Ready to take a swim or soak in your swim spa?

But wait – what if the water has turned green? Suddenly, your plans are on hold. Swim spa water can turn green for a couple of reasons.

While you may assume algae is the culprit, other things can cause your swim spa water to appear green. Common causes can be that the pH is not in balance, or from minerals, or metals – particularly oxidized copper – in the water.

Knowing what’s caused green water and how to correct the problem can save you hours of hassle and get your swim spa time back on track.

4 Green Swim Spa Water Culprits

1. Algae: The Slimy Invader

The most common reason algae will grow in your swim spa water is that sanitizer levels (chlorine or bromine) are too low.

Algae grows if organic matter – like leaves – gets into your swim spa or from a swimsuit or spa accessory that was previously in water that contained algae – like a lake, river or even someone else’s swim spa, pool or hot tub.

Additionally, algae could be due to  poor water filtration or inconsistent maintenance,

Algae is insidious – you often cannot see the teeny tiny spores, that’s why it’s essential to rinse swimsuits thoroughly in tap water, clean every accessory that comes near your swim spa water, and keep filters clean and replaced as needed – more on this to come!.

Then again, if your swim spa water looks green, it may not be algae. Here are the signs of algae in your swim spa:

• Slimy Texture: The water may feel slick or slippery, and you might notice or feel slimy patches on the swim spa walls, seats or floor.

• Cloudy Water: Along with the green tint, the water might appear cloudy or murky.

• Musty Odor: Algae can cause a musty or unpleasant smell.

If you suspect algae, it’s crucial to act quickly. Left untreated, algae will continue to grow and can damage your swim spa surfaces. Click here for algae solutions!

2. Improper pH Balance

If pH is off, your sanitizer won’t work effectively. That means the sanitizer can’t do its job properly, and algae can get a start. A small amount of algae will grow. And grow. It won’t go away unless you take specific action.

Test your swim spa water to determine whether or not the pH is within the ideal parameters.

Ideal pH balance for swim spas: 7.2 – 7.6

If it’s not within these parameters, adjust accordingly. For extra help to balance your swim spa water, check out our Water Balancing Guide for Swim Spas.

3. Oxidized Copper: The Sneak

On the other hand, if your water is green and there’s no slimy feel to it or to its surfaces, and there’s no foul smell, the cause may be oxidized copper.

How can copper get into your swim spa water? Good question! It can exist or accumulate in your swim spa due to:

• High Copper Content in Source Water: If your fill water contains a high copper content, it can oxidize and cause the water to turn green.

• Copper Component Erosion: If your swim spa has copper pipes or heating elements, corrosion over time can release copper into the water.

• Copper-based Algaecides: While these products effectively prevent algae, they can increase copper levels in the water.

4. Buildup in the Plumbing

Your swim spa’s plumbing is made up of over 100 feet of pipe that leads into your swim spa to fill it with luxurious hot water and shoot out jet streams that help you relax and unwind.

Unfortunately, the pipes can build up with microorganisms, which eventually turn into biofilm. Biofilm buildup becomes more and more resistant to any sanitizer.

If your swim spa water is murky, green or cloudy – no matter what you do – or if you add sanitizer and it doesn’t register on your test strip or “do” anything, it’s highly likely it’s time to purge it.

Fortunately, purging your swim spa isn’t that difficult. Check our article “How to Purge Your Swim Spa.” Once done, your water will be crystal clear and clean!

Additionally, routine purging is good maintenance to ensure water stays clean and clear and that your sanitizer continues to work well, so your swim spa is ready when you are.

How to Find the Problem

Follow these steps to determine what is causing your water’s green tint:

1. Observe the Water, your swim spa surfaces and filter:

• Check for slimy surfaces. Touch the inside of your swim spa walls, if they feel even slightly slimy, algae could be the culprit.

• Cloudy water can also indicate algae.

• Clear water that appears green but has no slime points toward oxidized copper.

• Hard-to-manage water could indicate biofilm buildup. If you test your water and it’s within ideal levels or if you add chlorine and still don’t get clean, clear water, biofilm may be the problem.

• Check your filters: If they’re old, worn, or dirty, they could be the cause of poor water quality.

2. Water Testing:

• Check your water’s copper content with a water test kit. High readings suggest that copper is the culprit.

• Or, bring a water sample to your local swim spa retailer for testing. Find your local swim spa retailer here!

How To Fix Green Swim Spa Water

Once you’ve determined what’s causing your swim spa water to be green, cloudy, slimy or smelly, you can correct it without trial and error.

How to Treat Algae

If algae is the problem:

• Shock the Water: Use a chlorine or non-chlorine shock treatment to kill the algae. Read the product instructions closely for the correct dosage. FROG Maintain^® for Swim Spas in a one-dose packet is an easy, effective solution.

• Brush and Clean: Give your swim spa walls and floor a good scrub to remove every bit of algae clinging to the swim spa insides and surfaces – including the cover, inside and out.

• Filter Maintenance: Algae may clog your swim spa filter. If your filter builds up with algae, it can’t do its job, then you get green water. Clean or replace the filter cartridge regularly, following the manufacturer’s directions to ensure it works properly.

• Regular Maintenance: To prevent future algae growth.

• • Test your swim spa water a minimum of once a week – or more – and adjust as needed to Maintain proper sanitizer levels

  • Clean the filter regularly

  • Keep the cover on your swim spa when it isn’t in use

  • Follow a routine cleaning and purging schedule.

Read our article, “When it’s Time to Purge Your Swim Spa”  for more information!

How to Remove Oxidized Copper

Follow these steps to correct oxidized copper in your water:

1. Metal Sequestering Agent:

Add a metal sequestrant to the water. It binds with the copper and stops it from oxidizing. Ask your local retailer for recommendations.

2. Drain and Refill your Swim Spa:

If copper levels are extremely high, partially draining and refilling the swim spa with fresh water may be necessary.

Be sure to test and balance your water when draining and refilling your swim spa partially with new water.

Adding source water to refill it can cause the Total Alkalinity, pH or Total Hardness levels to go out of balance.

Use our FREE Water Balancing Guide for help!

3. Check Source Water:

Before you fill your swim spa with fresh water, test your source water for copper content. You can do this yourself with a water test kit or ask your dealer for help. If the copper reading is high, you’ll want to add a hose filter to filter out excessive metals.

4. Maintenance Routine:

Regularly test and balance Total Alkalinity, pH and Total Hardness to prevent metal problems. Avoid using copper-based algaecides if your source water already contains high levels of copper; ask your local retailer for recommendations. They are probably well-versed in local water sources and can best help you.

Prevention Tips

Keeping algae out, maintaining ideal water balance levels and managing the copper content in your water is much easier than correcting problems. Plus, you won’t be unpleasantly surprised when you’re ready to swim or soak in your swim spa and find the water is not ready for you.

Put these tips into practice, so your swim spa is ready when you are:

Keep Your Swim Spa Covered When Not in Use:

An uncovered swim spa means anything can get into the water. Plus, with an outdoor swim spa, the sun will not only help algae grow, but UV rays also burn off chlorine or bromine very quickly!

Maintain Sanitizer Levels

Not adding enough sanitizer (bromine or chlorine) or not adding it often enough can lead to trouble. If algae is in the water, chlorine will fight it; that takes chlorine away from killing bacteria and leaves your swim spa water not sanitized properly.

Frequently test your swim spa water to maintain proper water balance. Balanced Water means that free chlorine, Total Alkalinity, pH and Total Hardness are within ideal levels. Testing your water consistently will help prevent numerous problems and catch issues early.

Use High Quality Chemicals:

This includes sanitizers, algaecides and metal sequestrants, all of which help keep your water clean and clear. Invest in quality chemicals for a good swim spa water care routine. Your local retailer can help you with this too!

Clean Routinely:

Regularly give your swim spa surfaces a good cleaning – along with your filter – to prevent the buildup of algae and other contaminants. Oh, and remember to stay on schedule with swim spa drains, refills and purging. Want more information on when and how to purge your swim spa? Click Here! 

Exercise or Relaxation Time

Now you know what’s causing your swim spa water to appear green. And the difference between green water due to algae or oxidized copper – plus how to address each issue. Even better, you can keep your swim spa water crystal clear so it’s ready when you are!

Speaking of maintaining crystal clear, clean water that’s ready when you are, you may want to check out FROG^® @ease^® Sanitizing System for Swim Spas.  It’s the only complete sanitizer for swim spas!

FROG @ease

• Uses up to 75% less chlorine*

• Kills bacteria 2 ways

• Keeps sanitizer levels consistent at all times

• Keeps your water Cleaner, Clearer, Softer^®

• Makes taking care of swim spa water much easier

What’s more, you don’t to have add sanitizer daily or even after every use, just once a month!. You gotta love that!

Questions? Call our Customer Service Department at 800-222-0169 Mon-Fri 8 am – 5 pm CST, email customer.service@kingtechnology.com or ask a question on the Ask FROG^® Chat box on the FROG website.

*Compared to the minimum ANSI recommended bromine or chlorine level of 2.0 ppm for a swim spa.