The Orenda Green Pool Cleanup
Based on 10,000 gallons (37,855 Liters)
Normally, when a pool turns completely green from algae, it has been neglected for several weeks or more. There are usually leaves and other debris piled up in it, and the pool flipped because the pool became eutrophied. Algae takes over a pool when its growth/reproduction rate exceeds the killing rate of the sanitizer (chlorine). You can kill algae with chlorine and algaecide all you want, but unless you address the source of the problem, you could face algae again in the near future. And be aware, most algaecides leave behind byproducts that chlorine will oxidize, so for this procedure, non-stabilized chlorine is the only algaecide used.
The Orenda Green Pool Cleanup procedure is our method of clearing a green pool efficiently. This procedure is a chemical 1-2 punch of non-stabilized chlorine to kill algae, and Orenda chemicals to handle the non-living byproducts. To be clear, Orenda products are not algaecides or sanitizers; chlorine does the killing.
Related: How to Implement the Orenda Program
You will need:
- A reliable test kit with acid demand test (green pool usually have a very high pH)
- Muriatic acid, a clean bucket, measuring cup, and safety gloves/glasses.
- A pool brush, net, and vacuum
- Non-stabilized chlorine (liquid sodium hypochlorite, or cal hypo granular shock)
- Purge dose (32 fl.oz./10,000 gallons) of PR-10,000 phosphate remover
- Purge dose (32 fl.oz./10,000 gallons) of CV-600 or CV-700 enzymes
- Clean out as much debris and dirt as possible with a net and vacuum. Do not shortcut this step! Piles of leaves and debris will protect algae from chlorine and this procedure may not work as well as it should.
- Brush the pool thoroughly.
- Lower pH to 7.4 with pre-diluted acid around the perimeter of the pool.1
- The pH of a green pool can be very high. We have measured it over 10.3 before. See footnotes below.
- Raise chlorine up to 10-15 ppm using non-stabilized chlorine (liquid chlorine or granular cal hypo shock).
- Purge with PR-10,000 phosphate remover (32 fl.oz./10,000 gal) around the perimeter of the pool.2
- Purge with CV-600 or CV-700 enzymes (32 fl.oz./10,000 gal) around the perimeter of the pool or into the skimmer or gutter for faster circulation.
Remove debris and brush the walls and floor to stir everything up. Lowering pH allows for more optimal chlorination (see footnote 1 below), and chemical efficiency is key to this process. The full purge of PR-10,000 eliminates phosphates on contact, which will floc to the bottom. CV-600/700 enzymes attack non-living organics and oils, which there is an abundance of in a green pool.
The water should have cleared up and you should see white dust and dead algae and debris on the bottom of the pool. If the water is still cloudy, consider these troubleshooting options:
- If the cloudiness is light/white/gray colored, it could be calcium precipitating because the pH was not lowered enough. Do an acid demand test to lower pH to 7.4, pre-dilute the required acid, and pour around the perimeter of the pool.
- If the cloudiness is green/brown/murky, there is probably debris that has protected algae in the depths of the pool, and Step 1 on Day 1 was not as thorough as it needed to be. Clean more debris out and repeat the Day 1 process.
If the water has mostly cleared, as expected, proceed with the following steps:
- Thoroughly vacuum the pool (to waste) and skim off any leaves or debris.
- Clean the filter(s). For sand filters, backwash and rinse thoroughly. Consider a filter purge if needed.
- Test the free chlorine level. If you have below 5 ppm FAC, increase chlorine to 5 ppm.
- Adjust the pH and/or alkalinity to achieve LSI balance. The pH will naturally rise, so if you have too low of a pH, let it rise on its own and focus on alkalinity.
Follow Up and Weekly Maintenance
- Perform necessary vacuuming and brushing
- Backwash and/or clean filter as needed
- Make any necessary chemical adjustments
- To be proactive in preventing algae in the future, avoid CYA over-stabilization so that chlorine's killing rate is optimal (Pillar 4), and supplement chlorine to address the oxidant demand from nonliving organics (Pillar 2). Remove phosphates regularly to keep phosphates to a minimum, ideally below 500 ppb (Pillar 3).
1 The pH of a green pool is usually very high due to algae's consumption of CO2. If there is CYA in the pool, pH does not really control the strength of chlorine, and chlorine almost instantaneously binds to CYA. For a green pool, we want the chlorine level to be 10-15 ppm, and we want chlorine working as efficiently and as fast as possible. The other reason for dropping pH prior to chlorine shocking is because hypochlorite chlorines (liquid and cal hypo) have a high pH as it is. When they are added to water, they will create a high-LSI violation locally, and calcium carbonate will precipitate and cloud the water. In the case of cal hypo, the calcium will separate from the chlorine and stay near the surface, turning the water white. We learned this the hard way. Lower pH before shocking.
2 Note: This purge dose is 4x more than the normal PR-10,000 purge dose. Do not swim until the pool is cleared.