Green looks good on trees and grass but when you have green hot tub water it’s a sign you have algae or something is wrong with the water chemistry. Hot tub water must be clean and sparkling clear at all times so don’t accept anything less.
Most green hot tub water is caused poor sanitation resulting in algae in the water. Metal ions like copper can also make water turn green. When the water only has a slight green color you can try to shock the water to kill the algae. If the water is very green I recommend to change the water and don’t waste your time trying to add extra chemicals to water that is already saturated with algae and other contaminants.
Table of Contents
What Causes Green Hot Tub Water
1. Algae
The most common cause of green hot tub water is an algal bloom.
Algae spores have entered the tub and have exploded into bloom under the right conditions of warm water, light and low chlorine (or bromine) levels. The low level of sanitation may be caused by an equipment failure, incorrect equipment settings or you just forgot to put sanitizer in the hot tub.
Feel the sides of the tub or spa pool. Is it slimy and green? This is algae.
If it’s not slimy and green. The cause is bacteria or minerals like copper or manganese in the water.
How did the algae get in your hot tub?
Algae can blow into a hot tub on the wind. It can attach itself to swimwear from lakes and ponds or other swimming pools. Algae can grow on pool cleaning equipment or pool toys so clean everything.
2. Poor Filtration
When the spa filtration system is not functioning properly or you have dirty filter elements this will cause the water to accumulate dirt and algal spores.
3. Metal Ions
Water from dams, wells, ponds, rainwater tanks, copper plumbing or water heaters with copper heating elements can contain copper ions. These ions can cause the water to suddenly turn green.
You can add a liquid metal sequester to the hot tub to remove the metal ions.
What Causes Yellow Hot Tub Water
Yellow hot tub water is most commonly caused by yellow algae.
This type of algae is very difficult to eliminate from a hot tub. Yellow algae resists sanitation chemicals and requires multiple shock treatments to kill it.
I recommend you drain and thoroughly clean the tub and plumbing before refilling with fresh water.
Other Colors of Hot Tub Water
Hot tub water can change to many other colors like pink, brown or white. Whatever the color you need to drain and thoroughly clean the tub and plumbing before refilling with fresh water.
How to Get Rid of Green Hot Tub Water
1. Shock the Hot Tub Water
When the water only has a slight green color you can try to shock the water. If the water is very green you will need to drain and clean the hot tub.
Don’t use the hot tub until the next day as the chlorine level will be too high for bathing after shock treating the water.
You don’t need to add much shock to a hot tub. Many people add too much shock to their hot tub and make the water cloudy. A hot tub only has a small volume of water not like a swimming pool.
Please follow the manufacturer’s instructions for the correct amount of shock for your size hot tub.
2. Drain, Clean and Refill Your Hot Tub
Hot tubs contain a relatively small body of water that can quickly become contaminated even with sanitation chemicals.
When hot tub water is really green I recommend to change the water and don’t waste your time trying to add extra chemicals to water that is already saturated with algae and contaminants.
Draining the water is easy.
The important part is to properly clean your hot tub including flushing the plumbing and filters. Otherwise it’s all a complete waste of time as the bacteria or algae will still be living inside the hot tub plumbing pipes. If you don’t clean the plumbing the same problem will keep recurring every time you refill the tub.
The frequency that you change the water depends on the level of usage of the hot tub. Usually, I recommend to change the water every quarter (3 months). If you are not using the tub at all then there is less need to change the water.
When the hot tub has high usage from many people the water will quickly become contaminated with sweat, skin flakes, hair, body oil and many other substances. The only way to properly sanitize a hot tub is to add more chlorine or bromine. After a while the small volume of water in a hot tub becomes too dirty and contaminated to sanitize with chemicals. The only option to clean the water is to drain and refill the hot tub.
Please read our article on How to Drain & Clean Your Hot Tub
How to Avoid Green Hot Tub Water
1. Regularly Test and Balance the Water
Spas and hot tubs need to be tested every week to ensure the water chemistry is balanced and adequately sanitized. Test the water with test strips which are very accurate these days. Please ensure you have the correct test strips for your type of sanitation chemicals.
Normal levels for hot tubs:
- pH: 7.4 to 7.6
- Chlorine: 1 to 3 ppm
- Alkalinity: 80 to 120 ppm
- Calcium Hardness: 150 to 250 ppm
2. Shock the Water Regularly
When you are using your hot tub shock it once a week.
When you shock a tub with chlorine-based shock you need to wait until the next day before it is safe to use the hot tub. The chlorine level must be below 5ppm otherwise it will irritate your skin, lungs and eyes.
When you shock a hot tub with non-chlorine based shock run the pump and circulate the water for 20 minutes before getting in the water. Non-chlorine based shock is less effective and reactive than chlorine but much gentler on your skin and eyes.
Always read the instructions on the container or packet before adding shock chemicals to a hot tub. Only add a very small amount of shock. If you have added too little you can always add more. But if you add too much you will need to wait several days for the chlorine level to reduce to below 5ppm before you can safely get in the water.
3. Cover Your Hot Tub
A hot tub cover is essential to keep the water clean from dirt and prevent water evaporation. It also prevents young children finding their way into the water.
However, you need to regularly open your hot tub to allow the water to get fresh air.
4. Wash the Hot Tub Cover
Regularly clean the underside of the hot tub cover to remove contaminants. There’s no point to cleaning your hot tub only to put a dirty lid over the top of it.
5. Clean the Hot Tub Filter
It’s recommended to clean the filter element every month or more frequently with high usage. The element is normally fitted under the skimmer basket and needs to be hosed over the lawn to remove dirt and debris.
Many hot tub owners don’t clean the water filter enough. Once the filter element becomes soiled with dirt and other contaminants from the pool water the pressure within the filter system will increase indicating that it is harder for the pump to push the water through the filter element.
When the pressure within the filter system increases beyond a certain level it is time to open the filter and manually clean the element. When a hot tub or spa pool is regularly in use the filter will need to be cleaned every two weeks.
If you frequently clean the element it will never become very dirty and will last much longer before needing replacement.
If the filter element is very dirty you can soak it in a bucket of water with a small amount of vinegar or bleach in the water.
6. Replace the Hot Tub Filter
Normally, a spa or hot tub filter cartridge should be replaced every two years but may need to be replaced sooner with heavy usage.
If the filter element becomes damaged in any way you will need to replace it. Filter elements are relatively inexpensive compared to other pool and spa components so replacing it is not an issue.
7. Shower before Soaking in the Hot Tub
Do you want to soak in dirty water?
Whether you are aware of it or not, your body is covered with organic matter and contaminants. Humans perspire sweat on to our skin which dries and begins to break down. It’s called body odor and smells very bad. Our skin in flaking off our bodies. Our hair is constantly falling out and not just the hair on our heads. Bacteria and microbes are crawling all over our bodies.
Women may also be wearing hair spray, hand cream, moisturizer and perfume.
If you don’t shower before you soak in a hot tub all the dirt and contaminants on your body will wash off in the water. The hot tub water may look clean but it may actually be full of contaminants.
You should always shower before entering any swimming pool or hot tub.
For more information read our article Should You Shower Before You Swim?
8. Rinse Your Swimwear
Rinse your swimwear in fresh water after swimming in a pool or soaking in a hot tub to remove salt and chemicals. The next time you enter the water your swimwear will not contain any hidden chemicals or algae spores.
9. Change to Salt Water Chlorination
Saltwater hot tubs and spa pools are a great solution to reducing the amount of chemicals and the cost of running a spa. Saltwater chlorination is a lot milder on your body because the concentration of chlorine is lower and more stable than in a freshwater spa. There is usually no chlorine smell and the salinity is so low you won’t normally detect it.
Saltwater sanitization prevents foaming, chemical residues, and requires less draining and cleaning of the hot tub.
Saltwater chlorinator units can be attached to the spa filtration unit after the heater to generate chlorine into the water before the water is returned to the spa.
There are also chlorinator units that can be attached to the side of the spa or tub that simply plug into the power supply. These units hang over the side of the spa and require no extra plumbing.
The chlorinator unit uses a low voltage current to split the salt into chlorine which will add a small extra cost to your power bill. However, using a chlorinator means you don’t have to buy chlorine and some other chemicals for the pool saving you money.
Spa pools and hot tubs still need to be shocked with extra chlorine after heavy use or topping up with extra water. The shock process ensures all bacteria and other contaminants are destroyed to make the spa safe for you and your family.
10. Change You Sanitizer
If you feel your sanitizer is not working for you change to a different system.
Biguanide is a water chemistry system that can be used instead of chlorine or bromine. It is more expensive and you still have to add lots of chemical to the spa. You also still have to shock the spa but it’s supposed to be gentler on your skin and hair. Usually you would only use this if you have sensitivity to chlorine or bromine.
Installing an ozonizer is another option where the water is treated with ozone gas to kill bacteria and other contaminants. This is a more expensive option and normally only considered when you have sensitivity to chlorine or bromine.
Conclusion
You purchased your hot tub for your enjoyment and to relax in hot water to gain some of the many benefits for your health and wellbeing. Don’t let green hot tub water spoil your fun. Follow our advice about to always keep your spa in ready-to-go condition.
Regularly draining and cleaning is a simple activity that is essential to ensuring you continue to enjoy a clean and healthy spa experience.
Please read our other articles to help you with all your swimming pool and hot tub problems. If you have a question or comment leave it below in our comment section.