Why Your Hot Tub Water is Green



Green is a nice color. It’s actually my favorite color. Just… not when it comes to hot tub water.

If you’ve walked out back for a nice, relaxing dip in your spa and noticed a beautiful green color in place of the sparkling blue, chances are you’ve got an algae bloom on your hands. 

Dealing with an unusable hot tub is no one’s cup of tea but the good news is that it’s easily fixable and preventable in the future with just a few simple tricks… and a bit of elbow grease.

Why Your Hot Tub Water is Green

There are a couple of reasons your hot tub water might have turned from its usual refreshing clear-blue to the sickly color of the Wicked Witch of the West. The most common is, unfortunately, an algae infestation.

A good way to determine if algae is to blame is to run your hand along the inside wall of your hot tub. If it feels a bit slimy… bingo! You’re a winner. (Sort of.)

Algae: The Nemesis of Hot Tubbers Everywhere

How did algae get in your hot tub? An excellent question. There are lots of ways this greenish pest can make its way into your life and add one more thing to your ever-growing to-do list.

Before we can fix the problem, however, we have to know what caused it to begin with. So let’s take a look at the main causes of algae and see if we can solve the riddle.

  • Busted Filter – If your filter isn’t functioning properly or you’re not running it enough, your water isn’t being cleaned. All of the water in your hot tub needs to be filtered at least once per day to do its job right. If your filter is on the fritz, you may have found your answer.
  • No Cover – Not using a hot tub cover is a big no-no and can lead to your sanitizer breaking down too quickly and causing inevitable algae growth. If your hot tub sits in direct sunlight, it is essential that you use a cover.
  • Not Enough Sanitizer – Algae loves warm water and a lack of chlorine. If you’re not adding enough chlorine to your hot tub, there’s a good chance you just made the algae right at home.
  • Someone Brought It In – Stowaway algae? This isn’t too likely unless your friends and family swim in ponds and lakes right before they jump into your spa, but it is a possibility. Algae can be transferred via clothing and swimsuits from its natural habitat or from another algae-infested pool or hot tub.

Copper: The Less-Likely Possibility

If your hot tub water is a more vibrant color of green and not slimy, there’s a good chance this mineral might be the cause of your green spa. Copper can be introduced to hot tubs through well water, copper heating elements in gas-powered spa heaters, and copper plumbing.

The good news is that if copper is the culprit, you have a much easier fix than with algae. To make your hot tub blue again and keep your hair from turning green, simply add some liquid metal remover (or metal sequesterer) to your spa.

How to Avoid a Green Hot Tub (in the future)

Keeping algae out of your hot tub is as simple as avoiding the causes we talked about above. 

  • Check the Filter – Clean your filter regularly and don’t forget to replace it when it starts to slow down. It’s a good idea to keep an eye on the filtration system and make sure it’s functional at all times. 
  • Test & Balance the Water – Make sure you are testing your water frequently and adding sanitizer on a regular basis and extra when needed. Letting your sanitizer levels fall below recommended standards can result in algae and bacterial growth and worst of all — an unusable hot tub.
  • Always Keep it Covered – Even if your hot tub is indoors or in the shade, it’s a good idea to keep it covered when it’s not in use. The more debris, dust, pollen, and other organic material that is introduced to the water, the higher the chances of an algae or bacteria hostile takeover.
  • Rinse-Off Before Hopping In – What happens at the lake, stays at the lake. Okay, even if you’re not going straight from the lake into your hot tub, it’s a good idea to have everyone rinse off before entering the hot tub. This will help to lower the probability of introducing algae or other forms of contamination to the hot tub.

How to Eliminate Algae in Your Hot Tub (right now)

Clear your schedule for the day and put on your battle gear because today we’re going to war with algae. The bad news is that it’s going to be a lot of work but the good news is that by the end, your hot tub will be sparkling clean and algae-free.

Step #1 – Drain & Scrub the Shell

First things first. There’s no hope for the water in your hot tub so it’s got to go. Drain the water from the hot tub completely and then set to work scrubbing the interior. Make sure to use some kind of disinfectant, such as a hot tub cleaner or a bleach solution to remove all algae contamination.

For bonus points, soak all spa items such as pillows, floaties, etc. in a strong bleach solution to prevent recontamination.

Step #2 – Deep Clean or Replace the Filter

Next, give your filter the deep clean it needs. If there is algae in your hot tub water, there’s a very good chance that it has made its way to your filter too. Using a filter cleaner is a great idea but for extra peace of mind, remove the filter and soak it overnight in a chemical rinse to be sure that all of the algae is dead.

If you’re not convinced this did the job, now might be a great time to go ahead and replace your filter. That way there is no possibility of an algae recurrence.  

Step #3 – Refill the Hot Tub

Once your hot tub shell and filter are squeaky clean, it’s time to refill the hot tub. You could just turn on your hose and hope for the best, but we recommend using a hose filter to avoid any metal contamination from the tap water.

Step #4 – Wash the Hot Tub Cover

Think of your hot tub cover like a pot lid on top of a boiling pot on the stove. It’s going to be collecting condensation from the steam and with it, whatever algae that might be living in the water. 

You’ll need to scrub your cover, using a diluted bleach mixture or a special vinyl cleaner to make sure the algae is gone for good. 

Step #5 – Shock, Wait, & Shock Again

Now it’s time to give the algae the one-two punch with a double dose of shock. Shock it once, then wait, then shock it again to make sure that algae is never coming back.

Step # 6 – Test & Balance 

Once you’ve shocked and circulated the water, grab your test kit and test the hot tub water just like you normally would. If any levels are out-of-whack, correct them by adding sanitizer or other chemicals before retesting again. 

Remember, keeping your hot tub water properly balanced is the best way to avoid a repeat performance of “Night of the Living Algae”.

But… My Water is Another Color!

Uh oh, instead of a beautiful blue spa, you’ve uncovered it to find a very different shade. Unless you’ve added a colorful dye to your hot tub (for whatever reason) it shouldn’t be a multi-colored body of water. 

Yellow Hot Tub Water

If your hot tub water has turned yellow or has a yellow tinge to it, you may be facing the dreaded yellow algae. Yellow algae is a major pain, mostly because it is resistant to most sanitizers, even at the proper levels. It loves dark, warm water — so you may find it in your hot tub if you’ve left the cover on for extended periods of time.

The best way to oust this pest is through a thorough balancing of the water, followed by a high-level chlorine shock.

Pink Hot Tub Water

Pink algae can cause your hot tub water to look very pink indeed. It’s not a great color for a hot tub (unless you really like pink). Pink algae is not really algae at all but rather a form of bacteria that acts like algae. 

It is not a common occurrence in hot tubs and not the easiest to remove, so if you do happen to find a pink hot tub in your backyard, it’s important to thoroughly clean and disinfect right away. A strong shock, a brand new filter, and lots of bleach are your weapons of choice for this battle.

Other Colors of the Rainbow

Algae, bacteria, and metal contamination can cause your hot tub to turn all sorts of pretty (and not-so-pretty) colors. The most common are green, yellow, pink, brown, and white. If you notice that the water in your hot tub has chameleon shifted overnight, you can follow the steps above to cleanse and decontaminate.

Algae-Free Is the Life for Me

Now that you’re properly armed with the understanding of how to prevent algae outbreaks and the know-how of how to remove if it does creep in, you can relax and soak worry-free in your clean and bubbly hot tub.

Categories: Hot Tub Care, Hot Tub Problems