Jump Right In
Blog Home How Do You Clean A Green Swimming Pool?

How Do You Clean A Green Swimming Pool?

Categories: How To Guides, Chemicals, Filters, Maintenance & Upkeep, Safety
Yesterday your pool was pristine, the kids were swimming all day and this morning you find the pool green and murky. Like any of us would be, you’re confused and wondering, why is my pool green and what should I do?
This is a very common scenario and the problem is not always easy to resolve. However, if your dedicated to following our three steps outlined below your green pool should be cleaned in no time! Remember, there is no magic elixir, but there are tools and chemicals that will aid you along the way.
Before we get started, it’s important to remember that it is not safe to swim in a green pool. Especially when it is going thru the process of being cleaned up. Your water is not sanitized or balanced properly, and you are more than likely adding chemicals in a strong concentration. Plus, you really need all the help you can get clearing it up and bodies in the water will not do you any good.
1. Check Water Chemistry
The first thing that you need to do is check your water chemistry. If you are a pool owner you should have a good reliable test kit on hand. My recommendation is the Taylor K-2006C as it has a FAS/DPD test. It has easy to understand instructions and is based on droplets of ten. If you can count to ten, you can ace your chemistry every time! In addition to that kit, the AquaChek Phosphate Test and the AquaChek Salt Test if you have a salt water pool should take care of most of your issues. These kits should get you through the season without leaving home unless you have metal, TDS or fill water atrocities. Any test kit that has just two or three reagents for testing chlorine and pH is not going to do you any good.
Writing down your test results will allow you to plan your assault. A notebook with a simple spread sheet with columns for each test and date will do you wonders in understanding your chemistry. Be sure to have a record of what you performed and added to remedy the problem. You will also need to know how many gallons of water are in your pool. You can find a good pool water calculator here.
Take two water samples, one should come from where you fill the pool. Have them both analyzed at your nearest pool store. You will not be able to test for TDS or metals with the kits mentioned above. Be sure to get the results on paper for reference.
*What does TDS stand for and what does it mean? TDS or Total Dissolved Solids is all the “stuff” that is dissolved in your water.
2. Balance Water Chemistry
There are a few basic factors that are necessary to get under control:
  • calcium hardness
  • alkalinity (the waters ability to absorb acid)
  • pH level (how acidic your water is)
If you find that your pool water's chemistry is so out of balance that it's untreatable, you may have to drain your pool.
  • If your water sample's TDS is 1500 ppm over the TDS of the water from your fill location, you should drain your pool.
  • If you have high TDS and calcium levels over 300, you guessed it, drain your pool.
  • If you have high TDS, high calcium readings and cyanuric acid over 50 it’s a no brainer, drain your pool.
If your water contains over 200ppb of phosphates you will need to treat it. I personally like the Orenda line of products - their CV-700 is both a phosphate remover and an enzyme that breaks down organic contaminants. Using a phosphate remover takes away the food that algae thrives on. Our blog post on stopping algae growth before it starts offers more detailed information on phosphates. 
Adjust your pH, alkalinity and possibly your calcium hardness. Adjust hardness first if you need to increase, followed by alkalinity, then pH will fall into place easily after that. You can adjust alkalinity and pH during the day by adding small increments of chemicals over several hours, do not dump a bunch of chemicals all at once into the water. A test for combined chlorine will reveal a total that you can use in the test kit tables to determine your super chlorination dose.
Check out our blog post on balancing your water chemistry for a detailed guide.
3. Clean Your Filter
  • To clean Diatomaceous Earth Filters ( D.E. ) you will need to take the top off and disassemble the filter grids from the manifold. Hosing the muck from the filters with a high pressure nozzle on a garden hose should get you down to the fabric covered grids. A scrub brush or pool brush with a bit of dish soap or Trisodium Phosphate (TSP available at hardware stores) should get you to a respectable level of cleanliness. You should inspect the seams, corners and edges for holes or tears. If your grids are damaged you will need to replace them, failure to do this will result in D.E. coming back into the pool. Rinse the filters well before assembly and recharge your filter with the correct amount of D.E.
  • For Cartridge Filters following the directions above for D.E. filters is recommended. Be advised that with time or many seasons, the cartridges will get plugged with oils. If you cannot get the cartridges to a respectable state of cleanliness you should replace them. I recommend that you have a back-up set of cartridges on hand to minimize down time. Soaking your cartridges overnight with a cartridge cleaner like the ClearView Filter AID or TSP, will help you keep a replacement set on hand. Always rinse your filters well after a soaking.
  • I recommend that Sand Filters be cleaned manually after an algae bloom. Backwashing does not clean filters as well as a manual cleaning. Sand doesn’t wear out, it gets loaded with junk and oils, it channels and gets hard and crusty. If you cannot get the sand clean, replace it. To manually clean your sand filter begin by backwashing the filter until the water to waste comes out clear. Remove the top of the filter. Use a high powered garden hose nozzle to break up clogs of oil and dirty sand, force the nozzle down to the bottom of the filter. You want the sand to move freely in the filter as you scour the sand bed. You will feel this with your fingers as you move through the sand. If your sand is really dirty, soak the sand overnight in a solution of TSP and scour the sand again with the hose before assembly. If you cannot get the sand clean don’t fight it, replace it. When you are finished, put the lid back on and backwash the filter until clear water flows to waste. You should do this especially with new sand.
Your filter needs to have a working pressure gauge on the top. Why, you ask? Your filter picks up debris, body oils, sunscreen, etc. As your filter gets dirty it gets resistant to water flow and as a result the pressure reading will go up. The rule of thumb is, when the pressure is five to eight pounds higher than it was after a cleaning, then it’s time to backwash the filter and / or manually clean. So, once you’ve cleaned your filter, enter the pressure reading into your log book for reference later. Knowing when your filter is getting dirty will help eliminate problems.
If you’re feeling a little lost and would like more detailed instructions on cleaning a filter, check out our blog post on how to clean your filter. Questions about replacing filter grids and cartridges? We have two great articles, one on replacing filter grids and another about replacing filter cartridges.
You can take care of two important tasks in unison. Go ahead and address the chemical issue while you clean your filter. Adding chemicals, especially to adjust alkalinity and pH, can be performed with the pump off. If you need to add acid, add about 20% less than the test kit tells you and use a brush to stir the water. While your chemicals are doing their job, clean your filter. When you finish cleaning your filter, turn on your pump for 24 hours to clear the water.
With a clean filter and your water balanced, you will need to determine if the pool needs another dose of chlorine or if it needs to be super chlorinated. Again, I refer back to a reliable FAS/DPD test kit, it will enable you to determine how much of what chemical to add to your pool with the charts provided.
In closing, I have a few suggestions that I can make when it comes to dealing with pools and spas and avoiding messes like a green swimming pool. First and foremost on the list is routine. We have a great post on developing a maintenance schedule. Set aside a half hour once a week at a minimum. Do not let it go thinking you will catch up to it later. You are maintaining your pool, not overhauling it. Test your water and log the results. Clean your filter when it is needed. The next item would be to invest in a FAS/DPD test kit. I like the Taylor I mentioned earlier, but we carry others as well including test strips.
My next recommendation is investing in a U.V. system or Ozone system. Either of these products will reduce your chemical bill by 50 to 70%. They eliminate chloramines and combined chlorine. Dollar for dollar they save you a ton of money and headaches - they run on pennies per day. The Delta Ultraviolet E-46 and E-57 or Del Ozone EC-10 with an injector manifold will handle a residential pool of 25,000 gallons just fine. If unplugged during the winter, all of these units will last you several seasons.
The last thing on my list is using a phosphate remover and catalytic enzyme. I like the Orenda CV-700, but the Easy Care Algaecide is a bit easier on the pocketbook.
If you need help, we are here for you. Our staff have hands on experience with pools and spas and we are open late evenings and weekends. Give us a call - (888) 836-6025!
comments powered by Disqus
Related Articles
A Guide to Proper Pool Water Chemistry
A Guide to Proper Pool Water Chemistry
Take the fear out of pool chemicals & balance your pool water like a pro with Pool Supply Unlimited’s guide to pool water chemistry. Learn more today!
How to Clean Your Pool Filter
How to Clean Your Pool Filter
If your pump is the heart of your pool or spa the filter is its kidneys. Daily, your filter removes dirt, oil, organic and inorganic substances. Having clean, healthy water is dependent on your filter operating at its peak performance and that is with a clean filter.
Phosphates & Nitrates: Stopping Algae Growth Before It Starts
Phosphates & Nitrates: Stopping Algae Growth Before It Starts
Algae is the arch enemy to many pool owners - Algae can wreak havoc and be very hard for a pool owner to get rid of. In this blog post we get to the root of fighting algae growth - stopping it before it starts by warding off phosphates and nitrates.
Why Is My Pool Green?
Why Is My Pool Green?
In my last post on How to Clean a Green Swimming Pool I addressed the steps to clearing up your pool after your pool turned green. But what you may not know is why your pool is turning green. It is important to know what is causing your water to turn green so you can prevent it in the future. This p...
Pool Supply Unlimited is an e-commerce company that loves water. We love to pump it, filter it, heat it, chlorinate it, light it up and stare at it while we're barbequing a fat, juicy steak. There are real pool professionals working here. Our guys have seen thousands of pools in their careers, no exaggeration. We are based in San Antonio, TX and can land most products to your door (within the 48 contiguous states) in less than a week.
Visa Mastercard Discover American Express