Can You Run a Hot Tub Without a Filter?


It’s all too easy to forget to order replacement products for your hot tub. If you fancy a soak or you have a party coming up, you might be tempted to use your spa without a filter. So is a filter really necessary to run a hot tub?

A hot tub should not run for extended periods of time without a filter. Doing so results in excessive use of sanitizers, cloudy and smelly water, a build-up of bacteria and scum, staining and discoloration, a water chemistry imbalance, and dirt and debris that can clog the pump and plumbing.

Using your hot tub without a filter is going to end up costing you more money in the long run. But what about when you need to remove the filter to clean it?

How long can a hot tub run without a filter?

If you need to run your hot tub without a filter for whatever reason, then there are a few precautions you should take.

Ensure that the spa jets are turned down low and that the pump is running at a low speed. Avoid running the pump for too long without a filter as it can lead to clogged pump impellers and a rapid decline in water quality.

Of course, as part of your regular filter maintenance routine, you’re going to have to take the filter cartridge out in order to clean it with a chemical spray or soak.

A chemical soak takes 24 hours, which means your hot tub is out of action during that time. Instead of resisting temptation and taking a dip with no filter in place, I recommend always having an extra filter cartridge on-hand.

Note: A damaged or dirty filter can be just as harmful as using no filter at all, so ensure a regular cleaning routine to avoid clogged filters. Signs that your hot tub filter isn’t working properly and needs replacing immediately are:

  • Cracks or holes in filter cartridge
  • Fuzzy filter pleats
  • Filter clogs again shortly after cleaning
  • Heavy staining (gray, green, yellow, or purple)
  • Filter is still dirty after 24-hour chemical soak
  • Filter is more than 12 months old

Check out my complete guide to filter maintenance and replacement for more in-depth information.

7 reasons why you must use a filter in your hot tub

In order to keep the body healthy, our kidneys filter the blood of toxins so that they can be removed as waste products.

In much the same way, a hot tub’s filter rids the water of harmful contaminants to ensure that the spa remains safe for bathing.

Each time you step into your hot tub, you introduce some 100 million new bacteria into the water. These bacteria are made up of natural bodily fluids and the plethora of personal care products we use in our modern lives.

Another source of contaminants for hot tubs is from the elements. The wind and rain carry a whole lot of dust and debris that make their way into the water while we’re bathing.

And as the water is exposed to UV light from the sun’s rays, it kills off the chlorine. A lack of chlorine sanitizer results in the growth of certain algae that thrive in the warm and humid conditions found in your hot tub.

With no filter installed in your spa, it’ll not only lead to an accumulation of scum but a whole host of other problems that can affect both your health and your wallet. Let’s take a look.

Having to use more sanitizing chemicals

The reason we add sanitizers such as chlorine or bromine into the water is so that they can work alongside the filter to ensure that the water remains crystal clear and safe for bathing.

However, because the sanitizer isn’t accompanied by a filter cartridge, it has to work extra hard to keep the water sanitary. With the sanitizer working so hard, it doesn’t last long before getting used up.

The only way to deal with this is to add far more than is usually necessary to keep levels within a safe range. This means devoting more time to testing and adjusting the water chemistry, as well as wasting money on extra chemicals.

Cloudy and smelly water

With the majority of the contaminants remaining inside the spa, it eventually results in the water developing a foul smell that you’re definitely not going to want to soak in.

And if the chlorine levels become too low, it leads to chloramines forming in the water. Chloramines are what give off that harsh and obnoxious “chlorine” smell that most wrongly assume are the result of adding too much chlorine.

Another effect of high levels of contaminants is the spa water turning milky and cloudy. Just think of how your bathwater changes color as you wash with soap.

Because the personal care products you introduce aren’t being removed by filtration, your hot tub is spending months at a time heating them up, resulting in a cloudy soup of bacteria. Yuck.

Bacteria build-up

Another job your spa’s filter cartridge has is to filter out contaminants that can lead to bacterial growth. By trapping them inside the filter, it makes it difficult for the bacteria and other microorganisms to grow.

However, with no filter in place, the algae have the perfect breeding ground to grow and flourish. Algae blooms cause your spa water to become discolored, turning the water an unsightly shade of green or yellow.

As all the deodorants, soaps, shampoos, cosmetics, laundry detergents, and bodily fluids circulate around the plumbing, it causes a build-up of nasty gunk inside the plumbing.

This gunk is known as biofilm and is very harmful to your health. The only way to deal with biofilm is to use a special line flush product to clean the pipes before then having to drain all of the water and start again.

Staining and water discoloration

So far, I’ve shown you how a lack of filtration can result in a scummy build-up of bacteria, algae, and biofilm that turns the water cloudy and smelly. But that’s not all. It also results in staining to the hot tub shell.

Scum build-up can soon start to stain the shell brown, blue-green, or yellow, while also giving off obnoxious odors.

And as you fight to stay on top of sanitizer levels, you might well end up overcompensating by adding too much.

Using too much sanitizer can also cause staining, turning the sides of the hot tub brown, red, or yellow. And another side effect of over-chlorinating the water is that it becomes too acidic, resulting in damage and corrosion to the acrylic shell.

Water chemistry imbalance

The filters work alongside sanitizing chemicals to ensure that the alkalinity and pH remain balanced. A build-up of contaminants in the water due to a lack of filtration will soon create an imbalance in the water chemistry.

As the chlorine gets used up quickly because it’s having to do twice the work, it leaves the alkalinity defenseless.

Alkalinity acts as a buffer, or “bodyguard”, to prevent movement to the pH levels. With no control over the total alkalinity, it soon causes chaotic fluctuations in the pH that can be a nightmare to balance.

Dirt, dust, and debris

No matter how careful we are, it’s inevitable that dirt and debris such as leaves and twigs find their way into the water when the cover is off.

While chlorine and bromine sanitizers can attempt to protect and sanitize the water from these outside contaminants, something it can’t do is remove them from the spa water.

Without a filter, you would have to use a skimmer to regularly skim the water’s surface of any debris that’s landed in the water.

Unfortunately, while it might be easy enough to get rid of large debris such as leaves, it’s going to be impossible to remove the tiny dust particles floating on the water’s surface and the personal care products that have been washed off our skin.

Pipes get clogged up

With a lack of filtration, all that dirt, dust, and debris is free to circulate around your hot tub’s plumbing.

Left long enough, the pipes will start to become blocked. This causes a disruption to the flow of water, resulting in damage and premature failure to the heater and pump.

And because the flow is restricted, it means that there is a lack of pressure coming out of the jets. A lack of pressure means less turbulence in the water, so the heater has to work much harder to raise the temperature and evenly distribute the heat.

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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