How often to clean a hot tub filter

For most hot tubs, the answer to how often to clean hot tub filter cartridges is this: rinse them every week or two, give them a chemical deep clean every one to three months, and replace them every 12 to 24 months. Heavier use moves every step sooner, and lighter use gives you a little more time.

Those numbers are a starting point, not a rule. This guide matches the schedule to how much your tub is actually used, lists the signs that a filter needs attention before its next date, and explains when cleaning stops being worth it. For the step-by-step method itself, see our guide to cleaning a hot tub filter properly.

Why does filter cleaning frequency matter?

The filter catches hair, skin cells, body oils, cosmetics, sun cream and garden debris. As it loads up, the gaps between the fibres close, water flow drops, and the pump and heater have to work harder.

Reduced flow also means less water passes through the filter each hour, so the water turns cloudy faster and your chlorine or bromine is used up more quickly. Many tubs will show a flow error and stop heating to protect themselves.

A filter that only ever gets rinsed loses filtering efficiency steadily, because oils and scale build up deep in the fabric where a hose cannot reach. Within about three months it can be noticeably less effective, so do not rely on rinsing alone.

Rinsing often still does an important job. It removes light debris before it has time to compact into the filter media, so the dirt that remains stays near the surface. That keeps the later spray and soak cleans easier and more effective.

A restricted filter also costs you money. The pump has to work harder to push water through it, which raises energy use, so a clogged filter makes the tub more expensive to run as well as harder on the equipment. The extra load builds gradually as the filter clogs, which is why it is easy to miss on a monthly bill.

How much extra energy a clogged filter costs depends on the pump and how badly the filter is blocked. Figures quoted in the industry suggest a heavily restricted filter can raise pump energy use by as much as about 30%. Treat that as an upper estimate rather than a typical figure, but it shows a clogged cartridge is a real running cost, not just a maintenance job.

There is a health side too. When the filter is clogged, less water is cleaned each hour and bacteria can multiply in the water you are sitting in. A dirty filter is a hygiene risk as well as an equipment one.

Cleaning too often is a smaller problem, but it is still real. Every chemical soak and every rinse wears the fabric a little, so there is no benefit in deep cleaning a filter that only needs a rinse.

How often to clean hot tub filter cartridges: a schedule by usage

Filter care splits into three jobs. A rinse removes loose debris. A chemical deep clean dissolves the oils and minerals that a rinse leaves behind. Replacement covers the point where the fabric is simply worn out.

How often you do each job depends mainly on bather load: how many people use the tub, how often, and for how long. The table below gives typical intervals. Manufacturers differ, so check your manual and use whichever interval is shorter.

Be honest when you count your use. Two people using the tub every evening is heavy use, even if it feels like a quiet routine. A weekend party with several guests can load a filter as much as a normal fortnight does.

The schedule is the same whether your tub has a top-load or a side-load filter housing. The cleaning is identical, and the only difference is how you reach the cartridge and refit it, which your manual will show.

Light use

If you use the tub once or twice a week with one or two people, a rinse every two weeks usually keeps on top of things. A deep clean every three to four months fits neatly with draining and refilling the tub.

Regular use

Three to five sessions a week, or a couple who use the tub most evenings, calls for a weekly rinse. Plan a deep clean every two to three months and expect a filter to last around 12 to 18 months.

Heavy use

Daily use by a family, frequent guests or a holiday let needs a rinse twice a week and a deep clean roughly once a month. Many owners in this group keep two sets of filters, so a clean, dry set is always ready.

A simple rule of thumb also helps. If the tub gets more than three sessions a week, or regularly has three or more bathers at once, rinse every three to four days and deep clean monthly rather than quarterly. If you sit between two rows of the table, follow the stricter one.

Setting up a two-filter rotation

1. Fit filter A and write the date on its end cap with a permanent marker.
2. When filter A is due a rinse, switch the tub off and swap in clean, dry filter B.
3. Rinse filter A and leave it to dry somewhere shaded and airy.
4. When a deep clean is due, soak the filter you have just removed, rinse it thoroughly and let it dry completely.
5. Keep swapping on each rinse date, so each filter gets a full rest and a deep clean in turn.
6. Replace each filter when it reaches the end of its life, using the dates on the end caps to keep track.

If your tub takes two filters at once, clean them in turn so one is always fitted. Never remove both cartridges at the same time, because the tub then has nothing protecting the pump and heater.

Before you lift a filter out, switch the tub off at the isolator. Removing a filter while the pump is running can pull debris straight into the plumbing, the pump and the heater.

Should inflatable hot tubs follow a different schedule?

Yes. Inflatable and many small portable tubs use compact cartridges with far less pleated area than a full-size spa filter. They clog much faster, so rinsing every one to three days during regular use is common guidance.

These cartridges are inexpensive, and many manufacturers treat them as consumables that should be replaced every few weeks rather than deep cleaned. Your manual will give the interval for your model. It is worth following, because a clogged cartridge in an inflatable tub can quickly trigger flow errors.

Inflatable cartridges typically cost only about £3 to £8 each. At that price, fitting a new one is often more practical than spending time on long cleaning routines.

The media in these cartridges is thinner than in a full-size filter and can break down faster with chemical soaks. Rinse thoroughly after each use, and only use a spray cleaner if your model's manual allows it.

Keep a few spares and fit a fresh one when the old one stays grey after a rinse. If the tub sits unused for several days, rinse the cartridge before the next session rather than leaving debris to dry inside it.

What are the signs a hot tub filter needs cleaning early?

A schedule is a reminder, not a guarantee. Clean the filter ahead of time if you notice any of the following:

• Weaker jets, or a gentler flow from the return fittings than usual
• A flow, pressure or heating error on the control panel (codes vary by brand)
• Water that looks dull or cloudy even though your test results are in range
• Foam that keeps coming back after you treat it
• Water that turns cloudy or foamy and does not clear within 24 hours of chemical treatment, or looks dirty again soon after
• Sanitiser that runs out faster than it normally does
• Pleats that look grey, brown or greasy rather than white or cream
• Visible slime on the pleats that will not rinse off
• A persistent chemical smell even though your sanitiser level is correct
• A white, crusty or gritty coating on the pleats, which is scale from hard water
• Little or no light showing through the pleats when you hold the cartridge up to a bright light, which means it is badly restricted
• A pressure gauge (fitted to some tubs) reading noticeably higher than it did with a clean filter

When any of these early-warning signs appears, such as cloudy or foamy water, slime on the pleats, a chemical smell or weak jets, give the filter at least a spray-cleaner treatment straight away. Do not wait for its next scheduled date. If the problem is still there after the spray clean, follow up with a full overnight soak.

Some events also call for an early rinse: a party or busy weekend, a storm that blows leaves into the tub, the height of pollen season, or shocking the water after a cloudy spell. Shock breaks contaminants down, and the filter then catches what is left.

If a clean filter does not bring back normal flow, the problem may lie elsewhere. An airlock, a blocked suction cover or a failing pump can cause the same symptoms, so check those before blaming the filter.

In the same way, if the water stays cloudy with a freshly cleaned or new filter and balanced chemistry, the filter is probably not the cause. Look at the sanitiser system or the fill water instead, and test the water thoroughly or ask a pool and spa supplier for a professional water analysis rather than cleaning the filter again.

Rinse, spray or soak: what does each level of cleaning do?

Each level of cleaning removes a different kind of dirt. That is why a frequent rinse cannot replace an occasional soak, and why a soak alone is not enough between rinses.

Do not expect a tap or hose rinse alone to leave a filter looking clean. Oils and scale embed deep in the pleats where water pressure cannot reach, so choose the level of cleaning to match how dirty the filter actually is.

The three levels also take very different amounts of time. A routine hose rinse takes about 5 minutes and a spray-cleaner session about 20 minutes, but a deep soak needs 12 to 24 hours. Plan the soak ahead, for example by starting it in the evening or fitting a spare filter while it soaks.

What to have ready

Gather everything before you open the filter housing. If you have to hunt for kit halfway through, the cartridge sits exposed to blown debris and can start to dry out unevenly.

• A garden hose with an adjustable nozzle that has a fan or shower setting
• A bucket or tub large enough to submerge the whole cartridge
• A filter cleaner, either spray-on or soak, suitable for your sanitiser
• Rubber gloves
• A clean surface to rest the filter on

Taking the filter out

1. Switch the tub off at the isolator.
2. Open the filter housing and remove any lid or skimmer basket covering the cartridge.
3. On many models, twist the filter anticlockwise to release it. On others, unclip the housing cover first.
4. Lift the filter out and put it on a clean surface, such as a patio slab or an upturned bucket lid.

The routine rinse

Use a garden hose with a fan or shower setting. Work from the top of each pleat downwards, at an angle, so dirt is pushed out rather than driven deeper. Never use a pressure washer, because it can tear the fibres and fray the pleats.

1. Hold the hose at roughly 45 degrees to the pleats.
2. Work from the top of each pleat down to the bottom.
3. Rotate the cartridge all the way round so no section between the folds is missed.
4. Rinse the central core and both end caps, because debris works its way down into them.
5. Keep going until the water running off the filter looks clear.

A hose attachment made for filter cleaning, which sends angled jets between the pleats, can do a more thorough job than a plain hose nozzle. It is worth considering if you rinse often.

If the cartridge still looks grey, brown or discoloured after a routine rinse, rinsing it again will not help. Move up to a spray-cleaner treatment, which dissolves the oils that plain water leaves in the pleats.

The spray-on cleaner

A spray-on filter cleaner, left for the time on its label and then rinsed off, lifts oils and lotions that plain water leaves behind. It sits between a rinse and a soak, and suits regular or heavy users who want to stretch the time between soaks.

A spray cleaner also breaks down light biofilm, the thin slimy layer that bacteria form, in the outer layer of the filter media. Its short contact time means it cannot reach far into the fabric, so deeper biofilm needs a soak.

1. Put on rubber gloves before handling the cleaner.
2. Give the filter a light hose rinse to remove loose debris.
3. Spray the cleaner evenly over the pleats, turning the filter as you go.
4. Lay the filter flat while the cleaner works for its dwell time, typically 5 to 15 minutes. Follow the label.
5. Rinse thoroughly until the water runs completely clear.

If heavy discolouration remains after a spray clean, do not spray again. Move up to a full soak, which reaches dirt that a spray cannot.

The deep soak

A soak in a dedicated filter cleaning solution, usually overnight, dissolves the oils that bind dirt into the fabric. In hard water areas, choose a product that also removes scale, or descale separately. Our guide to choosing a hot tub filter cleaner explains the difference between degreasers, descalers and combined products.

Because the filter sits in the solution for hours, an overnight soak reaches deeper biofilm and calcium deposits inside the media that a spray's short contact time cannot. That is why a soak can restore flow when spraying no longer does.

Before you buy any filter cleaner, check the label says it is compatible with your sanitising system, whether that is chlorine, bromine, ozone or a mineral system. For cartridges, prefer a product whose stated use is a soak followed by a rinse, and follow its directions rather than improvising.

Always rinse thoroughly after a soak, because leftover cleaner causes foam. Then let the filter dry completely before refitting or storing it. Drying helps the fibres recover and lets any loosened scale flake away.

1. Put on rubber gloves.
2. Rinse the filter to remove loose debris.
3. Choose a bucket or tub big enough to submerge the filter completely.
4. Fill it with cold or lukewarm water. Hot water can warp the core.
5. Add the cleaner, following the product's dilution instructions exactly.
6. Lower the filter in. If it floats, weigh it down, for example with a full water bottle, so it stays fully under the surface.
7. Leave it for the soak time below, or the time on the product label.
8. Rinse with continuous hosing for around 2 to 3 minutes, until the water runs completely clear.
9. Let the filter dry before refitting it.

As a guide to soak times:

• Lightly to moderately soiled filters: at least 12 hours
• Heavily discoloured or clogged filters: 24 hours
• Filters not cleaned in six months or more: up to 48 hours, if 24 hours has not restored them

After refitting the filter

1. Refit the filter and close the housing.
2. Switch the tub back on.
3. Run it on circulation for about 15 minutes.
4. Test the water chemistry and adjust it if needed before anyone gets in.

Which household cleaners are safe for a hot tub filter?

Most household products either do too little or cause damage. Here is how the common ones compare.

• White vinegar: mildly acidic and can loosen light scale, but it does not remove oils. Advice on long soaks differs, and some manufacturers warn that acid can weaken the fabric or end caps. If you use it, dilute it, keep the soak short, rinse well and check your manual first.
• Bicarbonate of soda: gentle and unlikely to harm the filter, but it does little against greasy build-up or scale. It can also leave an alkaline residue on the pleats that slightly shifts your water chemistry if it is not rinsed off thoroughly.
• Oxygen-based laundry boosters: some owners use them for soaks, but many contain fragrances or additives you would not want in your water. A product made for spa filters is the safer choice.
• Bleach: avoid it. Bleach can break down the polyester fibres and weaken the glue that holds the end caps, which shortens the filter's life. It can also leave chlorine residue that makes sanitiser readings spike unpredictably, and it should not be used in a poorly ventilated space.
• Washing-up liquid: avoid it. It is hard to rinse out of the pleats and leaves a residue that causes heavy foam. Residue from washing-up liquid or any soap not made for spas can also disrupt the water chemistry, take days and several water changes to clear, and may damage pump seals over time.

Look at the filter before choosing a cleaner. A chalky white coating suggests scale, which vinegar can help with. A brown or greasy filter is loaded with oils, and vinegar does nothing for those, so it needs a dedicated cartridge cleaner.

If your manual allows vinegar, this is a typical scale treatment:

1. Rinse the filter to remove loose debris.
2. Mix white vinegar and water in roughly equal parts, enough to cover the filter.
3. Soak the filter for 1 to 2 hours.
4. Rinse thoroughly, because leftover vinegar lowers the pH of your tub water.
5. On heavily scaled filters, follow it with a chemical filter soak, using the vinegar as a pre-treatment.

Never mix vinegar with bleach or any chlorine product, and never use them on a filter one after the other without a thorough rinse in between. The combination releases toxic chlorine gas.

Plain sodium percarbonate, the active ingredient in many oxygen laundry boosters, can work as an interim soak for organic staining. Use about 1 to 2 tablespoons per 4.5 litres (1 UK gallon) of water, soak for 30 to 60 minutes, then rinse very well. Choose one without fragrance, and treat it as a stopgap, not a substitute for a proper filter cleaner.

Can you use a dishwasher or washing machine?

No. The heat inside a dishwasher can warp the end caps and the plastic core, and detergent residue causes foam. A washing machine spins and twists the cartridge, which can crush the core and crease the pleats permanently. The time saved is not worth a damaged filter.

Dishwashers typically run at around 55-75°C (131-167°F), which is hotter than filter cartridges are made to handle. The adhesives that bond the media can soften, so the core warps, the end caps loosen and the pleats separate. Detergent left in the pleats can also force a full drain and refill.

A washing machine can crack end caps and permanently deform pleats even on a delicate or cold cycle. This damage cannot be reversed, so the filter will need replacing.

When should you replace a hot tub filter rather than clean it?

Even with good care, the fabric wears out. Most cartridges last 12 to 24 months, and some manufacturers describe filter life by the number of deep cleans instead. Replace the filter if you see any of these signs:

• Torn, split or frayed pleats
• Pleats that have gone soft, flattened or stuck together
• Pleats collapsing inwards towards the core
• Cracked or loose end caps, or a crushed or warped core
• Discolouration or scale that a deep soak no longer removes
• A musty or unpleasant smell after cleaning
• A chemical odour that persists after a full soak and a thorough rinse
• Flow that drops again within a few days of a full clean
• A filter more than two years old that no longer performs well, however carefully it has been cleaned

A worn filter lets fine particles straight through, which leaves the water hazy and puts extra strain on your sanitiser. You can read more about when to replace a hot tub filter. If you need a new one, our guide on how to choose the right hot tub filter covers sizes, fittings and materials.

A replacement cartridge for most home hot tubs costs roughly £15 to £50. That is far less than a pump repair caused by running a tub on a degraded filter, so replacing on time is the cheaper choice.

How does filter care fit into the rest of your routine?

The filter and your water chemistry depend on each other. Balanced water filters better, and a clean filter helps your sanitiser keep the water clear. These are the widely accepted target ranges:

• Free chlorine: 3-5 ppm, or bromine: 3-5 ppm
• pH: 7.2-7.6
• Total alkalinity: 80-120 ppm
• Calcium hardness: 150-250 ppm

A dirty filter and poor chemistry also feed each other. Reduced circulation spreads sanitiser unevenly, bacteria and biofilm grow faster in the weak spots, and that extra growth clogs the filter faster still.

Test the water at least twice a week. Filter condition affects how stable your readings are, so readings that drift between tests are often an early hint that the filter needs attention.

High pH and high calcium hardness speed up scale on the pleats, so if your filter crusts over quickly, test those two first. Low sanitiser leaves more organic material in the water for the filter to trap, which means more frequent rinsing.

A neglected filter can also harbour bacteria, including Legionella in poorly maintained systems. The Health and Safety Executive's guidance on Legionella includes hot tubs and explains why regular cleaning and disinfection matter. If anyone develops a rash or flu-like symptoms after using the tub, stop using it and speak to a pharmacist or GP.

It helps to see filter care alongside everything else the tub needs. Our hot tub maintenance checklist puts rinsing and soaking next to water testing, draining and cover care, so nothing slips.

Does the tennis ball trick work?

Floating a tennis ball in the tub is meant to soak up surface oils. It may absorb a small amount, but it does not replace cleaning the filter or keeping your chemistry in range. If you try it, change the ball often and keep it out of the filter housing.

Use a new, unused ball, not one from the garden or the dog's toy box. Replace it every 2 to 4 weeks, or sooner if it looks discoloured. Think of it as a way to reduce the oil reaching the filter, not as a cleaning step.

What mistakes shorten a filter's life?

• Using a pressure washer, or holding a jet nozzle close to the pleats
• Scrubbing the pleats with a stiff brush
• Cleaning with bleach, washing-up liquid or a dishwasher
• Refitting a filter that still holds cleaning solution
• Refitting a filter that is still soaking wet, which can dilute the water chemistry and temporarily throw off sanitiser readings
• Waiting for an error code before cleaning
• Skipping the periodic deep soak, because rinsing and spraying only manage surface dirt while embedded oils and scale build up over months
• Running the tub without a filter fitted, which lets debris reach the pump and heater
• Running the pump while the filter is out, which can draw air and debris into the pump, a repair that costs far more than a new filter
• Storing a damp filter in a sealed bag, which encourages mould

Most of these mistakes come from trying to save time. A gentle rinse on schedule and a full dry afterwards take only a few minutes, and they add months to a filter's working life.

A simple filter schedule to remember

Rinse every week or two, deep clean every one to three months, and replace every one to two years, then adjust for how hard your tub works. Heavy use, hard water and inflatable tubs all shorten those intervals.

Watch for weaker jets, cloudy water and greying pleats, and act early rather than waiting for an error code. Gentle cleaning, the right products and a full dry between uses will get the most life out of every filter.

Frequently asked questions

Can I clean the filter with the pump running?

No. Switch the tub off at the isolator, and at the breaker or control panel too, before you open the filter housing. With the pump running, debris can be sucked into the plumbing as soon as the filter is lifted. Some tubs have a filter or maintenance mode that pauses the pumps, but switching off at the isolator is the safest habit, and the tub should never run without a filter fitted.

How do you unclog a badly blocked filter?

A rinse will not clear a heavily blocked filter. It needs a full overnight soak in a dedicated filter cleaner, followed by a thorough rinse. If the pleats are crusted with scale, a short vinegar soak beforehand can help, as long as you rinse well between the two. If flow is still poor after the soak and a full dry, the filter has reached the end of its life and should be replaced.

Should I keep a spare filter?

A spare is very useful, especially with regular or heavy use. You can fit a clean, dry filter straight away instead of waiting for a soaked one to dry, so the tub is never out of action. Rotating two filters also lets each one dry fully between uses, which helps the fabric recover and can extend the life of both.

Do I need to rinse a new filter before fitting it?

Many manufacturers recommend a quick rinse with a garden hose before first use. It removes loose fibres and dust from manufacturing or packaging that could otherwise cloud the water. Some filters carry a specific instruction, so check the packaging. There is no need to soak a new filter in cleaner before fitting it.

How long should a filter dry after cleaning?

Drying times vary with the weather, but a full day in a shaded, airy spot is a sensible minimum, and longer in cold or damp conditions. Keep it out of strong direct sun for long periods, which can weaken the fabric. It should feel dry right through the pleats before storage. Never refit a dripping filter: if you have no spare, let it drain and air-dry at least briefly first.

Should I clean the filter when I drain the tub?

Yes, draining and refilling is a good time for a deep clean. Fresh water and a fresh filter start together, and you avoid putting a dirty filter into clean water. If your filter is close to the end of its life, a refill is also a natural point to fit a new one.

Why does my filter get dirty so quickly?

The usual causes are a high bather load, lotions or sun cream on skin, low sanitiser levels, or hard water that leaves scale. Showering before getting in removes much of the oil and product that would otherwise end up in the pleats. If the filter still clogs fast, test your water and check that the cover fits well, since a loose cover lets in leaves and dust.