How to Clean a Pool or Hot Tub Filter Cartridge: Complete Guide

A clean filter cartridge is one of the most important parts of keeping pool or hot tub water clear, maintaining proper water flow, and protecting your pump, heater, and circulation system.

Unfortunately, cartridge filters are often either cleaned too aggressively, not cleaned often enough, or cleaned with products that can actually shorten the life of the filter.

This guide explains when to clean a pool or spa filter cartridge, how to clean it correctly, when a deep cleaning is necessary, what not to use, and how to tell when the cartridge should simply be replaced.

Why Cleaning Your Filter Cartridge Matters

A cartridge filter works by forcing water through pleated filter media. Dirt, hair, oils, insects, pollen, body products, and other contaminants become trapped in and between those pleats.

As debris accumulates, water becomes more difficult to push through the cartridge. Eventually, this can result in:

• Reduced water flow
• Higher filter pressure
• Poor filtration
• Cloudy water
• Reduced jet performance in a hot tub
• Heater or flow-related errors
• Additional strain on the circulation pump
• Premature filter-cartridge damage

Regular cleaning removes this buildup before it becomes severe enough to restrict the filtration system.

How Often Should You Clean a Pool Filter Cartridge?

For swimming pools, one of the best indicators is the filter's pressure gauge.

When installing a clean or new cartridge, note the filter's normal clean starting pressure. The exact pressure varies from one pool system to another.

A commonly used cartridge-filter guideline is to clean the cartridge when filter pressure rises approximately 8 PSI above the clean starting pressure.

For example:

• Clean starting pressure: 10 PSI
• Cleaning point: approximately 18 PSI

Do not focus on whether your filter normally runs at 8, 10, 15, or 20 PSI. What matters is the increase above your particular system's clean starting pressure.

How Often Should You Clean a Hot Tub Filter?

Hot tub filters are different because they deal with a much smaller volume of warm water and a relatively high concentration of contaminants from bathers.

Body oils, perspiration, lotions, cosmetics, hair products, and other contaminants can accumulate quickly in spa filter media.

Rather than relying solely on filter pressure, establish a routine based on how frequently the hot tub is used.

As a practical starting point:

• Light use: Inspect and rinse approximately every 2–4 weeks.
• Moderate or frequent use: Inspect and rinse more frequently as needed.
• Heavy use: Filters may require cleaning weekly or even more frequently.
• Deep cleaning: Periodically use an appropriate cartridge-filter cleaner to remove oils and contaminants that rinsing alone cannot remove.

Always follow the spa and filter manufacturer's specific maintenance recommendations when available.

What You Need to Clean a Filter Cartridge

For routine cleaning, you usually need very little:

• A garden hose
• A straight-stream or cartridge-cleaning hose nozzle
• A clean work area
• A commercial pool or spa cartridge-filter cleaner for periodic deep cleaning
• A clean plastic container large enough to soak the cartridge when deep cleaning

You do not need a pressure washer, wire brush, stiff scrub brush, or abrasive cleaning tool.

Step 1: Turn Off the Pump and Filter System

Before opening a filter housing, shut off the circulation pump and any related equipment according to the manufacturer's instructions.

Never attempt to open a pressurized filter tank.

If your filter has an air-relief valve, follow the manufacturer's procedure for relieving internal pressure before removing the lid, clamp, or cartridge.

Step 2: Remove the Cartridge

Carefully remove the cartridge from the filter housing according to the manufacturer's instructions.

Take a moment to inspect the cartridge before cleaning it.

Look for:

• Torn or damaged filter media
• Cracked end caps
• A collapsed center core
• Loose or missing support bands
• Flattened or badly distorted pleats
• Heavy discoloration
• Mineral deposits

If the cartridge is physically damaged, cleaning may not solve the problem and replacement may be necessary.

Step 3: Rinse From the Top Down

Use a garden hose with a straight or moderately concentrated stream of water.

Beginning at the top of the cartridge, work your way downward while directing water between the pleats.

A roughly 45-degree angle can help push debris out from between the folds rather than forcing it deeper into the media.

Work methodically around the entire cartridge. Separate the pleats gently with your fingers when necessary so water can reach the material trapped deeper between them.

Take Your Time Between the Pleats

The visible outside surface isn't the only part that needs cleaning.

Much of the dirt in a cartridge becomes trapped deep between the pleats. Rotate the cartridge as you work and make sure every section receives attention.

Continue rinsing until the water leaving the cartridge is clear and you no longer see significant debris between the pleats.

Do Not Use a Pressure Washer

A pressure washer may make the cartridge look clean quickly, but the concentrated water pressure can damage the filter media and reduce its ability to filter properly.

A normal garden hose provides plenty of pressure for routine cartridge cleaning.

Step 4: Deep-Clean Oils and Organic Contaminants

Rinsing removes loose dirt and debris, but it does not always remove oils.

This is particularly important with hot tub filters and pool filters exposed to:

• Body oils
• Perspiration
• Sunscreen
• Lotions
• Cosmetics
• Hair-care products
• Other organic contaminants

Periodically soak the cartridge using a commercial cleaner specifically designed for pool and spa filter cartridges.

Follow the cleaner manufacturer's mixing ratio and soaking instructions. Some products require only a short treatment, while others are designed for several hours or overnight soaking.

Make sure the filter is completely immersed when the product instructions call for soaking.

Step 5: Rinse Thoroughly After Deep Cleaning

After soaking, thoroughly rinse the cartridge with clean water.

Pay particular attention to the spaces between the pleats. Cleaning solution left behind in the cartridge can cause foaming or affect pool and spa water chemistry when the filter is returned to service.

Continue rinsing until the cartridge is free of cleaner and residue.

What About Calcium and Mineral Scale?

White, gray, or crusty deposits on the filter media may indicate calcium or other mineral buildup rather than ordinary dirt.

Mineral scale can be more difficult to remove because it becomes attached to the filter media.

Before treating mineral deposits, the cartridge must first be thoroughly cleaned of oils and organic contaminants.

Never acid-clean an oily cartridge. Acid can react with contaminants in the media and permanently restrict the filter.

Because acids can damage cartridge materials and create significant chemical-handling hazards, we recommend using a commercially formulated cartridge cleaner designed to address mineral deposits or following the filter manufacturer's specific cleaning procedure rather than automatically using a homemade muriatic-acid solution.

What If You Use BAQUACIL?

Filters used with a BAQUACIL® water-care system require additional attention because contaminants associated with biguanide-based systems may not respond to ordinary cartridge-cleaning procedures in the same way.

BAQUACIL currently recommends chemically cleaning cartridge filters with an appropriate BAQUACIL filter-cleaning product according to its current water-care instructions.

If your pool uses BAQUACIL or another specialized sanitizer system, follow the water-treatment manufacturer's filter-cleaning procedure rather than automatically using a generic cleaning method.

Should You Use Dishwasher Detergent or TSP?

Older cartridge-cleaning instructions sometimes recommend household dishwasher detergent or trisodium phosphate (TSP) solutions.

While some filter manufacturers have historically published these methods, we prefer a commercial pool and spa cartridge-filter cleaner for most homeowners.

A purpose-made cartridge cleaner provides clearer mixing and usage instructions and reduces the risk of using household products containing additives, fragrances, surfactants, or other ingredients that were never intended for pool or spa filtration systems.

Should You Use Bleach on a Filter Cartridge?

Do not automatically soak a cartridge in concentrated chlorine or household bleach.

Strong oxidizers can damage some filter materials and will not effectively remove the body oils and grease responsible for many clogged cartridges.

If disinfection is specifically required, follow the cartridge manufacturer's recommendations and the instructions for an appropriate pool or spa filter-cleaning product.

Should You Use Muriatic Acid?

Acid cleaning should be considered a specialized treatment for actual mineral buildup—not a routine filter-cleaning step.

Improper acid cleaning is one of the easiest ways to permanently damage cartridge media.

If acid treatment is specifically recommended by the filter manufacturer:

• Remove oils and organic contaminants first.
• Rinse the cartridge completely.
• Follow the manufacturer's exact dilution and safety instructions.
• Wear appropriate personal protective equipment.
• Never mix acid with chlorine or other pool chemicals.

For most homeowners, using a purpose-made cartridge cleaner intended for mineral deposits is the safer and simpler approach.

Step 6: Inspect the Cartridge Again

Once the cartridge is clean, inspect it before reinstalling it.

Look closely for:

• Tears or holes in the pleated media
• Cracks in either end cap
• A damaged or collapsed internal core
• Severely flattened pleats
• Loose or deteriorated support bands
• Permanent discoloration or buildup that did not respond to cleaning

A damaged cartridge should generally be replaced rather than returned to service.

Step 7: Clean the Filter Housing

Before reinstalling the cartridge, remove loose debris from the filter housing.

Inspect accessible components such as:

• Filter-tank O-rings
• Sealing surfaces
• Air-relief components
• Drain plugs
• Internal manifolds or cartridge supports

Replace damaged seals or components as necessary and follow the filter manufacturer's instructions for any lubricant used on O-rings.

Step 8: Reinstall the Cartridge and Restart the System

Install the clean cartridge in the correct position and reassemble the filter housing according to the manufacturer's instructions.

Make sure clamps, locking rings, lids, and other closures are properly positioned before restarting the pump.

Follow the manufacturer's procedure for bleeding trapped air from the filter.

Once the system is operating normally, note the pressure gauge reading. This becomes your new clean starting pressure.

When Should a Filter Cartridge Be Replaced?

A cartridge doesn't necessarily need replacement simply because it looks dirty. Proper cleaning can restore filtration performance many times.

However, filter cartridges eventually wear out.

Common signs that replacement is necessary include:

• The time between cleanings becomes much shorter than it used to be.
• Water flow remains poor after the cartridge has been thoroughly cleaned.
• Filter pressure remains unusually high after cleaning.
• The filter media is torn or has developed holes.
• The center core has collapsed.
• An end cap is cracked or damaged.
• The pleats are severely flattened, brittle, or deteriorated.
• The cartridge remains heavily clogged even after proper deep cleaning.

If your filter used to operate for several weeks between cleanings and now reaches its cleaning pressure again after only a few days, the cartridge may be nearing the end of its useful life.

How Long Should a Cartridge Filter Last?

There is no universal replacement interval for every pool or hot tub filter cartridge.

Cartridge life depends on:

• Pool or spa usage
• Filter size
• Water chemistry
• How frequently the cartridge is cleaned
• How the cartridge is cleaned
• Bather load
• Exposure to oils and lotions
• Environmental debris
• Circulation-system condition

A properly maintained cartridge can last considerably longer than one that is repeatedly allowed to become severely clogged or is damaged by aggressive cleaning.

The condition and performance of the cartridge are better indicators than its age alone.

Can You Clean a Filter Cartridge Too Often?

Yes.

A cartridge does not need to be removed and aggressively cleaned every time you see a small amount of dirt.

As a cartridge captures very fine particles, the accumulated material can actually contribute to filtration efficiency. Cleaning too frequently creates unnecessary wear without necessarily improving filtration.

For pool systems, use the pressure increase above clean starting pressure as your primary guide. For spas, use an appropriate routine based on usage, water flow, and filter condition.

Can You Put DE Powder in a Cartridge Filter?

Standard diatomaceous earth (DE) powder should generally not be added to a conventional cartridge filter unless the filter manufacturer specifically approves it.

DE particles can become embedded in cartridge media and may shorten filter life or create flow restriction.

If you are considering any filter-aid product, verify that it is specifically approved for your cartridge filter.

Should You Have a Second Set of Filter Cartridges?

For many pool and spa owners, keeping a second set of cartridges can be extremely convenient.

Instead of rushing through a cleaning because the pool or spa needs to go back into service, you can install the clean spare set and properly deep-clean the dirty cartridges separately.

Alternating two sets can also make it easier to give each cartridge a thorough cleaning and inspection.

Pool & Spa Cartridge Cleaning Checklist

• Turn off the circulation system.
• Relieve filter pressure according to the manufacturer's instructions.
• Remove the cartridge.
• Inspect for physical damage.
• Rinse from top to bottom with a garden hose.
• Clean carefully between every pleat.
• Deep-clean periodically with a cartridge-filter cleaner.
• Rinse all cleaning solution from the cartridge.
• Treat mineral buildup only when necessary and according to manufacturer instructions.
• Inspect the cartridge again after cleaning.
• Clean and inspect the filter housing.
• Reinstall the cartridge correctly.
• Bleed air from the system as directed by the manufacturer.
• Record the new clean starting pressure.

Five Things That Can Ruin a Filter Cartridge

• Pressure washing: High-pressure water can damage the pleated media.
• Stiff brushes: Aggressive scrubbing can tear or weaken the filter material.
• Improper acid cleaning: Acid used before oils are removed can permanently clog the media.
• Running excessively dirty: Severe restriction can damage end caps or collapse the cartridge core.
• Poor water chemistry: Scale and chemical damage can dramatically shorten cartridge life.

A Clean Filter Protects More Than Your Water

Keeping your cartridge filter clean isn't just about making the water look better.

Proper filtration and water flow help the entire circulation system operate correctly. A severely clogged cartridge can reduce flow through the pump, heater, and other equipment and may contribute to flow-related operating problems.

A few minutes of regular filter maintenance can help improve water clarity, maintain circulation, reduce unnecessary equipment strain, and extend the useful life of the cartridge itself.

Filter-cleaning procedures vary by filter manufacturer and model. Always follow the filter manufacturer's operating, pressure-relief, cleaning, chemical-handling, and reassembly instructions when they differ from general recommendations in this guide.