How to Clean a Green Pool in 6 Easy Steps
As a pool owner, nothing is worse than heading out for a swim in the backyard and finding that your pool has turned a mucky shade of green!
If you can’t see the bottom of your pool because of some floating green mystery gunk, your fun in the sun is probably not going as planned.
But hey—no need to ditch your summer plans just yet.
Why Is Your Pool Green?
Before we dive into (pun intended) the how of getting that pool back to blue, let’s take a look at why it turned green in the first place.
In most cases, a pool will become green because of an overgrowth of algae, but the causes for this overgrowth can vary.
The main ones are:
Hopefully now you’ve pinned down the culprit of the discolored pool, so let’s get down to business!
It may seem like the end of the world (or at least the summer) when your pool turns into a slimy green mess, but rest-assured, I’ve got you covered.
If you follow these six simple steps, I’ll have you back on your floatie in clean water in no time.
1. Can You Fix Your Pool's Chemistry?
If your pool is dark green, bordering on a blackish color, it may be more effective to drain the pool completely and acid wash the surface.
Rob at Dengarden says “if you can see at least six to eight inches below the surface of the water, most likely the pool can be treated chemically.”
If not, you will need to make your own decision about whether to drain the water or continue to try treatments.
2. Lower Your Pool's PH Level
You'll first want to test your pool to get a good idea of how much it needs to be lowered.
There are lots of testing kits available (check out the best pool test kits) that range in cost from under $5 to well over $50, but a good kit like this one from AquaChek (click here to check the price on Amazon) will serve your purposes just fine.
- 7-Way Strips Measure:Free Chlorine, Total Chlorine, Bromine, Total Hardness, Total Alkalinity, pH and Cyanuric Acid
- Just dip and wait 15 seconds
Since your pool is green, we already know the chlorine level is probably way too low, so you can skip testing that if you’d like.
The main thing you will be testing is the PH level.
A healthy PH level for a pool is right around 7.5 (source), but for this project, we want it even lower—below 7.2.
This will keep the water from becoming even more cloudy in the following steps.
Once you know what the PH level is, you can use a sodium bisulfate product to reduce it.
Simply follow the manufacturer’s instructions for adding the product to your pool and test it again in a few hours.
How much you add will depend on how acidic your pool is.
It’s always recommended to use about ¾ as much as it calls for to begin with so you don’t overdo it.
3. Shock Your Pool!
No, this doesn’t have anything to do with electricity (that would be scary!)
Shocking the pool is a method of adding a super shock liquid chlorine like Aqua Chem (click here to check the price on Amazon) to the water to instantly kill off most of the bacteria and algae.
- Kills bacteria and algae
- Creates sparkling water
Most pool shock products give great instructions on how much to use for various situations, but Pool Spa News states that scientifically, to de-structure the DNA of algae, you need to chlorinate the water to 30 ppm (or 30 parts per million).
Use your testing kit to reach the right balance.
4. Pump and Filter
Next, you’ll need to pump the water and filter it to regain balance. How you do this will depend on the type of filter you have.
If you have a DE or a sand filter, you’ll want to backwash the filter before you do anything else in order to remove dirt and sediment.
Pool Center gives great directions here on how to do this, but the basic steps are:
Shut off pump, roll out backwash hose, check waste line for any closed valves.
Turn the multiport valve handle to backwash, or slide a push pull valve.
Turn on the pump. The water should flow out backwash pipe or hose.
Backwash until water runs clear, about 2-3 minutes.
Shut off pump, turn valve back to filter, turn filter back on.
Note lower pressure on filter tank, and increased flow rate.
5. Floc Your Pool
After this process, your pool will still probably be a little cloudy from leftover residue—specifically, a “high concentration of microscopic particles of dirt, bacteria or other substances that are resistant to pool chemicals and small enough to pass through filtration.” (source)
Adding a flocculent helps the debris clump together so that it can easily be vacuumed from the bottom of the pool, leaving you with crystal clear water.
6. Kill the Algae
You’ve probably eliminated most of the algae in your pool by now and you may even feel that another step is just not necessary, but taking this one extra step could possibly keep you from having to repeat this entire process again in another week.
The thing is that algae grows very quickly and can take over your pool from just a few tiny spores.
A good algaecide like this one from Kem-Tek (click here to check the price on Amazon) can kill off those remaining microscopic spores, and continued treatment can prevent it from returning.
Additional Tips for Maintaining Your Pool Going Forward
The easiest way to clean your pool is to maintain it well enough that algae and debris don’t get out of hand.
Here are a few simple things you can do to make sure your pool water stays crystal clear:
“An ounce of prevention is worth a pound of cure,” so they say, and that couldn’t be truer than it is with swimming pool maintenance.
A little extra TLC on your pool every week will keep you from having to muck out a dirty green mess once a month.
Now, go grab your suit and dive in!