How to Clean Hot Tub Filters

The water’s gone cloudy, the jets seem weaker than usual, and there’s a vaguely swampy smell that definitely wasn’t there last week. Before you panic and dump every chemical in the shed into the tub, check the filters. Dirty filters are the single most common cause of hot tub water problems — and they’re the easiest to fix. I’ve owned two hot tubs over the past five years, and learning to clean the filters properly was the turning point between frustrating water chemistry battles and a tub that just works.

In This Article

• Why Hot Tub Filters Matter More Than You Think
• Types of Hot Tub Filters
• How Often to Clean Your Filters
• The Quick Rinse (Weekly)
• The Deep Clean (Monthly)
• The Chemical Soak (Quarterly)
• When to Replace Filters Entirely
• Common Filter Cleaning Mistakes
• Choosing Replacement Filters
• Filter Cleaning Products Compared
• Troubleshooting Filter Problems
• Frequently Asked Questions

Why Hot Tub Filters Matter More Than You Think

Your hot tub filter is the first line of defence between you and a bathtub of body oils, dead skin cells, sunscreen residue, and whatever the kids brought in on their feet. The filter traps particles as small as 20-30 microns (about half the width of a human hair) and keeps the water clear enough to see the bottom.

When the filter clogs, three things happen fast:

• Water flow drops — the pump can’t push water through a blocked filter, so jet pressure weakens and the heater can’t circulate enough water to maintain temperature
• Sanitiser efficiency drops — chlorine or bromine needs flowing water to distribute evenly. Stagnant zones become breeding grounds for bacteria
• The pump works harder — a clogged filter increases back-pressure, which strains the pump motor and shortens its lifespan. Pump replacements cost £200-500.

According to the Chartered Institute of Building Services Engineers (CIBSE), maintaining proper water circulation is essential for both hygiene and equipment longevity in any heated water system.

The Numbers

A well-maintained filter in a 4-person hot tub traps about 5-10 grams of organic material per week. That’s skin cells, body oils, hair, cosmetics, and environmental debris. Over a month without cleaning, that adds up to 30-40 grams of organic sludge packed into the filter pleats — enough to reduce water flow by 30-50%.

Types of Hot Tub Filters

Pleated Cartridge Filters (Most Common)

The vast majority of UK hot tubs use pleated polyester cartridge filters. They look like a white cylinder with accordion-like folds. The pleats increase surface area — a typical filter has about 3-5 square metres of filtration area packed into a cylinder 25 cm long.

• Pros: Cheap to replace (£15-40 each), easy to remove and clean, effective at trapping particles
• Cons: Need regular cleaning, degrade over time, can’t be cleaned forever
• Lifespan: 12-18 months with proper care

Ceramic Disc Filters

Less common in the UK, these use stacked ceramic discs instead of polyester. Found in some Jacuzzi and premium brands.

• Pros: Last longer (2-3 years), finer filtration
• Cons: More expensive to replace (£50-80), harder to find in the UK

Microban/Antimicrobial Filters

Some cartridge filters include Microban antimicrobial treatment that inhibits bacterial growth within the filter media itself.

• Pros: Slower bacteria buildup between cleanings, slightly longer intervals between deep cleans
• Cons: 20-30% more expensive than standard cartridges, the antimicrobial effect diminishes over time
• Worth it? For heavily used tubs (daily, multiple users), yes. For occasional use, standard filters are fine.

How Often to Clean Your Filters

Weekly: Quick Rinse

Remove the filter and hose it down. Takes 5 minutes. This removes the surface debris that accumulates from normal use.

Monthly: Deep Clean

Soak the filter in a dedicated cleaning solution for 8-24 hours. This dissolves the oils, lotions, and organic buildup that rinsing alone can’t reach.

Quarterly: Chemical Soak

A thorough chemical soak using a filter-specific cleaner designed to break down mineral scale and deep-seated organic contamination. This extends the filter’s usable life.

Annually: Replace

Even with perfect maintenance, filter cartridges degrade. The polyester fibres stretch, the pleats lose their shape, and filtration efficiency drops. Budget £15-40 per filter per year — a small price compared to the chemical chaos a failing filter causes.

Adjust for Usage

These intervals assume a 4-person tub used 3-4 times per week:

• Heavy use (daily, multiple people): Rinse twice weekly, deep clean fortnightly
• Light use (once a week, 1-2 people): Rinse fortnightly, deep clean monthly
• Party weekend: Rinse immediately after, deep clean within the week. We learned this the hard way — six adults in a hot tub on a Saturday night means the filter looks like it’s been through a swamp by Sunday morning.

The Quick Rinse (Weekly)

This is the maintenance task that takes the least time and has the biggest impact. If you do nothing else, do this.

What You Need

• A garden hose with a spray nozzle (a dedicated filter cleaning wand — about £12 from Amazon UK — makes this easier)
• 5 minutes

Step by Step

1. Turn off the hot tub at the isolator switch (never remove filters with the power on — the pump will run dry)
2. Remove the filter — usually a twist-and-pull or twist-and-lift motion. Check your manual if you’re unsure.
3. Starting at the top, work the hose spray between each pleat, angling the water downward
4. Rotate the filter as you go, ensuring every pleat gets flushed
5. Look at the water running off — it should start dirty brown/grey and finish running clear
6. Once the water runs clear from all pleats, replace the filter
7. Power the tub back on

Tips

• Use a dedicated filter cleaning wand that produces a fan-shaped spray — it gets between the pleats better than a standard nozzle
• Don’t use a pressure washer — the high pressure damages the filter fibres and opens up the pore structure, reducing filtration effectiveness
• Do this on a warm day if possible — it’s more pleasant, and the water runs off easier

The Deep Clean (Monthly)

Rinsing removes surface debris, but it doesn’t touch the oils, lotions, and cosmetics that soak into the filter fibres. For that, you need a chemical soak.

What You Need

• A bucket or bin large enough to submerge the filter(s) completely
• Hot tub filter cleaning solution (not household bleach — more on this below)
• 8-24 hours (overnight is perfect)

Step by Step

1. Remove the filters and rinse them first (do the weekly rinse to remove surface debris)
2. Fill the bucket with warm water (not hot — it degrades some cleaning solutions)
3. Add the filter cleaner according to the dosage on the bottle
4. Submerge the filter(s) completely — weigh them down if they float
5. Leave for 8-24 hours (overnight is the sweet spot)
6. Remove, rinse thoroughly with a hose until the water runs completely clear
7. Allow to air dry for an hour if possible (the open pores trap more debris when dry)
8. Reinstall

Having a Spare Set

The professional move is to keep two sets of filters. While one set soaks overnight, the spare set goes in the tub. This means your tub is never without filtration, and you always have clean filters ready. A spare set costs £30-80 depending on your tub — easily worth it. If you’re looking at your overall running costs, see our guide to hot tub energy ratings for how much your tub costs to run.

The Chemical Soak (Quarterly)

Every three months, a more intensive soak breaks down mineral scale (calcium buildup from hard water areas — much of south-east England) and deeply embedded organic contamination.

Dedicated Filter Cleaner vs DIY

Dedicated filter cleaners (AquaFinesse, Aqua Kristal, Happy Hot Tubs Filter Cleaner — about £10-15 per bottle from Amazon UK) are specifically formulated for hot tub filter media. They contain surfactants that break down oils and degreasers that dissolve sunscreen and cosmetic residue.

DIY alternatives:

• White vinegar soak (1:3 ratio with water): Effective at dissolving mineral scale but doesn’t remove oils well. Useful for hard water areas as an additional step, not a replacement.
• Dishwasher tablets: Sometimes recommended online. Don’t use them — the anti-foaming agents can transfer to your hot tub water and cause problems.
• Household bleach: A very dilute bleach soak (1 tablespoon per 5 litres) can sanitise a filter, but it doesn’t dissolve oils and can degrade the filter fibres with repeated use. Last resort only.

Our Recommendation

Use a dedicated filter cleaner for the quarterly soak. It costs about £10 per treatment and is formulated for the job. Combine with a vinegar presoak if you’re in a hard water area. The combination cleans both the organic and mineral contamination.

When to Replace Filters Entirely

No amount of cleaning makes a filter last forever. Replace your filters when:

• The pleats won’t return to their original shape after cleaning — they stay compressed or flattened
• The filter is discoloured and won’t come clean even after a chemical soak — persistent brown, green, or grey staining
• The fabric feels slimy even after cleaning — biofilm has penetrated the fibres
• Water clarity is poor despite correct chemical balance — the filter isn’t catching particles anymore
• It’s been 12-18 months since installation — even if it looks OK, the pore structure has degraded

How to Check Filter Condition

Hold the filter up to light after cleaning. You should see light coming evenly through the pleats. Dark patches indicate areas where contamination hasn’t been removed — these zones aren’t filtering properly.

For a guide to choosing the right hot tub in the first place, see our complete buyer’s guide.

Common Filter Cleaning Mistakes

Using a Pressure Washer

This is the most common mistake. Pressure washers blast the filter fibres apart at a microscopic level, widening the pores. The filter looks clean but passes particles it previously would have caught. Use a garden hose only.

Putting Filters in the Dishwasher

Don’t. The heat warps the plastic end caps, the detergent leaves residue that foams in the hot tub, and the mechanical action damages the pleats.

Not Rinsing After Chemical Soak

Leftover cleaning solution transferred to the hot tub creates foam, pH fluctuations, and can irritate skin. Rinse thoroughly — at least 3-4 minutes of continuous hose water running through every pleat.

Running the Tub Without Filters

Some people remove the filters to clean them and forget to turn off the tub. Running the pump without filters means debris goes straight into the plumbing, where it clogs jets and accumulates in the pipework. Always power off before removing filters.

Using Swimming Pool Filters

Hot tub filters and swimming pool filters are not interchangeable. Pool filters are designed for cold water, higher flow rates, and different chemical environments. Use the correct filter specified for your hot tub model. Check our guide to maintaining your hot tub chemicals for the complete water care picture.

Choosing Replacement Filters

OEM vs Aftermarket

• OEM (Original Equipment Manufacturer): Made by or for your hot tub brand. Guaranteed to fit. Typically £25-40 each.
• Aftermarket: Made by third-party manufacturers to match OEM dimensions. Usually £15-25 each. Quality varies — stick to reputable brands (Pleatco, Filbur, Darlly).
• Our experience: After testing both, the Darlly aftermarket filters performed identically to the Jacuzzi OEM filters in our tub at half the price. We’ve been using Darlly for two years now with no issues.

Finding the Right Size

Every hot tub model uses specific filter dimensions. You need to match:

• Outer diameter (typically 12-17 cm)
• Length (typically 20-35 cm)
• Inner diameter/thread type (fine thread, coarse thread, or open hole)

The easiest way: check your current filter’s part number (printed on the end cap), then search for that number online. Most UK hot tub suppliers have cross-reference tools.

Where to Buy in the UK

• Hot Tub Suppliers (hottubsuppliers.co.uk) — wide range, fast delivery
• Amazon UK — convenient, check seller reviews
• Your hot tub dealer — most expensive but guaranteed correct fit

Filter Cleaning Products Compared

AquaFinesse Filter Cleaner

• Price: About £15 per 950ml from Amazon UK
• Performance: Excellent at removing oils and organic buildup. One bottle lasts 4-5 cleans.
• Verdict: Our top pick for monthly and quarterly soaks

Happy Hot Tubs Filter Cleaner

• Price: About £10 per 500ml
• Performance: Good all-rounder. Slightly less effective on heavy oil contamination than AquaFinesse but works well for regular maintenance.
• Verdict: Good value for weekly-use tubs

Spa Marvel Filter Cleaner

• Price: About £12 per 950ml
• Performance: Enzyme-based cleaner. Slower acting (needs 24 hours minimum) but very thorough.
• Verdict: Best for quarterly deep cleans when you have time

White Vinegar (Household)

• Price: About £1 per litre from any supermarket
• Performance: Only effective against mineral scale. Does nothing for oils or organic contamination.
• Verdict: Use as an additional step in hard water areas, not as a primary cleaner

Troubleshooting Filter Problems

Water Still Cloudy After Filter Cleaning

If the water remains cloudy after cleaning the filters, the issue is likely chemical balance rather than filtration. Check pH (should be 7.2-7.6), sanitiser levels, and alkalinity. If chemicals are balanced and water is still cloudy, the filters may need replacing.

Filter Clogs Within Days of Cleaning

This usually means the water itself has a high contamination load. Common causes:

• A recent party or heavy use without adjusting chemicals
• Algae growth (typically from low sanitiser levels)
• Biofilm in the plumbing — cleaning the filters won’t help because the contamination is coming from the pipes

Pump Making Unusual Noise

A strained, whining pump motor often indicates restricted water flow from clogged filters. Clean the filters first. If the noise persists with clean filters, the pump itself may need servicing.

Filters Won’t Fit After Cleaning

Polyester can swell when soaked in certain cleaning solutions. Allow the filter to dry completely before reinstalling. If it still doesn’t fit, the plastic end caps may have warped — replace the filter.

Frequently Asked Questions

Can I use household bleach to clean hot tub filters? As a last resort, yes — use a very dilute solution (1 tablespoon of household bleach per 5 litres of water) for no more than 2 hours. Bleach sanitises but doesn’t dissolve oils or lotions, which are the main contaminants in hot tub filters. Repeated bleach soaks degrade the polyester fibres, shortening filter lifespan. Dedicated filter cleaners are more effective and safer for the filter material.

How many filters does a hot tub have? Most 4-6 person hot tubs have 1-2 main filters. Some premium models have up to 5 smaller filters distributed around the shell. Check your owner’s manual for the exact number and locations. All filters need the same cleaning schedule — don’t clean one and forget the others.

Do I need to clean new filters before first use? Yes. New filters often have manufacturing residue (a fine coating from the production process) that should be rinsed off before installation. Give new filters a thorough hose-down and, ideally, a brief soak in clean water for an hour before fitting them.

Can I put hot tub filters in the washing machine? No. The mechanical agitation damages the pleat structure, the detergent residue causes foaming in your hot tub, and the heat from a hot wash can warp the plastic end caps. Hand cleaning with a hose and occasional chemical soak is the only safe method.

Why does my filter turn green? A green filter typically means algae growth, which indicates your sanitiser (chlorine or bromine) levels have been too low. Clean the filter with a chemical soak, then address the root cause by testing and adjusting your sanitiser levels. Algae indicates a water chemistry problem, not just a filter problem — fixing the filter alone won’t prevent it returning.