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How Long Should I Run My Hot Tub Filter?

Perhaps you’ve just purchased a new hot tub and are wondering how long you should run the filter. In this article, I’ll be showing you how long you should run your hot tub filter for it to clean the water effectively.

Hot tub filters are best run for a minimum of eight hours a day, typically separated into two four-hour cycles. This way, you can ensure the water is clean, the filters are not overused, and your energy bill isn’t sky-high.

Before we discuss the issue in detail, let’s first have a look at how hot tub filters work so that you understand why they should run as long as what’s suggested.

Hot tub technician performing scheduled maintenance
Hot tub filter.

What Does the Hot Tub Filter Do?

The hot tub filter removes contaminants, such as body oils, lotions, dirt, and other debris from your hot tub water. Different types of filters use different cartridges. Some last 1-2 years, whilst a few high-quality filters can last 5 years. 

Why Do You Need to Run the Filter?

Running the hot tub filter serves two purposes:

  1. Filters contaminants out of the water
  2. Circulates the water

Hot tub filters are needed to clean the water. Over time hot tubs get different contaminants in them. Including dust, pollen, leaves, dirt from bathers, hair, and all sorts of other contaminants.   

Without a filter, the water in the hot tub would quickly become cloudy, slimy, and unusable and the sanitizer demand, such as chlorine or bromine, would increase. When more contaminants can be filtered out of the water, less sanitizer is necessary.

Circulation of the water is equally important. Lack of circulation, and stagnant water, encourage algae, and other issues. In fact, a hot tub’s wet, warm environment is the perfect breeding ground for bacteria.

How Does a Hot Tub Filtration System Work?

Hot tub filters work by having water pass through them, thus having either the interior polyester, paper, or newer ceramic fiber cartridges trap any unwanted particles in their folds.

Most hot tub filters are designed to allow easy removal, cleaning, and replacement of the cartridges. Cartridges are made up of a core plastic structure surrounded by some type of pleated (containing many folds) medium that acts as the filter.  

Hot tub filters need to be cleaned regularly, about once a week, to prevent them from clogging up. When you do so will depend on the cartridge used and how much debris is present.  The buildup of contaminants is largely dependent on the bather load i.e. how often and how many people use the spa and also the location of the tub. i.e. indoors, outdoors, if you keep it covered when not in use.

Unlike like a pool filter, hot tub filters need to be cleaned more often due to having a high concentration of bathers in a relatively small, when compared to a swimming pool, the body of water.

Minimum Amount of Time to Run a Hot Tub Filter

A hot tub filter should be run for a minimum of two hours, twice a day, for a total of 4 hours. The amount of time you run the filter should be increased based on usage (the heavier the usage, the longer the cycle).

Overall though, you should always aim for the shortest filtration cycle that can keep your hot tub water clean since otherwise, you’ll be wasting unnecessary money on energy costs.

Reviewing some of the user experiences online, there have been those who’ve found that running their filters for four hours a day total has been enough. They’ve found they only need to run the filter for longer if more people are using the hot tub.

It’s important to note that, at the end of the day, how long you run will depend on several factors, such as the type of filter and the amount of use and debris, so only you can experiment and decide on how much is enough.

What is the Maximum Amount of Time Necessary?

Theoretically, it’s possible to keep your filter running all the time, however, this is usually not recommended due to power costs. Instead, you should go for no more than an eight-hour cycle twice a day, and that’s only if you have many people, especially children, frequently using your hot tub.

Is it Okay to Keep it on 24 Hours a Day?

It is OK to keep your hot tub filter running twenty-four hours a day. However, running a hot tub for 24 hours per day is likely to waste energy and accumulate high energy fees. Therefore, most professionals and especially regular users wouldn’t recommend it.

Keep in mind that you’re also putting additional wear and tear on your pump by running it all the time. It will shorten the life of the pump.

Related Reading: 6 Reasons Why Your Pool Pump is Surging or Pulsing (And Fixes)

When Should You Keep Your Filter On All the Time?

You should only keep your filter running all day under these two scenarios:

1. You Use the Hot Tub Heavily

Of course, if you use your hot tub very frequently (a few times per day), and with many people, it may be necessary to run the filter all day long.  

You may notice that your tub isn’t keeping clean or there is a high demand for chlorine or bromine. This is a sign you’re not filtering for long enough.

2. You Use a 24/7 Circulation Pump

Unlike the standard jet pump that circulates the water through the heater and filter, if you have a circulation pump, you will most likely have to run it all day long as that’s what the pump is designed for.

When Are the Best Times to Run a Hot Tub Filter?

If you don’t manually set up the cycle times, you’ll probably notice your hot tub starting its filtration cycle the first time you turn it on, and then run each cycle every twelve hours afterward. Otherwise, here are the best times you should run your filter:

1. After Every Use

It makes the most sense if you run your filter right after each use as that will prevent any debris that made it into the water during your use from attracting any bacteria.

If you have a scheduled time when you typically use your hot tub every day, you can set up the filter to run immediately afterward and then do another cycle twelve hours later.

2. Run it During Off-Peak Hours

In many cities, energy costs are the most expensive during the day, to avoid this you can aim to run your filter cycles during off-peak hours.

Peak hours are typically from 6 am to 10 am, and from 5 pm to 9 pm, so you can try to run your filter at 12 am for example to avoid the times when energy costs are at their highest.

If you do decide to run the tub’s filter at night, consider the noise to your neighbors.

Related Reading: Why Your Hot Tub Pump is Noisy & How to Fix It (Quieten it)

How to Determine How Long to Run a Hot Tub Filter

The best way to determine how long you should run your spa’s filter is to simply experiment with what you have since the time depends largely on your spa, usage, and local water quality.

If you take a look at some of the hot tub forums online, you’ll notice many people asking others for advice on how long to run their filters. They don’t always follow the manual, and will often experiment to see what’s best for their situation.

What Happens if You Don’t Run It Enough?

If you notice any of the following situations with your hot tub, it’s an indication that you need to run your filter more. It could also mean you are not keeping the chemicals at the recommended levels.

  • The water is getting cloudy
  • The hot tub is developing an algae-like smell
  • You’re adding what seems like a lot of sanitizers (sanitizer level always seems low)
  • Foam or biofilm is appearing on the water’s surface or around the waterline

If you notice these, it’s best for you to shock your tub or Jacuzzi to bring the sanitizer levels up and increase the filtration cycle time. You may also have to drain and refill your hot tub with new water.

Spa hot tub foam biofilm
Hot tub foam/biofilm caused by lack of filtration and cleaning.

Related Reading: How to Fix a Slimy Feeling Hot Tub (Clear Biofilm)

Final Thoughts

Though I’m able to provide you a range of approximately how long you’ll need to run your hot tub filter, it’ll be up to you to ultimately decide on exactly how long is needed. Once you’re able to find that balance between keeping your water clean and your energy bills down, you’ll realize that keeping your hot tub clean isn’t so tough after all.

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