Green Pool Recovery: A 12-Step Guide

Around the world, green is the second most popular color, but in the world of pool owners, green is Public Enemy #1. When you’ve returned from being out of town and [Insert Dramatic Music] you’re greeted by a green pool, what do you do? What should you do? There are a variety of approaches commonly offered up, with some being valid, others incomplete, and some just flat out wrong. So while there’s more than one way to vanquish the green, we will share our way to get the job done.

Preparation

The first thing to do is remove all plant matter and other debris from the pool, particularly in the aftermath of a storm. Next, inspect your filtration system, paying particular attention to the pressure reading. Your filter is about to get a serious workout, so if your filter pressure is already high, go ahead and backwash the system or clean your cartridge(s), as appropriate.

Tip: Take note of your filter pressure when clean. Write it down if your memory is like mine!

Test your water and determine where you stand relative to target levels. Rebalance the water to target levels as detailed in the following chart. Pay particular attention to the Total Alkalinity (TA) and pH. The pH level is critical with regard to the effectiveness of Chlorine and the TA level influences the pH.

Target Water Chemistry

If your Cyanuric Acid (CYA or Stabilizer) is over 50 ppm, then this is the ideal time to drain enough water to bring the level down to 50 or less, but no lower than 30. If you simply can’t replace that much water, it is vital that the CYA level is brought down to no more than 70. If the local pool store or your “pool guy” says otherwise, they’re simply behind the times on this subject.

Process: The Name is Shock. Chlorine Shock.

My dictionary says that “Algaecide” is “an agent used to kill algae.” From that standpoint, Chlorine Shock is the most effective algaecide available and has a license to kill algae. Other non-Chlorine products commonly referred to as “Algaecide” can also kill algae, but Chlorine is more effective in killing algae while these Algaecides are better suited to prevention.

So, we’re using Shock instead of Algaecide in order to quickly kill off the algae multiplying in the pool. Which shock? The short answer is Liquid Chlorine (Sodium Hypochlorite), aka Bleach. Liquid Chlorine won’t add Calcium to the pool’s water and is non-stabilized, so it won’t raise your CYA level.

However, Liquid Chlorine raises your pH and it has a short shelf life. Only buy what you can use within a couple of months to offset the 50% drop in potency after 6 months and the 90% drop after a year. You should also be cautious about the age of the product straight off the shelf.

Safety Note: Take all precautions noted on the label. ALWAYS pour Liquid Chlorine into water. NEVER add water to Liquid Chlorine.

Add sufficient Liquid Chlorine to bring the Free Chlorine level to an estimated 30 ppm. If you are using the commonly available 12.5% Liquid Chlorine, this is about 2 gallons per 10,000 gallons of pool water.

Tip: Add your liquid chlorine at dusk or carefully add it around the entire pool in order to either avoid sun exposure or to allow time for the liquid chlorine to disperse throughout the pool.

Although the shock you’ve added will handle the lion’s share of sanitizing your pool, your Salt Chlorinator can pitch in as well, operating on its usual setting. Turning the Salt Chlorinator up or using a Superchlorinate setting is not necessary due to the large dose of shock you’ve just used.

Cleanup

Until the pool is back in shape, you should let your pump run continuously to filter the water. On a daily basis, it is important to monitor the filter pressure for changes. If/when the filter pressure begins to show 8-10 lbs over the baseline, it is time to backwash/clean your filter again.

Brush all your pool surfaces, giving special attention to anywhere you see algae. As the process continues, repeat brushing periodically to break loose any remaining algae.

Testing

You started this process by balancing aspects of the water chemistry, particularly the pH and Total Alkalinity, but they won't stay on target. In order to optimize the effectiveness of the chlorine (Shock), it's vital to keep these numbers on target. Consequently, daily testing will allow you to intervene as often as necessary to keep the Chlorine at peak efficiency.

Once the Free Chlorine level declines to 5 ppm, evaluate the condition of pool surfaces and the water itself.

• Is your Combined Chlorine below 0.1 ppm?
• Is the water colorless and the pool surfaces clean?

If that’s a “yes” to all three, then you can return to business as usual with respect to circulation and chlorination. If the water or the surfaces still retain any green or the Combined Chlorine hasn’t been oxidized, then rebalance the water and shock the pool again.

Prevention

Are We There Yet?

All too many pool owners reach this point, breathe a sigh of relief, and return to their usual routine. Unfortunately, the process is not complete. The organisms we’ve just killed all grew fat on phosphates. Not only does your pool still harbor any phosphates that were fueling the algae bloom you just knocked out, but when algae dies it releases more phosphates back into the water too.

Consequently, there’s one more vital step to take. Treat your pool with a Phosphate Remover, carefully following the product’s instructions. In particular, be sure to clean/backwash your filter (usually) two days after adding the phosphate remover. Phosphate removers interact with the phosphates allowing the filter system to capture them. However, the filter still needs to be cleaned/backwashed in order to remove the phosphates from the pool.

Use a dedicated-purpose phosphate remover such as Orenda PR-10000. Avoid using multi-purpose products which contain a phosphate remover designed to be added routinely, often weekly. Our goal is to remove phosphates from the water, not to simply suppress them over time.

Phosphate issues are common, but testing for them is routine and products that remove them are widely available. An intractable problem with high chlorine demand might be caused by nitrates in the water. If all else has failed, track down test strips that can detect nitrates. If they are identified as a problem, you will need to reduce them by drawing down the pool level and adding water.

Let’s (Try) Not To Do This Again

Purging the pool of phosphates is a pivotal part of prevention, but there’s more that can be done to avoid algal blooms. With the potential for algae always with us, it’s vital to always have “your shields up.” Central to this is the idea that you should always maintain a Free Chlorine level of 1-3 ppm.

Equipment Efficiency

Two key components of modern, efficient pool management are Salt Chlorinators and Variable Speed Pumps (VSPs); both facilitate best practices in preventing algae. Your VSP allows you to significantly extend your daily circulation and filtration time. You can maintain circulation around the clock and still save significantly on your power bill. Remember, still water is algae’s friend.

If you have elected to extend the filtration and circulation of the water, turn down your Salt Chlorinator and let it add that same daily chlorine to the water throughout more of the day. The longer your Salt Chlorinator is not generating chlorine, the higher the chlorine level needs to be in order to last until the next day—algae never sleeps.

Narrowing the pH Range

Next is your pH which is critical to the potency of your chlorine. The only thing better than keeping your pH “in range,” is to narrow that range too. In other words, to aim for a “target” of 7.5. Instead of regular testing and rebalancing your pH between 7.2-7.8, go ahead and focus on keeping it between 7.4-7.6 instead. Admittedly, this does mean more testing and more time adjusting pH, but modern technology has given us a way to not only keep our pH on target, but to do it without acid, and to do it automatically.

Borates and Sanitation Boosters

Another means of staying on top of your pH and preventing algae is to introduce Borates into your pool water. As a “buffer” which resists increases in your pH, Borates assist in optimizing the effectiveness of your Chlorine. In addition, Borates act as an Algestat inhibiting algae by disrupting its growth.

You may want to readdress the adequacy of your sanitation system. If the system isn’t rated for 1.5-2 times the pool size or more, it will struggle under peak conditions leaving you prone to an algal bloom. If your system is undersized, investigate whether it can support a higher capacity Salt Cell or explore supplementing with Ozone or Ultraviolet (UV) sanitation. Any of these three steps can give you that extra boost in capacity that allows you to reliably maintain a safe reserve of 1-3 ppm Free Chlorine.

Everything we’ve discussed so far is generally sufficient to keep your pool free of algae. However, as an added layer of protection, now is when you can consider using an Algaecide to help prevent any future outbreaks.

So, there you have it. Green things happen to good pools, but if you follow our plan, we’ll have you safely swimming in a crystal clean pool in very short order.