How Do I Know if My Hot Tub Filter Needs Changing?


The frequency with which you use your hot tub along with the number of users determines how often it’s necessary to replace the filter. Because there’s no one way to answer exactly when it’s time to change it out, here is a list of the most common signs to look out for.

Signs that it’s time to replace your filter are when:

  • Filter is more than 12 months old
  • Filter is impossible to get clean
  • Filter clogs up quickly
  • Spa water becomes cloudy after cleaning
  • Water flow is restricted
  • Filter cartridge is damaged
  • Filter is heavily stained

I’m going to explain exactly what to look for so you’re left in doubt as to when it’s time to order a replacement. Later on, I’ll show you six simple things you can do to prolong the filter’s lifespan and save you money.

7 signs that you need a new spa filter

Filter cartridges are the kidneys of your hot tub, functioning to ensure everything stays healthy. Their importance means that it’s essential that they’re in good working order.

Here are the seven signs that it’s time to replace your filter.

1. Filter is more than 12 months old

Hot tub filters are designed to last approximately one year. Depending on the quality of your filter, it should be able to withstand 10 – 15 chemical rinses.

Filters are inexpensive and play a key role in keeping your spa clean and clear, so it’s not worth trying to save a few pennies by using them longer than you should.

Besides, any money you save by not replacing the filter will only be lost on having to add extra chemicals to balance the water due to lack of filtration. Worse still, dirty hot tub filters may even void your spa’s warranty.

Spa filters naturally degrade over time. The constant flow of water causes the woven fibers to separate, allowing a greater number of larger and larger particles to pass through unfiltered.

And because the filters become less and less efficient over time, they need to be cleaned more frequently.

Ironically, the damage to the fibers is exacerbated by the cleaning process, with the rinsing and cleaning also stretching the fibers apart.

However, rinsing and cleaning are part and parcel of filter maintenance and do not mean you shouldn’t bother.

If you notice that the time between chemical rinses has increased to fortnightly instead of monthly, then it’s a sure sign that it’s time to replace the filter.

Even if you don’t use your spa all that often, or it’s been shut down for a long period of time, then you still need to replace the filter after 12 months.

And if your hot tub sees a lot of action, or it regularly sees a high bather load, then it’s well worth replacing the filter more often.

2. Filter is impossible to get clean

In order to prolong the life of your filter and keep your hot tub running smoothly, you should have a regular cleaning routine in place. For most users, it’s necessary to perform the following:

  • Weekly rinse: rinsing the filter with fresh, clean water using a hose fitted with a pre-filter
  • Monthly chemical rinse: spraying the filter with specially formulated chemicals and rinsing after 15 minutes
  • Quarter chemical soak: soaking the filter in specially formulated chemicals for 24 hours, rinse, and allow to dry

Despite the number of chemicals you use or how thorough you are, it becomes impossible to get the filter clean after a while. Once you notice that no amount of cleaning can get your filter looking like new, it’s time to replace it.

3. Filter clogs up quickly

As we’ve just seen, it should only be necessary to rinse your filter cartridge with a chemical spray once per month to keep the water flowing freely.

But if the filter is clogging up within just a few days of cleaning, then it’s likely coated with mineral scale or an oily film. Unfortunately, these can be very difficult to remove.

Thorough cleaning between the fibers of the filter using spa filter cleaner and an Aqua CombOpens in a new tab. that attaches to your hose for improved cleaning may work to remove debris, crusty deposits, and oils; however, the filter must be replaced if it continues to clog up shortly after cleaning.

4. Spa water becomes cloudy after cleaning

Every time you use your spa, you introduce contaminants that cause the water chemistry to become unbalanced.

So long as the filter is in good working order, it’s able to filter out the majority of those contaminants.

However, if the filter becomes clogged or is not positioned properly, it isn’t able to do its job, leading to cloudy water.

Removing the filter and giving it a deep clean in a chemical soakOpens in a new tab. for 24 hours might well resolve the problem.

Cloudy water is sometimes caused by a chemical imbalance, so you should test and balance the water at the same time you perform the chemical soak in case the clouding hasn’t been caused by the filter.

But if the cloudy water returns shortly after cleaning the filter and balancing the water chemistry, then it’s time to replace the filter.

5. Water flow is restricted

If you notice that the water exits the filter with decreased pressure, then it means that the filter is clogged with dirt and debris.

Unlike a swimming pool, hot tubs are very small bodies of water. With each bather introducing contaminants, it doesn’t take long before there’s a large concentration of particles in the water.

In addition to clouding, water that isn’t properly filtered can cause damage to the mechanical parts inside the spa.

It also increases the amount of time it takes the spa to heat as the water isn’t able to flow as it should.

Again, carrying out a chemical soak and a thorough clean between the pleats might resolve the problem, but the filter must be replaced if it doesn’t.

6. Filter cartridge is damaged

Filters with cracks, splits, or holes don’t occur all that often, but it is entirely possible. Trying to repair a broken filter isn’t possible, so a replacement is the only option.

Needless to say, cracks and holes of any size mean that the filter isn’t going to be able to prevent particles from passing through, leading to unsanitary water.

Cracks usually develop on the colored, rubber end caps or across the central support cage.

Cracks in the rubber end caps are often caused by a spa filter pump that’s too large for the size of the filter.

If the pump is inappropriately sized for the filter, the extreme pressure can cause holes to develop, so make sure that the pump and filter are the right match.

Filters also need to be replaced if you notice that the tips of the pleated fabric are no longer smooth.

When the edges of the pleats unravel, they become fuzzy, which reduces the filter’s ability to trap dirt and debris.

The problem is usually caused by cleaning the filter with excessive water pressure, imbalanced water, or using too much sanitizer.

7. Filter is heavily stained

Metals such as iron can cause staining to occur on the filter fibers, turning them a light orange-brown color. It’s even possible that the filter to turn yellow, gray, green, or even purple.

While a stained filter isn’t always a sign that immediate replacement is necessary, it’s something to keep an eye on.

It can be difficult to remove staining completely using spa filter cleanerOpens in a new tab., but never be tempted to use harsh chemicals or alternative cleaning methods to get the fibers white again.

Heavy staining may cause areas of the filter cartridge to not work properly as the staining clogs the microscopic filter pores.

If you’re in any doubt as to whether your spa filter is able to filter out particulate matter, then order a replacement as soon as possible.

6 ways to prolong the life of your filter

Regular maintenance not only prolongs the life of your filter but also your hot tub too. Here are six simple ways to increase the lifespan of your filter.

1. Shower before getting in

Taking a quick shower dramatically reduces the number of contaminants you introduce into the water.

Care products such as shampoo, deodorant, hairspray, makeup, and so on cause the water chemistry to be thrown out of balance, increasing the number of chemicals needed and making your filter work extra hard.

Rinsing your swimwear off with clean water instead of washing in laundry detergent is also an effective way to increase the filter’s lifespan as well as prevent foaming.

2. Frequently perform full water drains

For most hot tub users, it’s recommended to perform a full water drain every three to four months. Getting rid of the water and starting afresh prevents your filter from becoming clogged up by old, stale water.

Before draining, use Oh YukOpens in a new tab. to get rid of any traces of biofilm lurking in the plumbing. Once drained, sanitize the empty hot tub shell using a dedicated spa surface cleanerOpens in a new tab..

Draining and cleaning your hot tub is a simple way to limit the number of chemicals you have to use in order to keep your spa water safe and balanced.

The older the spa water gets, the less effect chemicals have as the water becomes oversaturated, meaning you have to use more and more to achieve the same effect.

3. Invest in an insulated cover and blanket

Investing in an insulated cover ensures that the majority of dirt, debris, and other foreign matter is unable to enter your hot tub. Less debris means less work for your filter.

You can further increase the efficacy of the cover by combining it with an inexpensive floating blanketOpens in a new tab.. Blankets are especially useful at weekends or during social gatherings when you’re in and out of the tub all day long.

Most hot tub owners invest in a cover but few utilize a floating thermal blanket. There are so many other money-saving benefits, which is why I wouldn’t be without mine. I encourage you to read about the advantages of a spa blanket in my full-length article.

4. Attach a pre-filter to your hose

Unless you live in an area with extremely soft water, then you should have a pre-filter attached to the end of your hose.

Pre-filtersOpens in a new tab. prevent up to 98% of damaging particles from entering the hot tub. This means that your spa filter doesn’t have to work unnecessarily.

The fact that 98% of the particulates have been removed from the water while filling also means that you won’t use as many chemicals trying to balance the water chemistry.

5. Test and balance your water chemistry weekly

Having to test and balance your spa water can quickly become tiring, which causes many to let it fall by the wayside.

But failing to do so will have your poor filter working overtime, causing it to age and fail prematurely.

Performing a weekly check using a drop test kitOpens in a new tab. or test stripsOpens in a new tab. not only prolongs the life of the filter but also prevents common water chemistry issues that can be expensive and time-consuming to put right.

6. Proper filter maintenance

For average hot tub use, a weekly, monthly, and quarterly clean are enough to achieve maximum life from your filter. Spa filters should only ever be cleaned with specially formulated spa filter cleaner.

Never use a pressure washer. The stream of water you use should be gentle enough to not cause tearing of the filter fibers. After rinsing and cleaning, always allow the filter to dry completely before replacing.

While household cleaners can sometimes be okay for cleaning the hot tub shell, you must steer clear of them when cleaning filters to prevent issues with foaming.

When it’s no longer possible to get the filter clean, you might be tempted to use bleach to clean the filter in order to get it sparkling again. However, bleach is far too harsh and will damage the media fibers.

Unfortunately, hot tub filters don’t last forever. They’re an integral part of your hot tub and must be replaced as soon as they show signs of not functioning properly.

Never be tempted to use your hot tub without a filter. Running the pump in a spa for long periods of time without the filter can lead to clogged pump impellers, as well as a rapid decline in water quality.

By having a spare filter always on hand that you can install, you won’t have to wait around to enjoy your hot tub.

Did I cover everything?

I always try to provide the most relevant and up-to-date information I can in all of my articles. Saying that, feel free to shoot me an email using the contact form if you think this article is lacking in some way, or if you’ve been left with any doubts.

Thanks for reading and happy hot-tubbing!

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