Troubleshooting Pool Filters – Sand, DE and Cartridge

Sand collecting at the bottom of your pool? Extremely high pressure gauge readings? Cloudy pool water? Sounds like your pool filter is in need of some troubleshooting! Lucky for you, we have collected a few of the most common pool filter problems, and have quick and easy suggestions to help turn things around. Nothing more frustrating than an expensive service visit just to learn a pool valve is in the wrong position!

Let’s dive right in to some of our most common problems we often see and hear about with Sand, DE and Cartridge Pool Filters.

Stop Sign

Before you go any further, let’s take a close look at that filter pressure gauge. So many pool filter headaches can be avoided by ensuring you have a pressure gauge that is functioning properly. A broken pool pressure gauge will very quickly send you on a wild goose chase.

  • Tap the face or casing of the gauge firmly to ensure the needle isn’t sticking in place.
  • Keep a spare pressure gauge handy to swap in and double check the readings are consistent.

After inspecting the pressure gauge, make sure to check that the filtration system is running for an appropriate amount of time. The right duration of run time will be unique to your pool, so refer to your pump and filter sizing, your pool size and bather usage.

Problem: Sand or DE is collecting in the pool

With both Sand Filters and DE Filters we often hear homeowner’s having difficulty with sand or DE powder finding its way into the pool, and typically collecting in the bottom of the pool.

  • General Solution: Check your push-pull valve or multiport valve to ensure it’s firmly in the correct position. It’s possible the handle was left in an in-between position and is allowing the leakage to occur.
  • Sand Filter Solution: Most common issues are that one of the lateral arms within the filter has a crack in it, and has created an opening for sand to slip through. This will require opening the filter up, scooping out some sand and inspecting the laterals one by one. Also, what kind of sand are you using? No. 20 Silica Sand is fairly common, but many homeowners end up using a sand particle that is smaller than recommended for their filter (refer to your owner’s manual).
  • DE Filter Solution: The first thing to check is a worn out or town septa, which may be allowing DE to flow into the pool. The septa nylon mesh can possibly be repaired, but in our opinion it will only be a matter of time before it gives out again. Also to check, DE may be flowing back to the main drain or skimmer when the pump is shut off. Make sure there is a Check Valve between the pump and filter to eliminate this possibility.

Problem: Reduced flow of water through the filter

Is your pump running at full capacity but there’s little to no water flow coming from your return lines? Read on.

  • General Solution: If your filter is doing the job it’s intended to, it should be collecting dirt and other debris within the filter tank, and therefore slowly over time building up to a higher level of pressure. Each filter and manufacturer is going to have a different standard, so be sure to refer to your owner’s manual.
    • As a general rule of thumb, if your pool filter is brand new it hypothetically will have a beginning PSI of 10, over time as the filter does it’s job it may creep up to read 20. At this point in time, when the PSI has increased around 10, it will be time to clean your cartridges or backwash. Over time you will find that after each cleansing the PSI doesn’t drop quite to the low level it began at, your new “fresh” PSI reading might now have creeped up to be 20 or more. At a certain point you will need to recharge your filter by replacing the filter cartridges, replacing your sand, or replacing your DE grids.

Problem: Low flow rates in the system

If you are finding that the flow rate is reading low, but your pressure gauge is reading high, there’s something restricting water flow in the system.

  • General Solution: A clogged filter, closed valve, closed jets, or a clog with another piece of your pool equipment can be causing this issue. Rule out each part of your filtration system piece by piece to isolate where the restriction is.
  • General Solution: A drop in the return flow may be traced back to a clogged skimmer basket, or pool pump basket. Clean the baskets and rule them out as a problem.
  • General Solution: If both the filter pressure reading and the flow rate are low, then it’s probable that your pool pump is undersized or has problems of it’s own.

Problem: Poor dirt and debris filtration

Too much dirt in your water? Too cloudy?

  • Cartridge Filter Solution: Poor filtration without the pressure reading increasing may point to worn out or even torn filter cartridges. There may just be a tear in the filter fabric that is allowing debris to pass straight through. Closely inspect each cartridge and repair or replace as needed. It’s not a bad idea to keep two sets of cartridges on hand, ensuring no down time while you wait on a replacement.
  • Sand Filter Solution: If the sand media has been charged incorrectly, channels in the sand may have formed and water is passing through unfiltered. You may need to recharge the filter. Also, if the sand filter hasn’t been backwashed thoroughly, mud balls may be forming within the filter. Or in some cases the sand may have calcified and won’t perform as expected. With proper care and maintenance your sand media typically shouldn’t need to be replaced for at least 4-5 years, if not longer.
  • DE Filter Solution: Coagulation or solidification of the DE often is the leading culprit with DE filters. If the DE is hardening, remove and clean the grids and recharge with fresh DE powder. Be careful not to feed the DE powder too quickly into the skimmer as feeding the DE too quickly can cause an uneven application of the DE, and thus poor filtration. If your DE filter is over-sized, or your pool pump is underrated, you may find yourself with inadequate pressure to be able to properly (evenly) coat the septa.

There you have it, some of the most common pool filter problems, with quick and easy at home checks that can be performed. We always recommend checking the owner’s manual for your specific pool filter as you may find install and care instructions that are unique for your specific brand and size pool filter.

Feel free to stop by and say hi in the comments below or give one of our pool professionals a ring at 800-772-0467. Thanks!

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Brian Champ
When Brian isn't writing pool-related articles, he enjoys anything that will take him outdoors: hiking, biking and trail running name a few. Brian is excited to share his pool knowledge with helpful how-to guides, product reviews, comparisons, and more!