Ready to relax in your hot tub? But wait – what if the water has turned green? Suddenly, your relaxation plans are on hold.

While green water in your hot tub is a common issue, it may likely not be caused by what you think.

People often assume algae is the culprit; however, other common causes are improper pH balance, metals – particularly oxidized copper – or minerals released from the plumbing.

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

Algae: The Slimy Invader

Algae in your hot tub water typically appears due to low sanitizer levels (low levels of chlorine or bromine), poor water filtration, inconsistent hot tub maintenance, organic matter that got into your hot tub – like leaves – or from a swimsuit or spa accessory that was in the water that contained algae – like a lake, river or even someone else’s hot tub.

Here are the signs of algae in your hot tub:

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

• Cloudy Water: The water might appear cloudy or murky along with the green tint.

• 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 hot tub surfaces. Click here to jump straight to algae solutions!

Improper pH Balance

Oxidized Copper: The Sneak

On the other hand, if your water is green and there’s no slimy feel to it, and no foul smell, the cause may be oxidized copper. It can accumulate or exist in your hot tub 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 hot tub 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.

Buildup in the Plumbing

Your hot tub’s plumbing is made up of at least 100 feet of pipe that leads into your hot tub 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 build becomes more and more resistant to any sanitizer.

If your hot tub water is murky, green or cloudy – no matter what you do – it’s highly likely it’s time to purge it.

Fortunately, purging your hot tub isn’t that difficult. Check out our article “How to Purge Your Hot Tub.” Once done, your water will be crystal clear and clean!

Find the Problem

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

1. Observe the Water, Your Hot Tub Surfaces and Filter:

• Check for slimy surfaces – touch the inside of your hot tub walls, if they feel even slightly slimy, algae could be the culprit.

• Cloudy water can also indicate algae.

• Clear water with 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, 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 hot tub dealer for testing. Find your local hot tub dealer here!

How to Fix Green Water in Your Hot Tub

Once you’ve determined what’s causing your hot tub 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:

1. Shock the Water: Use a chlorine or non-chlorine shock treatment to kill the algae. Read the product instructions closely for the correct dosage.

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

3. Filter Maintenance: Algae may clog your hot tub 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.

4. Regular Maintenance: To prevent future algae growth, maintain proper sanitizer levels, clean the filter regularly, keep your cover on your hot tub when it isn’t in use and follow a routine cleaning and purging schedule. Read our article, “When it’s Time to Purge Your Hot Tub” 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, which causes discoloration. Ask your local dealer for recommendations.

2. Drain and Refill your Hot Tub: If copper levels are extremely high, partially draining and refilling the hot tub with fresh water may be necessary. Be sure to balance your water even when draining and refilling your hot tub partially with new water. Use our FREE Water Balancing Guide for help!

3. Check Source Water: Before you fill your hot tub 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.

Prevention Tips

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

• Keep your hot tub covered when not in use: An uncovered hot tub means anything can get into the water. And if your hot tub is outside, the sun will help algae grow!

• Test Your Water Regularly: Not adding enough sanitizer (bromine or chlorine) or not adding it often enough can lead to trouble. Frequently test your hot tub 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 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 hot tub water care routine. Your local dealer can help you with this too!

• Clean Routinely: Give your hot tub surfaces a good cleaning regularly – along with your filter – to prevent the buildup of algae and other contaminants. Oh, and don’t forget to stay on schedule with hot tub drains and refills. Want more information on when and how to purge your hot tub? Click Here!

Relaxation Time

Now that you know the difference between algae and oxidized copper, plus how to address each issue, you can keep your hot tub water crystal clear so it’s ready when you are!

Speaking of maintaining crystal clear water with consistent sanitizer levels, check out FROG^® @ease^®. It’s a complete sanitizer that uses up to 75% less chlorine*, kills bacteria 2 ways and keeps your water Cleaner, Clearer, Softer^® and easier to take care of.

* Compared to the minimum ANSI recommended bromine or chlorine level of 2.0 ppm for a hot tub