A hot tub filter sits in water full of skin oil, lotion and hair product, so it's catching grease as much as dirt. That's why a hose alone never quite finishes the job.
I read the current owner's manuals from five spa makers, plus the care instructions from Unicel, Filbur and Pentair, to see what they actually tell owners. They agree on the big things. Clean it about once a month, use a degreaser, keep the power off while it's out, and don't run the tub without it.
Before you start
- Time
- 2 hr
- Difficulty
- Easy
- Cost
- A bottle of spa filter cleaner
Tools
- Garden hose with a nozzle
- Plastic bucket or tub
- Gloves and safety glasses for acid
Supplies
- Spa filter cleaner
- Muriatic acid, only if scaled
Key takeaways
- Every manual I read lands near once a month: every four weeks for Hot Spring and Caldera, monthly for Jacuzzi and Sundance, every 3 to 6 weeks for Bullfrog's X Series. More use means sooner.
- A hose moves debris, not oil. Hot Spring and Caldera put a degreaser soak into every cleaning, and Jacuzzi and Sundance call for one periodically.
- Power off before the filter comes out, and never run the tub without it. Bullfrog says the filter is part of what stops a body being held against the suction fitting.
- Acid comes last, if at all, and only after a degreaser. Unicel and Pentair use 1 part acid to 20 of water, and Bullfrog's manual says 1 to 10.
- Check what kind of filter you have first. Sundance's inner insert takes no cleaner at all, and Hot Spring's Tri-X is the only filter I found that a maker allows in a dishwasher.
How often to clean it
Every manual I read lands near once a month. None of them uses the pressure rule a pool filter does. Unicel's pool rule is a gauge reading 8 psi over the clean pressure, but for spas it says to set a routine based on how much the tub gets used.
| Clean it | Cleaner soak | Replace it | |
|---|---|---|---|
| Hot Spring | Every four weeks | Every cleaning | When discolored, or the rubber shows wear |
| Caldera | Every four weeks | Every cleaning | No interval given |
| Jacuzzi J-300 | Once a month | Periodically, overnight | About two years on average |
| Sundance 880 | Monthly | Periodically, outer filter only | Pleated filter 18 months, insert 6 months |
| Bullfrog X Series | Every 3 to 6 weeks | To remove lotions and oils | After multiple cleanings |
| Bullfrog A Series | Every 4 weeks, or replace | Not mentioned | At least every 12 to 16 weeks |
Those are starting points. Hot Spring and Caldera both say that more use means more frequent cleaning, and that the number of people and how long they soak decide it. A tub used every night gets there sooner than one used on weekends.
Between cleanings, Hot Spring and Caldera ask for one small weekly job: check the skimmer basket and weir, and pull out leaves and debris. It's part of the weekly routine anyway.
Check which filter you have
Everything below is written for the ordinary pleated cartridge. A few designs need different handling, and the manuals are firm about it.
- Sundance MicroClean. The 880 Series uses a two-stage filter: an outer pleated cartridge with an insert in the middle. The pleated part gets a hose and, periodically, a spa filter cleaner. The insert gets a light rinse with a low-pressure nozzle and nothing else. Sundance warns that cleaner or a high-pressure nozzle can make it come apart or let impurities back into the water. Take the insert out before the outer filter goes anywhere near a cleaner.
- Hot Spring Tri-X. The Highlife Collection's Tri-X filter is the one cartridge a maker says can go in the dishwasher. More on that below.
- Bullfrog A Series. The Simplicity filter is a flat pleated panel rather than a cylinder. Bullfrog says to spray along the pleats from one side to the other, or simply replace it monthly.
If you sanitize with biguanide, such as Baquacil or Leisure Time Free, read the biguanide note before you buy a cleaner. The order matters.
Before you start
Cleaning it, step by step
- 1
Turn the power off and clear the compartment
Turn the tub off at its breaker. Hot Spring's Highlife manual says to trip the GFCI breaker, in the subpanel or at the end of the power cord.
Lift out anything floating in the filter compartment. If a feeder or mineral holder sits on the filter, take that off first. Jacuzzi's manual covers its chemical feeder and Spa Frog holder, and Sundance's its ease holder. Jacuzzi suggests latex gloves for handling the feeder.
- 2
Take the cartridge out
Four of the five makers have you turn something counterclockwise. The part you turn is different on each:
- Hot Spring: the retainer handle on top of the cartridge. Then lift off the retainer, the cover and the cartridge.
- Jacuzzi J-300: the handle on each cartridge, which unscrews it from the wall fitting.
- Caldera: the filter basket. Push it down slightly, turn it, and lift out the basket and the floating weir. Then pull the cartridge up and out.
- Bullfrog X Series: the filter core cap, once the filter cap and filter plate are off. The cartridge slides up off the core.
- Sundance 880: no turning. Loosen the filter nut for clearance and lift the whole assembly out.
- 3
Hose it down
Stand it on a clean surface and work from the top down, getting the water between the pleats. Unicel says to use a straight-flow nozzle held at a 45-degree angle. Bullfrog says to do the inside first, then the outside, top to bottom on each pleat. Hot Spring notes you may need to turn the cartridge as you spray to get debris out from between the pleats.
Jacuzzi and Sundance both name a high-pressure nozzle on a garden hose. The one exception is Sundance's insert, which gets a gentle rinse only.
No brush. Bullfrog says brushing could damage the filter media, and Unicel says never to scrub it with a stiff one.
- 4
Soak it in a filter cleaner, then rinse
This is the step that deals with the oil, and it's the one a hose can't do. Hot Spring and Caldera tell you to clean the filter with a degreaser every time: soak it by the package directions, then hose it clean. Jacuzzi suggests an overnight soak in a plastic container periodically, and Sundance calls for spa filter cleaner periodically on the outer filter.
How long depends on the cleaner, so read its label. Unicel says to soak any spa cartridge for at least an hour, and that overnight works better.
Then rinse it again, properly. Unicel and Pentair both say to rinse out the oils and the cleaning solution. Whatever stays in the pleats goes into the water when the pump starts. Bullfrog's manual, on cleaning the waterline, says to avoid cleaners that leave soap residue in the water, and residue like that is one of the causes of foam.
- 5
Acid soak, only if it's scaled
Acid isn't part of a routine clean. It's for mineral scale, the gritty crust a degreaser leaves behind.
Unicel has a simple test. After the degreaser and the rinse, put a few drops of acid on a small patch of the media. If it bubbles, there's calcium or other minerals, and a mild acid soak will help. If nothing happens, you don't need acid.
Degrease first, every time. Unicel and Pentair both warn that acid on a cartridge still holding oil or cleaner restricts its flow permanently and shortens its life. Bullfrog says to degrease before any acid product too. Unicel calls acid washing "perhaps the biggest single factor" in cartridges failing early.
The strength is where the makers disagree. Unicel and Pentair say one part muriatic acid to 20 parts water, which is about a quart of acid in five gallons. Bullfrog's X Series manual says one part to 10, twice as strong. I'd start with the weaker mix, since acid is what Unicel blames for early failures. Unicel soaks until the bubbling stops, and Pentair gives each half of the cartridge 10 minutes or until it stops bubbling.
Use a plastic container, rubber gloves and safety glasses, and Pentair adds an N-95 mask. Pour the acid into the water, never water into acid, and never let acid near a chlorine product. Our page on pool chemicals that must never mix explains why. Then rinse the cartridge again.
Bullfrog adds a useful clue: scale on the cartridge means the spa's pH is running high. If you keep finding it, look at the water chemistry.
- 6
Refit it and turn the power back on
On a threaded cartridge, Jacuzzi has you get the air out first. Hold the cartridge under the spa water with the threaded end tilted up until the bubbles stop, and keep it submerged as you thread it in.
Hand-tight is enough. Hot Spring, Jacuzzi and Sundance all say not to overtighten, and Sundance's filter nut should only just touch the filter face. Refit the basket, weir, plate or cover, then turn the power back on.
What to soak it in
A spa filter cleaner is the simple answer. Hot Spring's manuals name its own FreshWater Filter Cleaner, and Jacuzzi and Sundance point you to the cleaners their dealers sell. The filter cleaner on our shelf list does the same job.
Unicel's instructions and Pentair's cartridge guide list two household alternatives:
- one cup of trisodium phosphate (TSP) in five gallons of water, or
- one cup of dishwasher detergent in five gallons of water.
Bullfrog says warm water with a filter cleaner or detergent. Whatever you use, the rinse afterward matters as much as the soak.
If you use biguanide
Biguanide sanitizers, such as Baquacil and Leisure Time Free, leave a gray, sticky film on the cartridge. Unicel says only Baqua Clean or Leisure Time Filter Clean will remove it, so that comes first.
Get the order wrong and you lose the cartridge. Unicel warns that TSP, or any TSP-type cleaner, used before the film is stripped combines with it into a gum that can't be removed, and the filter has to be replaced.
The dishwasher question
Hot Spring's Highlife manual says its Tri-X filter can be cleaned in a dishwasher, using no soap and no dry cycle, and to ask a Hot Spring dealer for details.
That's one filter from one maker. For its standard cartridges, Hot Spring's instruction is a degreaser soak and a hose. None of the other manuals I read mentions a dishwasher at all, so I'd keep every other cartridge out of one.
A second cartridge is worth having
Unicel recommends alternating two sets of cartridges. The practical reason is the power. It has to stay off while the filter is out, so an overnight soak with only one cartridge means a night with the tub switched off.
With a spare, the clean one goes straight back in and the dirty one soaks for as long as the label likes. In a hard freeze, that matters more. I wouldn't leave a tub switched off overnight in freezing weather just to soak a filter.
If your tub holds more than one cartridge, Hot Spring's Highlife manual adds that rotating their positions in the compartment after each cleaning helps them last longer.
When to replace it
A cartridge has no fixed end point. Unicel says the media plugs up gradually over time, and in a spa the culprit is body oil combined with soaps, chemicals and very fine particles. It gives three signs that a cartridge is done:
- the time between cleanings keeps getting shorter
- low flow
- damage, such as a tear in the media or a collapsed center core
Filbur puts it more plainly. If you've cleaned the filter and it still isn't working properly, it's usually time for a new one. Hot Spring's filter sheet adds two visible signs: a cartridge that's discolored, or one showing wear on the rubber.
Broken bands on their own aren't a reason. Unicel says a cartridge filters fine with every band broken or missing, though loose or missing bands are often a sign that it's worn out.
The makers that give a number:
- Jacuzzi: about two years on average, with proper care and water quality.
- Sundance: the pleated filter every 18 months, and the insert every 6 months. The front of Sundance's manual says to replace "the filter cartridge" every six months and that it's designed to be thrown away, but its maintenance section makes clear that means the insert.
- Bullfrog A Series: the Simplicity filter at least every 12 to 16 weeks.
Hot Spring, Caldera and Bullfrog's X Series give no interval.
Finding the right replacement
Start with the part number on the end cap. Filbur embosses its part numbers there and says to check both caps. With no number, Filbur's filter finder works from the end cap's diameter and the cartridge's length, end to end.
Check your warranty before you buy a cross-reference. Bullfrog's manuals say to use only genuine Bullfrog filter cartridges to keep its warranty protection.
What a neglected filter does
A clogged cartridge starves the whole tub of flow. Caldera's manual says it can weaken the jets, limit the flow, or trip the high-limit thermostat, which shuts the entire spa off. Hot Spring's Highlife manual says the same reduced flow through the heater can trip its high-limit and thermal cutoffs. If that happens below freezing and nobody notices, the water can freeze, and Hot Spring treats that damage as poor maintenance that its warranty doesn't cover.
Jacuzzi's troubleshooting section for flow problems has you turn the power off, check the water level, and then check the filter. So if your tub has stopped warming up, a dirty filter is near the top of the list for a hot tub that isn't heating.
The cartridge suffers too. Unicel says plugged media builds pressure across the cartridge until the end caps crack or the core collapses, and it puts that damage down mainly to cartridges that weren't cleaned properly or often enough.
Pool cartridges follow most of the same rules at a much bigger size, and the pool filter cleaning guide covers those.
Go deeperThe rest of the hot tub routineWhat to do after every soak, every week and every few months, and when to drain.For the monthly clean
- Check price
filter cleaner
A hose rinse leaves the oils behind. This is what gets the greasy film.
Frequently asked questions
How often should I clean my hot tub filter?
About once a month. Hot Spring and Caldera say every four weeks, Jacuzzi and Sundance say monthly, and Bullfrog says every 3 to 6 weeks for its X Series. More use means more often. Hot Spring and Caldera also say to check and clean the skimmer basket and weir at least once a week.
Can I clean a hot tub filter with just a hose?
A hose gets the debris out, not the oil. Hot Spring and Caldera say to clean with a filter degreaser every time, and Jacuzzi and Sundance call for a filter cleaner soak periodically. For any spa cartridge, Unicel says to soak it for at least an hour in a filter cleaner, and that overnight works better.
Can I put my hot tub filter in the dishwasher?
Only if it's a Hot Spring Tri-X. Hot Spring's Highlife manual says the Tri-X can go in a dishwasher with no soap and no dry cycle, and to ask a dealer for details. For its standard cartridges, Hot Spring says to soak them in a degreaser and hose them. None of the other manuals I read mentions a dishwasher.
Can I run my hot tub without the filter in?
No. Hot Spring, Jacuzzi, Sundance and Bullfrog all say never to operate or use the spa with the filter out. Bullfrog explains why: the filters and the parts around them are a barrier against a body being held against the suction fitting. Keep the power off until the filter is back in, which is the best reason to own a second cartridge.
How long does a hot tub filter last?
Jacuzzi puts the average at about two years with proper care. Sundance says to replace its pleated filter every 18 months and its inner insert every 6 months. Bullfrog's flat Simplicity filter needs replacing at least every 12 to 16 weeks. Replace any cartridge sooner if the media tears, the core collapses, or a proper clean no longer brings the flow back.
Can I use muriatic acid on a hot tub filter?
Only for mineral scale, and only after a degreaser soak and a rinse. Unicel and Pentair both warn that acid on a cartridge still holding oil or cleaner restricts its flow for good. Unicel's test is a few drops of acid on the media: bubbling means scale. The makers differ on strength, with Unicel and Pentair at 1 part acid to 20 of water and Bullfrog at 1 to 10.
