Pool Filter Quickly Clogging Up (within days or hours)

If your pool filter gets clogged in a few hours or days after cleaning the filter, it’s an indication that it could be more than just a dirty pool.

So what causes the pool filter to clog quickly and what should you do to fix the problem? The answers to these questions and more will be revealed in this post. Let’s dive in.

pool pump and equipment
pool filter and equipment

Reasons Why Filter Clogs Quickly

Here are common reasons why the pool filter gets clogged quickly:

1) Algae in The Pool

If the pool is affected by algae, the pool filters can get clogged very quickly. Algae are tiny aquatic plants (or organisms) that grow in pools and in large groups. These plants can clog up the filter easily during pool water circulation.

In fact, we have an entire article dedicated to this: What to Do if Swimming Pool Filter Not Filtering Algae

There are different types of algae that can affect pools but the most common is green algae.

To know if you have algae in the pool, check for green, blue-green, or black patches in the water and around the pool walls. This signifies the presence of algae.

You can also check the pool pH, chlorine levels, stabilizer, and total alkalinity. If these are out, algae may grow.

Something to note is you may think you don’t have algae, or you got rid of it. This is a common mistake amongst pool owners. They think they’ve killed all the algae, but in actual fact, it’s still there.

So how do you fix this problem?

What To Do If Filters Clog Quickly With Algae

The best thing to do is to kill the algae. You can do this by shocking or super chlorinating the pool to kick the chlorine levels up to between 10 and 20 ppm. At this level, the algae don’t stand a chance.

The algae will die, turn white, and drop to the bottom of the pool.

Before you shock the pool, you should ensure that the chlorine stabilizer level is below 50 ppm. You should also ensure that the pH and water chemistry are balanced.

Keep in mind that you may actually need to maintain this chlorine level for several days to get rid of the algae entirely.

When the algae is dead, you’ll need to continually filter your water. When the filter blocks up, set the pool filter system to backwash or waste setting so the dead algae can be flushed out of the system. You can do this on sand and DE filters but cartridge filters usually don’t have a waste setting.

So to remove the dead algae in a cartridge filter system, you should use a pool vacuum or a flocculent. Find out how to use a flocculent here.

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HTH 67029 Drop Out Flocculant Swimming Pool Cleaner, 1 qt

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If you have a lot of algae, you’re going to find this process frustrating because it could mean cleaning the filter multiple times a day. But stick with the filtering and cleaning of the filter and you will eventually get there.

You may also try using a skimmer sock. They can be effective in preventing filters clogging up. More details here: What is a Pool Skimmer Sock, and Do You Need One?

2) Excessive Debris

Another reason for pool filters clogging quickly is excessive debris. Your pool filter system is designed to trap debris like leaves and grass clippings in the pool water. If there is too much debris, the pool filter will get clogged quickly.

To know if this is the problem, look in the pool water. If the water seems cloudy or unclear, it’s because there are debris and contaminants in the water.

Let’s find out how to fix the problem.

What To Do If Filters Clog Quickly With Excessive Debris

The best thing to do is to first remove the debris in the pool water. You can do this using a pool scoop net and a pool vacuum. Then you’ll need to clean and rinse the pool filters thoroughly to get rid of stuck debris.

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If you have a cartridge filter system, you can take out the filters and soak them in filter cleaner to remove oils and grease in the pleats. You can also use a soft brush to stroke the pleats to remove stuck grime.

Black Diamond Stoneworks Ultimate Spa Filter Cleaner Fast-Acting Spray for Hot Tub, Jacuzzi & Pool Filters.

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The next thing I recommend is vacuuming to waste. If you don’t have a waste setting, you can purchase a portable pool vac that will do the job.

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Vacuuming to waste will mean that all of that dirt and debris will bypass the filter and exit the pool. When you do this, you’ll need to top up the pool water and adjust the pool chemical levels.

3) Sand Grade Incorrect

This problem is rare and it only happens in sand filter systems but if you just changed the sand grade in the filter tank, this could be why the pool filter clogs up quickly.

Perhaps you weren’t sure what sand to put in your filter, or you accidentally used the wrong sand grade. If this happens, the filter will get clogged quickly, especially if the sand grade is too fine. If the grade is too fine, it means that there isn’t much space between the sand grains, which can cause them to get clogged easily by debris and fine dirt.

Check your instruction manual or check the sand grade specifications, which are sometimes on the filter tank.

What To Do If You Have Used the Incorrect Sand Grade

The only thing to do in this case is to change the sand to the right grade. You’ll have to empty the sand filter and put in new sand. That said, the right grade of sand for most pools is 20-grade silica filter sand.

4) Too Much DE (Diatomaceous earth)

If you’ve recently topped up the DE in your filter, and it’s clogging quickly, it could be because you added too much DE. DE filters need the right amount of DE and the correct DE grade to filter effectively.

After backwashing your DE filter or installing a new one, you’ll need to add DE. Most filters will need 3-6 lbs (1-3 kg). Check your user guide for the exact amount.

If you suspect you added too much DE, you can backwash the filter to remove it and top it up with the appropriate amount.

5) Sand Level Is Too High or Low

When you have too much or too little sand in the pool filter, the filter will not work properly or efficiently. The wrong level of sand means that debris can be forced into the sand instead of being trapped at the top of the sand canister. This will clog the sand system quickly.

To know if the sand is too low or high, you’ll need to open the filter tank. Usually, sand filters have marks on the inside of the tank that tell you where the sand should reach. If yours doesn’t, check the instruction manual.

If you have found you have too much sand, this is how to fix it…

What To Do If You Have the Incorrect Sand Level

If the sand level is too high, you need to take out some sand. Just scoop it out. If the sand level is too low, you guessed it, add some more. Be sure to use the same grade of sand already inside the canister if you are topping up the sand.

6) Filters Too Small

Every pool filter system should be matched to the size of the pool. If the filter is too small, it will get clogged quickly. You should know that many of the Intex, Summer Ways, and Bestway filters do clog quickly, due to their sizes.

In general, the best practice is to buy the largest filter you can afford. If you are looking at upgrading your filter, make sure the pump will supply the filter with enough water too.

8) A Faulty Spider Gasket Or Multiport Valve

This is common with sand filter systems. The multiport valve and spider gasket control the direction of water and debris in the pool.

Swimming Pool Multiport Valve
Swimming Pool Multiport Valve

If the multiport valve or spider gasket is faulty, your filter may not backwash or clean effectively.

What To Do

The first thing to do is to open and inspect the multiport valve. We have a full article on this here: How to Replace a Spider Gasket in Multiport Valve

9) A Damaged Skimmer Basket

The water in your pool flows through the skimmer basket before going to the filter system. The purpose is to allow the skimmer basket to collect large debris in the water whilst allowing the smaller debris to go into the filter.

If large debris isn’t caught in the skimmer basket, it can get into the filter, clogging it up quickly.

To check this, turn off the pump and pull out the skimmer basket.

If the basket is cracked or broken, you’ll need to replace it. You can get a replacement skimmer basket here.

Tips To Prevent Pool Filters From Getting Clogged Quickly

  • Clean the pool filters regularly
  • Run the filters for at least 8 hours daily for proper cleaning
  • Scoop floating debris out of the pool using a scoop net
  • Vacuum the pool regularly or use an automatic pool cleaner
  • Backwash or clean filter regularly (2 or more times per month)
  • For cartridge filters, deep clean them twice a year.
  • Use the right grade and amount of DE and pool sand
  • Use a pool cover to cut down on debris entering the pool

Final Thoughts

In many cases, there may not be anything wrong with your pool filter. It may be clogging quickly because it’s doing its job. That is, removing algae or other debris.

If this is the case, as long as you’re treating the algae, you’ll just need to persevere and keep cleaning the filter when it blocks up. After a few days, your pool will clear, and you won’t need to clean your filter so often.

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