When to replace hot tub filter cartridges depends on two things: age and condition. Most pleated cartridges last 12 to 24 months. Replace one sooner if the pleats are torn, flattened, or heavily stained, or if a thorough deep clean no longer brings back clear water and strong flow.
A hot tub filter catches the oils, dirt, hair, and debris that sanitizer can't remove on its own. When the cartridge wears out, that waste stays in your water. This guide covers seven signs a filter has reached the end of its life, how to decide between cleaning and replacing, how to deep clean a cartridge the right way, and how to pick the correct replacement.
Hot Tub Filter Care at a Glance
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Task |
How often |
|
Rinse the cartridge with a garden hose |
Every week for regular use; every 2 to 3 days with heavy use |
|
Deep clean with a spa filter cleaner |
Every 4 to 6 weeks (every 3 to 4 weeks with heavy use) |
|
Inspect pleats, end caps, and core |
At every rinse |
|
Clean the filter and flush the plumbing |
At every drain and refill, about every 3 to 4 months |
|
Replace the cartridge |
Every 12 to 24 months, or sooner if damaged |
How a Worn Filter Affects Your Hot Tub Water
A worn or clogged filter hurts both water quality and performance. It can't trap dirt, body oils, hair, and other debris, so those contaminants keep circulating, leaving the water cloudy and harder to keep clean. A clogged filter also restricts circulation. The pump works harder, and less water moves through the heater.
As a result, you may notice weaker jets, slower or uneven heating, flow error codes on some spas, and trouble holding sanitizer levels. Regular cleaning and timely replacement keep the water clear, the circulation steady, and the equipment running efficiently.
7 Signs It's Time to Replace Your Hot Tub Filter
1. The Pleats Are Torn, Frayed, or Flattened
The pleats are the cartridge's filtering surface. Once they tear or flatten, the filter has less area to catch debris, and no amount of rinsing can fix that. After your weekly rinse, inspect the pleats closely. Frayed edges, gaps, pleats that no longer spring back, or sections that stay pressed together mean the cartridge is done. Check the plastic end caps and center core too. A cracked cap lets water bypass the media entirely.
2. Stains Will Not Rinse Out
Heavy staining means oils, lotions, and minerals have worked deep into the material. A weekly rinse with a garden hose, working from the top of each pleat down, keeps a healthy filter looking fairly clean. Light discoloration over time is normal. If dark or heavy stains remain after a deep clean with a filter cleaner, replace the cartridge. Gray, crusty buildup is often calcium scale. If scale keeps returning, a sequestering product such as SpaGuard Stain & Scale Control helps protect the new filter.
3. Cloudy Water Keeps Coming Back
Cloudy water has several causes, so work through the basics first:
1. Test the water and balance alkalinity first, then pH, using our water testing supplies.
2. Clean the filter.
3. Shock the water with a product from our hot tub shock collection.
4. Add a hot tub water clarifier if needed, then rinse the filter after the clarifier has had time to work.
If the water clears and then turns cloudy again within days, while the chemistry stays balanced, suspect the filter. If it never clears, the water itself may be worn out. See our guide to the signs your hot tub water needs to be drained.
4. Jet Flow Feels Weak
A clogged filter restricts water flow through your spa. If the jets feel softer than they used to, clean the cartridge first. If a freshly cleaned filter still leaves the jets weak, the pleats are likely packed with buildup that cleaning can't reach. A new filter lets water pass freely again. If a new cartridge doesn't restore flow, look for other causes, such as a closed valve, an air lock, or a pump problem, and contact a qualified hot tub technician if needed.
5. Sanitizer Drops Fast and Odor or Foam Returns
A filter that no longer traps waste leaves more oils and debris in the water. Your sanitizer then spends its strength on that waste instead of keeping the water safe.
Watch for these patterns:
· Chlorine or bromine readings that fall quickly after you add sanitizer
· A strong smell that returns soon after you shock the water
· Foam that keeps coming back, even after you use a hot tub defoamer
Each of these can have other causes, so retest the water too. If the chemistry checks out and the symptoms continue, check the filter. A steady sanitizer system also helps. The FROG @ease system holds chlorine at a low 0.5 to 1.0 ppm and uses up to 75 percent less chlorine than traditional methods, but it still depends on a clean filter to work its best.
6. The Cartridge Is 12 to 24 Months Old
Take age into account even if a filter looks acceptable. Most cartridges should be replaced every 12 to 24 months, depending on how often you soak. Heavily used tubs land at the shorter end, and lightly used tubs at the longer end. Write the installation date on the end cap with a permanent marker. Once it reaches the one-year mark, start checking the pleats more closely.
7. Cleaning Stops Making a Difference
A deep-cleaned filter should restore better flow and clearer water. If you clean the cartridge and see no change, the damage is likely beyond what a cleaner can reverse. Another clue is a filter that clogs again soon after every cleaning, or one that still smells after a thorough clean. At that point, a new cartridge costs less than the time and chemicals you spend fighting the old one.
When to Replace Hot Tub Filter vs. When Cleaning Is Enough
Clean the filter when it's dirty but intact. Replace it when it's damaged, stained, or old.
|
Clean it when |
Replace it when |
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The pleats are whole and hold their shape |
Pleats are torn, frayed, or flattened |
|
Oils and grime are the main problem |
Stains remain after a deep clean |
|
It has been 4 to 6 weeks since the last deep clean |
The cartridge is 12 to 24 months old |
|
Flow improves after a rinse |
Flow stays weak after a deep clean |
|
The end caps and core are intact |
An end cap or core is cracked or loose |
How to Clean a Hot Tub Filter Before You Decide
A proper deep clean tells you whether the filter has life left. Turn the spa off at the control panel, and ideally at the breaker, so the pump can't start while the filter is out. Then remove the cartridge and follow these steps:
1. Rinse off loose debris with a garden hose at moderate pressure, working top to bottom between the pleats.
2. Spray the pleats evenly with a spa filter cleaner, or soak the cartridge in a diluted cleaner solution.
3. Let the spray sit for about 15 to 20 minutes, or follow the product label.
4. Brush lightly with a soft brush if oil or scale buildup is heavy.
5. Rinse thoroughly until no cleaner or foam remains.
6. Reinstall the cartridge, or let it dry fully and swap in a clean spare.
What to avoid:
· Pressure washers and high-pressure nozzles, which can tear the fibers and seams
· Dishwashers and washing machines, whose heat can warp end caps
· Bleach, household cleaners, and laundry or dish detergent, which can damage the media or leave residue that foams in the spa
· Running the spa without a filter, even for a short time
SpaGuard Filter Cleaner is a 1-quart spray bottle made for spa cartridge filters. It removes body oils, dirt, grime, grease, and scale, and SpaGuard recommends using it every 4 to 6 weeks. For a deeper clean, soak the cartridge for about an hour in 1 part cleaner to 3 parts water. Use it outside the spa, never in the water, and wear gloves. Other options include Sirona Spray & Rinse Filter Cleaner, which turns blue on contact so you can see your coverage, and ProTeam Spa Filter Cleaner, which works as a spray or a soak.
When you drain and refill, run SpaGuard System Flush through the plumbing first. It loosens buildup hiding in the lines, so it ends up on the old filter instead of in your fresh water. Then clean or replace the cartridge.
How to Choose the Right Replacement Filter
Filters that look alike can differ in length, diameter, and fittings. A poor fit lets water bypass the media. Before you order:
· Match the part number. It's usually printed on the end cap or listed in your owner's manual.
· Measure the cartridge if the number has worn off: overall length, outside diameter, and the size of the center opening.
· Check the fittings on the top and bottom, such as threaded, open, or closed ends, plus any handle.
· Match the square footage of filter area your spa calls for.
· Choose genuine filters when your manufacturer requires them. Marquis, for example, specifies the Marquis Spas Replacement Filter 50 Sq Ft Threaded #20690 for many Crown, Elite, and Celebrity Series hot tubs.
Keeping a second cartridge on hand makes maintenance easier. You can swap in the clean spare and keep soaking while the other one dries. Letting a filter dry completely between uses can also help it last longer.
Ready to Replace Your Hot Tub Filter?
Once you know when to replace hot tub filter cartridges, a spare and a bottle of cleaner keep upkeep simple. Shop our hot tub filter cartridges collection, and browse hot tub cleaning and maintenance supplies for everything else your spa needs. Online orders over $50 ship free in the USA, and orders placed before 3 p.m. Monday through Saturday ship the same day.
Check your filter regularly for signs of wear, damaged pleats, or buildup that cleaning can't remove. Replacing a worn filter on time keeps water circulating properly and keeps your hot tub cleaner between maintenance sessions.
Conclusion
A hot tub filter shows clear signs when it's about to fail: torn pleats, stubborn stains, recurring cloudy water, weak jets, sanitizer that burns off quickly, an aging cartridge, and cleaning that no longer helps. Replacing the cartridge when needed keeps the water cleaner and protects the pump and heater behind it.
This weekend, pull your cartridge and check it. If it's still in good shape, give it a deep clean. To build other habits that protect your spa, read our 10 tips to keep your hot tub clean and safe and browse our full range of hot tub chemicals and supplies.
Frequently Asked Questions
How often should you replace a hot tub filter?
Replace a hot tub filter every 12 to 24 months, depending on how often you use the spa. Replace it sooner if the pleats are torn, flattened, or heavily stained.
Can you clean a hot tub filter instead of replacing it?
Yes, if the cartridge is intact. Rinse it weekly and deep clean it every 4 to 6 weeks. Cleaning won't fix torn pleats or remove heavy stains, so you'll need a new cartridge in those cases.
What happens if you do not replace a worn hot tub filter?
A worn filter can't trap debris, so contaminants keep recirculating through the water. It can also restrict flow, which makes the pump and heater work harder.
How do I know which replacement filter fits my hot tub?
Match the part number on the end cap or in your owner's manual. If it's worn off, measure the length, outside diameter, and center opening, and note the top and bottom fittings.
Can I run my hot tub without a filter?
No. Running the spa without a filter lets debris reach the pump and heater and leaves the water unfiltered. Keep a clean spare to swap in while the other cartridge soaks or dries.
Can I use a pressure washer or dishwasher to clean a hot tub filter?
No. High pressure can tear the fibers, and dishwasher heat can warp the end caps. Use a garden hose at moderate pressure and a spa filter cleaner.
Should I let my hot tub filter dry before reinstalling it?
It isn't required, but letting a cartridge dry completely between uses can help it last longer. Rotating two filters makes that easy.
Will a new filter fix cloudy hot tub water?
Only if the filter is the cause. Balance the water and shock it first. If the water clears and stays clear only after you install a new cartridge, the old filter was the problem.