The Complete Guide to Hot Tub Water Color Problems: Green, Brown, Yellow, Pink & White


The water in my hot tub has turned several different colors over the years, which certainly put me into a bit of a panic when I first encountered the problem.

However, from my own personal experience, I can assure you that the good news is it’s nothing to worry about. In this in-depth guide, I’ll show you how to identify and fix your discolored spa water so that it turns crystal clear again.

What color has your water turned?

Green water

Green water in a hot tub is either caused by algae or high levels of copper. Algae forms when there is an insufficient amount of sanitizer and the water is exposed to UV light for extended periods of time. Water sources containing high levels of copper cause a chemical reaction to occur, turning the water green.

If the water in your spa has turned green, the first thing to check is whether or not there is a slimy, slippery, or sticky feel on the side of the hot tub shell. This indicates whether the cause is from algae or excess copper levels.

Algae blooms

A slimy, slippery, or sticky feel likely indicates algae growth. Algae flourishes under sunlight, which is why this is a common problem for spa owners that leave their spa uncovered for extended periods of time.

While insulated covers go a long way to preventing algae blooms, it’s still possible for them to grow beneath a cover if sanitizer levels are low, if there is a pH imbalance, or if the filter is dirty or worn out.

Never use your hot tub if algae have turned the water green as it can damage your health. The CDCOpens in a new tab. warns that bacteria found in hot tubs have been known to cause diarrhea, skin rashes, ear infections, and Legionnaires’ disease.

How to treat an algae bloom

In order to treat green hot tub water, the first thing to do is to balance the alkalinity and pH levels. Once balanced, use a chlorine-based shock to boost the sanitizer levels.

Next, you’ll need to remove the filter, give it a quick rinse, and place it in a chemical soak for 24 hours. For more information, see my guide to filter maintenance.

If the water has been green for an extended period of time, it’s best to drain the spa water, disinfect the empty spa shell with surface cleaner, and replace the filter cartridge.

To prevent the algae from returning, make sure to test and adjust sanitizer levels on a weekly basis and ensure a regular filter cleaning routine. Also, make sure that your hot tub cover is in good order and is well maintained.

Investing in an inexpensive floating blanket can also go a long way to preventing algae, as well as saving you money on spa chemicals and your energy bill.

Note: For persistent problems with algae blooms, treat the water with this algaecide control product to eliminate algae and prevent outbreaks in the future.

High levels of copper

If the sides of the hot tub don’t feel slimy, then this indicates that high levels of copper and other minerals have caused the water to have a bright green tint.

The copper minerals may be coming from copper piping that carries your water. Alternatively, hard water sources, such as that found in cities and groundwater wells, often contain high levels of metals.

Just like how an old copper penny turns green, the same thing is happening to your spa water as a result of a reaction between the copper and the chemicals in the water.

How to treat copper levels

In order to treat high copper levels, you’re going to need to drain the spa and refill it with fresh water using a hose fitted with an inline pre-filter (more information below). Once filled, you’ll add an entire bottle of a metal control product called Metal Gon.

The highly concentrated formula sequesters copper and other metals so that they can be got rid of by your hot tub’s filter. This stops the water from turning green and also prevents staining to the spa shell.

I recommend buying several bottles as you’re going to use an entire bottle of Metal Gon every time you fill-up. You’ll also save money buying in bulk, too.

Metal Gon can also be combined with Defender, a scale and control chemical, to help prevent an excess build-up of minerals that can damage the heater and cause other equipment to fail prematurely.

If you live in an area where the water contains high levels of copper and other harmful metals, you must attach an inline pre-filter to your hose before filling your spa.

Note: If the hot tub water has turned green after adding shock, it’s the result of the oxidization reacting with the copper minerals. To remove, treat the water with spa metal remover.

Attach a pre-filter

Pre-filters get rid of up to 98 percent of metals and other impurities in the water. This makes for fresher water that’s easier to balance, which saves you time and money by having to use fewer chemicals.

Brown water

Brown, orange, or rusty-colored spa water is usually the result of iron and other metals becoming oxidized. As well as discolored water, it can cause a build-up of scale and stain the surface of your hot tub.

Brown water can also be caused by rusting components or a deteriorating heater connected to the plumbing system.

If you have iron in your hot tub water, then it must be treated immediately as it’ll continue to turn the water brown every time you add more chlorine.

If the water suddenly turned brown in the hours after adding shock, then it’s likely to have been caused by the chlorine oxidizing the high levels of iron in the water. It may also occur when making large adjustments to the pH levels.

Brown water may be the result of contaminated water. Water suppliers may have little alternative but to use up what water they have during periods of hot weather, causing particulate matter from the bottom of the tanks to enter the water source.

How to fix brown water

To fix brown spa water, you’ll need to force the iron back into solution using this sequestering agentOpens in a new tab.. It binds the iron particles into larger clumps, which allows the filter to remove them from the water.

Avoid filling your spa with excess metals by using an inline pre-filter that removes the majority of the impurities. Pre-filters are essential if you live in a hard water area or for those that source their water from a groundwater well.

Filling your spa with cleaner water makes it far easier to balance the water chemistry and requires fewer chemicals to do so, which saves on the cost of having to buy the pre-filter.

Yellow water

Yellow-tinted water in a hot tub is mostly caused by either an algae growth or a high bromine residual combined with a low pH.

Yellow algae, also known as mustard algae (class XanthophyceaeOpens in a new tab.), causes the water to turn a greenish-yellow. This type of algae growth has an appearance that is yellowish-gold and powdery and deposits itself in sheets across the surface of spa water.

While yellow algae are easy to brush off, it’s a highly resistant type of algae that’s difficult to treat. It contains natural properties to defend itself against chlorine and bromine sanitizers.

Yellow algae thrive in warm, dark, and shady conditions, making any small crevices in your hot tub the perfect spot for it to hide and multiply.

Note: If you leave the cover off your spa for an extended period of time, it’s also possible for excessive amounts of pollen to cause hot tub water to have a yellow tint.

Yellow spa water may also be caused by extremely high levels of bromine sanitizer and a low pH level, which can cause the water to turn a yellow-red color. Once the total alkalinity and pH have been properly adjusted, the water should become clear again.

How to fix yellow water in hot tub

The first thing to do is brush off any algae from the surface of the water and balance the alkalinity and pH levels

Next, turn off the spa heater and add very high levels of chlorine-based shock to the water. Keep the cover off and run the pump to allow the water to circulate for several hours.

It’s well worth using this spa algaecide to help fight the yellow algae after the initial high chlorine shock treatment.

Test the water after 24 hours. If the free chlorine or bromine levels have dropped to 0 parts per million (ppm), add more shock until the sanitizer levels stabilize.

SanitizerAcceptable rangeOptimum level
Chlorine1 – 3 ppm3 ppm
Bromine3 – 5 ppm5 ppm

Once the spa holds its sanitizer levels, drain all of the water and disinfect the empty spa shell with surface cleaner. Do your best to clean any small crevices in the hot tub shell where the algae may be lurking.

You must ensure that you rinse thoroughly and remove all of the standing water in areas such as the footwells. I find it easier and much quicker to do this with my inexpensive wet/dry vac.

Finally, use bleach to wash down your insulated cover and replace the filter cartridge with a new one.

Pink water

The pink slime in your spa water isn’t a type of algae but a biofilm formed by colonies of the bacterium Serratia marcescens.

The bacteria is a close cousin of white water mold and is common around the world, often being found in bathrooms where it displays as pink rings and streaks.

Water turning pink isn’t very common in hot tubs and only happens in very mature colonies. The reason why Serratia marcescens is able to grow is that it’s highly resistant to chlorine, bromine, and mineral sanitizers.

This form of bacteria thrives in dark and damp conditions and growth is accelerated where there are phosphorus or fatty residues such as soap or shampoo.

As well as finding its way into spas from bathers, it’s also introduced to hot tubs by the wind and rain because the bacteria is airborne.

Warning: While Serratia marcescens is usually nothing to worry about, it can cause problems for people whose immune system is severely compromised. If you wear a catheter, respirator, or another medical device, you should avoid bathing as it can provide a means for the bacteria to enter your body.

How to treat pink water

You’ll need to super-chlorinate the water by adding a significant amount of chlorine-based shock in order to raise levels to at least 30 ppm.

Next, use this enzymatic purgeOpens in a new tab. to clean the lines and any crevices where the bacteria like to hide away.

Finally, drain all of the water from the spa and clean with surface cleaner. Use bleach to thoroughly soak and clean all components, including the main cover. Rinse everything thoroughly and remove all standing water from the spa.

Because the bacterium is highly resistant to cleaning chemicals, it’s better to replace the filter rather than attempt to clean it.

White water

If the water in your hot tub is no longer crystal clear but has become white and milky, then it’s likely to have been caused by one of the following:

  • clogged filters
  • high alkalinity
  • pH imbalance
  • low sanitizer levels
  • high calcium hardness
  • pump issues
  • biofilm build-up

The good thing is that there’s no need to worry as the solution is pretty simple. The only thing you’ll need to work out is what caused the clouding issue in the first place.

Thankfully, you can check out my complete guide to cloudy hot tub water. The in-depth guide will enable you to identify the cause so you know which steps to follow in order to treat and fix the problem.

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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