Easy Way to Clean Algae from a Pool Filter Cartridge

If you have a heavy algae outbreak in your pool, your pool filter has probably turned green. You may have found that it’s not easy to clean algae from a pool filter. Or the filter is blocked up.

So, is there an easy way to clean your cartridge filter of algae?

Algae can be cleaned from a pool filter cartridge by using a garden hose to spray down the cartridge. A cartridge cleaning attachment or fireman’s hose nozzle can make the job faster and easier. To get a deeper clean, simply soak the filter in filter cleaning solution or diluted muriatic acid.

Before jumping into the step-by-step cleaning guide, let’s examine why your cartridge filter can go green from algae.

Cartridge filter filled with green algae.
Cartridge filter filled with green algae.

Reasons Pool Filter Cartridges Turn Green

Your pool filter cartridge is green primarily from a build-up of algae on the filter. You may have noticed it was green during routine maintenance or perhaps you have had a large algae outbreak.

Your filter going green and clogging up with algae means the filter is working, but leaving it dirty will cause the filter to stop working efficiently.

Cartridge filters are incredibly efficient at filtering microscopic dirt, debris, and algae. Along with trapping dirt, the cartridge filter prevents algae from re-entering the pool.

However, they can only do so much by themselves regardless of filter type. Algae can only grow and invade your pool (and its filter) if the chlorine level drops below minimum levels. Most pools need a chlorine level of 1-3 ppm to keep algae away.

So, if you notice green deposits on your filter but your pool is still crystal clear, you’ve caught the early stages of algae trying to overtake the pool. So, after cleaning the filter, it’s crucial to re-balance the water chemistry (particularly chlorine levels) to prevent algae blooms.

But if you’re in the midst of trying to clear up a green pool, you’ll need to keep cleaning your green filter until the algae are gone.

Green algae on pool liner bottom
Green algae on pool liner bottom.

Cleaning Algae from a Cartridge Filter

Cleaning algae from a cartridge filter is a simple process. Follow the steps below to get your green cartridge filter looking good.

1. Turn Off the Pump

The first thing to do is to turn off the pump. Turning off your pool from its power source would be best. This will prevent any preset timer from kicking the pump back into action.

2. Depressurize Filter System

For your safety, release excess air from the filter system by opening the pressure-relief valve (usually on the top of the filter).

3. Remove Cartridge From Tank

The cartridge is usually protected under a latched lid. Simply unclamp the latches to remove the filter cartridge. If you’re unsure how to remove yours, consult your owner’s manual for instructions.

Once the cartridge is out, inspect it for wear or damage and replace it where needed. If the filter is extremely dirty, replacing it may be easier and more cost-efficient. If you do decide on replacing your cartridge, have a look at our recommendations: Replacement Pool Filter Cartridges – The Most Common

4. Clean The Filter Cartridge

Cleaning algae from your cartridge can be a little tricky, especially if it’s live green algae. Algae will turn a gray color when it’s dead and is easier to remove.

You can just use a garden hose to spray it down, ensuring you’re reaching between each pleat. You can also use a fire hose type nozzle for your garden hose. Ensure that the pressure of the water isn’t too high; otherwise, it can accidentally damage the pleats.

If you want, you can opt for a cartridge cleaning nozzle to get water into each pleat more easily. This will help, especially if the cartridge is very dirty.

Aquatix Pro Premium Pool & Spa Filter Cartridge Cleaner, Removes Debris & Dirt from Pool Filters in Seconds, Heavy Duty & Durable Pool Cartridge Filter Cleaner, for a Clean Flow of Water Today! (1)

Tip: you may need to deep clean your filter if it doesn’t come clean. See below for instructions.

5. Replace Cartridge

If the cartridge doesn’t need a deep clean, then you can secure it back into place. Secure the filter lid back on to prevent leakages and poor filter performance.

6. Repressurize System

When the cartridge is back in place, turn on the filter system but leave the air-relief valve open. Doing this will give the system an extra chance to clear built-up pressure. Once you get a steady spray of water coming from the valve, close it.

While the filter is running, check the pressure gauge to ensure it shows your filter’s normal pressure reading. If the pressure is more than 10 psi higher than normal, it could indicate the cartridge isn’t set correctly.

Cartridge filter with green algae and a clean cartridge filter after deep cleaning and hosing off.
Cartridge filter with green algae and a clean cartridge filter after deep cleaning and hosing off.

Deep Cleaning a Green Filter

If your filter is very green or is contaminated with oils, dirt, or calcium build-up, you’ll want to clean the cartridge deeply. This involves soaking the cartridge in a cartridge filter cleaning solution overnight.

While the cartridge is out of its housing, simply soak it in the cleaning solution after rinsing it down. Doing this will help the cleaning solution better infiltrate each pleat’s inner crevices.

It’s ideal to let it soak in a 5 gal (23 l) bucket of water mixed with the solution for at least 24 hours. Most pool owners choose to do this soaking overnight. But, if you have a second cartridge filter to hand, this can temporarily take the soaking cartridge’s place.

If you want, you can use muriatic acid to give your filter a thorough clean. To find out how to clean your cartridge with muriatic acid, check out our step-by-step guide: How to Clean Pool Cartridge Filter (Using Muriatic Acid)

Tools for Cleaning Algae from Filter Cartridges

High-Pressure Fireman’s Spray Nozzle

Sometimes your garden hose may not be strong enough to remove algae from filter cartridges. You can try a fireman’s nozzle. But be careful not to use it too close as excessive pressure could damage your filter cartridge

Gilmour 855032-1001 High-Pressure PRO Fireman's Spray Nozzle with Large, Red/Black

Pool & Spa Filter Cartridge Cleaner Nozzle

Using a cartridge cleaning nozzle instead of the standard garden hose nozzle can make it faster and easier to clean the green from your filter.

Aquatix Pro Premium Pool & Spa Filter Cartridge Cleaner, Removes Debris & Dirt from Pool Filters in Seconds, Heavy Duty & Durable Pool Cartridge Filter Cleaner, for a Clean Flow of Water Today! (1)

Is Pressure Washing OK?

It’s not recommended to use a pressure washer or power washer to clean your pool filter cartridges. The pressure from the water is likely to damage the filter paper or tear the pleats.

Instead, opt for a garden hose.

How Often Should You Clean A Cartridge Filter?

There are three separate times when you should be cleaning your filter cartridge to keep it pristine. These times range from every 2-6 weeks to 6-12 months.

If however, your filter cartridge is green, you may need to clean it daily until you’ve killed off all the algae. If the algae are bad, you may even need to clean it multiple times a day until you’ve filtered out a lot of the algae.

Regular filter maintenance should be as follows…

Gently rinse the cartridge using fresh water from a hose or sink every 2-6 weeks. And make sure you’re spreading each pleat to rinse off trapped dirt.

Every 1-2 months spray the cartridge with a cleaning spray, letting it sit for 15 minutes before rinsing it off with fresh water.

Lastly, deep clean the cartridge every 6-12 months in a diluted cleaning solution, allowing it to soak for 24 hours, finishing it off with a rinse from fresh water.

Green algae on above ground pool.
Green algae on the above-ground pool.

How to Prevent Algae Blocking Cartridge Filter

There are several ways to prevent algae from building up on the cartridge filter. And they all primarily deal with pool/hot tub maintenance. The main takeaway is to prevent algae from ever having the chance to grow.

Maintain Water Chemistry

Keeping on top of your pool/hot tub’s water chemistry is a surefire way to prevent algae from growing.

After dealing with an algae bloom, test your water chemistry daily. And then extend it to twice weekly during the swimming season. Keep chemical levels as follows:

  • Chlorine: 1-5 ppm
  • pH level: 7.4-7.6
  • Stabilizer: 30-50 ppm
  • Alkalinity: 80-120 ppm

Test Phosphate Levels

Aside from the usual chemical levels to watch for, keep an eye on phosphate levels. Algae thrive on phosphates, so if you’re getting a high reading, use a commercial-grade phosphate remover.

Let the remover do its thing and then shock the pool to help clear it. If you need help on how to shock your pool, check out our guide: How To Shock A Swimming Pool For Beginners (In 6 Easy Steps)

Use Pool Cover

A simple way to help prevent algae build-up is to cover your pool or hot tub with a cover while not in use. Get into the habit of using one outside of swimming season and before extreme weather conditions hit during the season.

backyard pool with installed cover
Backyard pool with installed cover.

Regularly Clean Pool and Equipment

To prevent algae from settling into cracks and crevices, brush down pool walls and vacuum weekly. And routinely inspect the filter and pump to ensure they are working efficiently.

A woman vacuuming the swimming pool floor
A woman cleaning the swimming pool.

Add An Algaecide

Adding an algaecide as a preventative measure will kill algae. However, make sure to use the correct dosage for either prevention or treatment. Too high a dose can cause staining and foaming.

Clorox Pool&Spa 43128CLX 42128CLX Pool Algaecide

Final Thoughts

Discovering your filter cartridge is green can be a pain. But, it is usually a sign that algae are getting ready to wreak havoc on your pool or hot tub.

Luckily, removing algae from your filter is an easy process. It’s also as easy a process to prevent algae from ever having the chance to build up on your cartridge filter and infiltrating your pool or hot tub.

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