Add a drop of enzyme-based products to the water
Enzymes prevent the formation of biofilm (the sticky, tar-like layer of bacteria that sometimes grows in pools and spas) by breaking down oils and other contaminants that create the conditions for bacteria to grow. Adding a weekly dose of cleaner directly to the water keeps the filter clean by preventing the formation of a foamy ring of oils around the filter core.

Step 4. Inspect the filter for debris
Gently part the filter pleats and examine for a build-up of dirt or large debris. Scoop out and throw away the long pieces of debris.
Part 3 of 4: Perform a monthly cleaning

Step 1. Fill a large plastic bucket with water
Typically 5 gallons (20 liters) is the amount of water needed to fully submerge a spa filter. Don't worry about the water temperature. Hot water cleans faster, but cold water will clean the filter just as well.

Step 2. Add a mild cleanser
Follow the directions for your brand of spa filter cleaner to determine how much to add for every 1 gallon of water.
Do not use anything other than filter cleaner to clean the filter. Some people choose to use bleach or detergent to clean filters, but these harsh chemicals can damage filters or cause problems with the water chemistry

Step 3. Repeat the weekly cleaning steps
Before treating the spa filter with a cleaner, be sure to protect the spa by turning it off and visually inspecting the filter for damage. Spray with the cleaning wand attached to the hose to remove stubborn debris.

Step 4. Soak the filter
If you used hot water, soak it for 1 hour. If you filled the bucket with cold water, let the filter soak overnight.
Remember to keep the pool off while the filter is soaking

Step 5. Rinse the filter with a cleaning rod
Once it's soaked, be sure to rinse it well to remove any remaining chemicals or debris. Remember to hold the cleaning rod at a 45 degree angle to prevent dirt from getting into the core.

Step 6. Clean the water
Follow the hygiene instructions outlined in the user manual by adding cleaning chemicals directly to the water. Improper cleaning and water chemistry can lead to the growth of algae and bacteria that can make you sick. Excess debris can damage the components of your spa system and shorten the life of the filter.

Step 7. Be patient
Taking the time to carefully clean the cartridge will ensure that you remove as much debris as possible, which in turn will extend the life of the filter. Plus, doing a thorough cleaning this time will make the next round of cleaning even easier.
Part 4 of 4: Replace the filter

Step 1. Make sure the filter is white
If you are replacing a freshly cleaned filter, it should be white and free of debris. If it's stained black or covered in a slimy residue, don't put it back in your spa system.
You need to install a new filter every one to three years, so you are likely to run into an unusable filter at some point. It's a good idea to save an extra filter for when it needs to be replaced

Step 2. Slide the filter into place
Simply reverse the removal process to replace the filter. For most filters, sliding it back into its compartment will require turning it clockwise.

Step 3. Turn on the hot tub
Once the filter is installed, allow the spa to run for a full cycle before using it. This will deplete any debris that might have accumulated while the spa system was not actively filtering the water.