Green Water in Your Hot Tub – How to Fix it the Easy Way

After a long time, you’ve finally found a day off where you intend to spend your me time lounging about in your spa. Except that what awaits you is not the sight of clear water that you can just submerge yourself in, but an icky green that’s not just a reflection of the light.

Your hot tub water is now green and no, that isn’t normal!

The bad news? Your hot tub has algae. The good news? It’s completely treatable and though labor intensive, completely worth it. The best news? You can easily prevent this with a few smart precautions.

It is easy enough to get rid of green water in your hot tub when you know how. Read on to know how to solve your hot-water-tub woes!

how to fix green water in your hot tub

But Why Is My Tub Water Green?

Why is your tub green instead of blue, you wonder? A range of reasons could have contributed to your spa’s now-green nature, such as:

  • Inadequate sanitization or over-sanitization, or irregular sanitization.
  • Algae moving homes from an algae-infested pool or water body that you probably visited earlier to your spa; your swimsuit or any accessory that you used in said pool will serve as the mode of transport for said algae!
  • Defective filtration system.
  • Insufficient cleaning and replacement of the hot tub’s filtration system.
  • Leaving the hot tub uncovered when not in use; an outdoor spa is especially conducive to green algae growth, thanks to the added sunlight factor (this is, by far, the most common reason for green hot-tub water).

Why is it important to know why your hot tub water is green?

Well, because prevention is better than cure and knowledge of what causes something leads to prevention. Hot tubs can suffer from a range of problems – here at Outdoor Care Guides we cover the most common ones and how to fix them:

Now that you know why your spa could turn green, look to these steps to prevent algal bloom growth, as well as the following.

Getting Rid of Algae in Your Hot Tub

As mentioned earlier, getting rid of algae in your tub can be a little back breaking and sweat inducing, but hey, no pain, no gain! Unfortunately, there are no shortcuts to success, especially with a green tub in the picture, so set aside a Sunday and do the following!

Spa Deep Cleaning

Though a spa should generally give you a good deep cleaning, sometimes, you may have to give your spa a good deep cleaning. To do this, drain the hot tub and clean it thoroughly. Get rid of every bit of water in the tub and scrub down the surfaces to ensure that the algae has completely disappeared from all parts of the tub.

Clean and / or Replace the Filter

Unfortunately, just rinsing your hot tub and the filter in clean water won’t get rid of your algae woes – you’ll need to thoroughly clean the filter by applying a filter cleaner. You can even soak the filter overnight in a chemical rinse to be doubly sure that the algae is gone.

If the filter is worn out (or even an overnight chemical soak doesn’t do the trick for you), replace it.

Scrub That Tub!

To completely and thoroughly get rid of the algae, you’ll need to scrub down your tub. You could use diluted bleach, diluted cleaning vinegar, or even any other household cleaning product to get the job done.

If you want to get the job done, though, use a cleaning agent made specifically for hot-tub cleaning, such as this one – Oh Yuk Healthy Hot Tub Cleaner.

Refill Your Tub

Refill your tub, but remember, whether you refill it with well water or city water, using a hose filter is prudent. This keeps out any contaminants and minerals. The ‘Camco Hose Filter’ comes highly recommended.

Clean the Spa Cover

It isn’t only important to scrub out your tub, but the tub cover as well. Condensation will collect on the cover’s underside, creating a habitat conducive for algal spore growth.

Since you’ll anyway be waiting for the tub to fill up, spend the time cleaning the cover with diluted cleaning vinegar, diluted bleach or a vinyl cleaner, instead of twiddling your thumbs! Again, you might want to use a cleaner built specifically for hot tub cleaning, like the 303 Products Multi-Surface Cleaner.

303 Marine Multi-Surface Cleaner
Safely Cleans All Water Safe Surfaces, Including All Types of Fabric and Vinyl, Rinses Residue Free, Manufacturer Recommended, 32oz

Shocking the Water

Like a pool shock, shock your hot tub too. Shocking involves the addition of chlorine or non-chlorine chemicals to the water to prevent any bacteria and algal growth. Give your tub a good shock to keep the algae at bay. The ‘Spa Essentials Dichlor Chlorine’ is a good call.

Spa Essentials Xtra Chlorine Shock (6 lb)
SPARKLY SPA: Restore your spa’s sparkle with this extra-strong shock treatment. REMOVES ODORS: Easily removes unpleasant odors and adds clarity to the water. WORKS WITH: Uses dichlor chlorine that’s compatible with chlorine, brome, and ozone

Testing the Waters

Quite literally, it’s time to test the waters! Once the shock has “worn off”, test the water with a liquid test kit or test strips – the AquaChek Select Spa Test Strips are pretty efficient and get the job done well. With a testing strip, you can test for total chlorine, bromine, free chlorine, pH, alkalinity, cyanuric acid and hardness levels.

See my guide on testing your hot tub water to learn how to do this quickly and accurately.

Balancing the Water

After the chemicals that you’ve added in have had the time to dissolve and disperse, test the water again. If the figures are off, you’ll need to add them again to get the balance right and repeat this entire step again or as many times as required, till the right balance is achieved.

Yellow Water in Your Hot Tub?

Don’t worry if the water has turned yellow – it’s not an additional problem to deal with, but it’s still likely a part of the same problem! Yellow water means that you still have an algae problem, but of a different kind – your tub has been afflicted with mustard algae, quite rare in areas with a cold climate.

Unfortunately, getting rid of yellow algae takes even more work than getting rid of green algae. To make it even worse, such algae are even known to be resistant to chlorine.

Don’t give up heart, though. Follow the same cleaning steps listed above and persist!

How to Prevent Algae In Your Hot Tub

There are many small but effective things that you can do to prevent algal blooms in your hot tub. Some of these include:

  • Cover your hot tub at all times when it’s not in use, even if it’s an indoor tub.
  • Regularly check the filtration system for damage or defects. This way, you can replace any worn-out filters in a timely manner.

Clean the filtration system regularly.

If you’ve used your swimsuit or swimming accessories in a pool or tub other than yours, wash them before you get into your pool or tub. This prevents the risk of any algae hitching rides on your clothes and accessories.

Ensure that you add sufficient amounts of sanitizer to your hot tub – base this on the volume of the tub. Additionally, add sanitizer in the regular intervals that you’re supposed to add it in – you can keep a check on this by testing the water regularly.

Consider using some of these alternative hot tub sanitizers to get your water quality just how you like it.

The Bottom Line

If you’re wondering whether all the effort truly keeps away the algae once and for all, the answer is – you can never know! Both green and yellow algae are incredibly hardy and needing two or even three tries, to completely get rid of these, is quite common. Tough luck, but necessary.

Therefore, to save yourself a world of pain and work, take the necessary precautions, keep your tub clean and the water balanced and you’ll greatly reduce the risk of a 28 Days Later scenario a la ‘le algae’!

Last update on 2023-02-06 / Affiliate links / Images from Amazon Product Advertising API

michael keenan author

Author - Michael Keenan

I'm Michael Keenan the owner and creator of the Outdoor Care Guide. I'm a trained horticulturist with over 30 years experience in pool care, plant care and landscape care! Seemed like a good idea to share - I think I can make your life easier and save you some time and money!