Clear hot tub water

Clear Hot Tub Water: How to achieve it and why it goes bad

Nothing is more inviting than clear, sparkling hot tub and swim spa water. The temptation can be overriding to get in and soak the troubles of the day away. But when you remove the cover only to find cloudy, milky or foaming water, the last thing you’ll want to do is climb in and immerse your body in it.

And for good reason, because cloudy, milky, dull or foaming water is a signal that something is wrong with it.

As a general rule, clear hot tub water is the result of a well-managed water care regime, with the pH, free Chlorine and Total Alkalinity being measured daily. Clear water has very few pollutants, particles and contaminants present which aids clarity.

Let’s look at a few factors to consider when keeping your hot tub or swim spa water looking as good as possible, and safe for your bathers.

How do you know if your hot tub water is bad?

OK, the photo above is an exaggeration – we hope!

We all know what a clear pool of water looks like. On a sunny day it should sparkle and glisten, and you should easily be able to see the bottom of your hot tub or swim spa tank when the pumps or jets are not working at full tilt.

Once you lose the clarity of the water it’s because there is something else present that shouldn’t be. As with a glass you draw from from your kitchen tap, water will be clear until you add something to it.

Hot tub water that has gone bad will be either cloudy, milky, or dull in appearance, or it will foam excessively when the pumps or jets are turned on.

A water care regime employed regularly will remove pollutants and contaminants from the water. If it is done in a haphazard fashion, or insufficient water treatment chemicals are added where necessary, the hot tub water will suffer.

In addition you should clean your filter cartridge on a weekly basis to remove dirt, oils and grime, and replace it when necessary. The filter plays a crucial role in trapping particles before they are circulated back into the spa.

How long can spa water go untreated?

There isn’t a set time for how long you can leave your hot tub or swim spa water untreated. It could be fifteen minutes or twenty four hours, just as there’s no set time to get an unlocked car broken into.

As soon as a pollutant enters the water and bacteria gets chance to multiply the water becomes less safe for bathers. If this process continues it will soon become hazardous to use.

The most common source of contaminants of water is the bathers themselves, so keeping the cover in place when the spa isn’t in use won’t lessen the need for testing. Human skin that is free from lotions, etc will still secrete oils and fats, and this will need to be dealt with by your treatment chemicals on an ongoing basis.

Water that isn’t treated for any length of time can be extremely difficult to re-balance and restore so that it is fit once more for bathing.

In addition to water quality impacting the bathing experience, neglected water can also form scale in the hot tub which ultimately could impact its performance and even its lifespan.

How often should hot tub water be changed?

Hot tub and swim spa water should be changed every three to four months.

Emptying and refilling the spa is necessary as there will be a build-up of total dissolved solids in the water. These cannot be removed from the water and so a complete water change is the best answer. If your water is well maintained via a good testing programme then the life of the water can be extended.

Why does hot tub water foam up?

Many of the products that bathers may bring with them into a hot tub or swim spa could cause excessive foaming in the water, namely the residues of laundry detergents, soap, deodorant, make up, body lotions, shampoos and conditioners. This is why asking users to shower before using your hot tub or swim spa is always advisable.

Soft water can also decrease the surface tension causing foam to easily form, so test the calcium levels in your water to ensure an adequate reading of over 250 ppm (parts per million). Always turn off your water softener before filling your hot tub or swim spa.


A well-maintained hot tub or swim spa that is subject to regular water testing and the application of treatment chemicals as appropriate will drastically improve the chances of your water remaining clear and sparkling.

Cleaning the filter cartridge on a weekly basis and replacing it when necessary will also assist the removal of contaminants that will affect the clarity of your water.

Happy, safe bathing!

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