Why Is Dirt Getting Back Into My Pool?

Have you ever finished vacuuming your pool only to realize that all the dirt magically found its way back into your pool? Or, did the dirt shoot through your return jets after going through your filter?

We all know that cleaning and maintaining your pool isn’t always easy. That is why when you realize all of your hard work has been for naught, you tend to get a little frustrated.

There are a few reasons why sand, dirt, and debris might end up in your pool after vacuuming and filtering.

Have You Backwashed Your Filter?

If you have a sand or D.E. filter, you understand that backwashing is a normal part of your pool maintenance routine. If you have a cartridge filter, you are accustomed to cleaning your cartridges yourself. Sometimes, though, after backwashing your filter, you can experience a little dirt back into your pool. Have you ever wondered why?

Sand Filters

If you open a sand filter, you will see a network of tubes called laterals that extend from a central hub. Water passes through the laterals, which also blocks the sand from entering the water. If you find dirt or sand escaping the filter after backwashing, you may have a broken or cracked lateral.

To determine if one of your laterals is compromised, you will have to open the tank and examine the tubes yourself.

In some instances, we have also seen that there could also be an issue within the valve itself. We recommend taking the cover off your valve and inspecting the internal gaskets and O-rings. One of your O-rings may be torn or out of place.

Cartridge Filters

Cartridge filters do not have backwashing capabilities. Filter cartridges must be cleaned by hand or acid-washed. Filter cartridges are made from spun-bound polyester designed to increase surface area for better filtering. If one of your cartridges is ripped, debris can make its way back into the pool.

Whenever you clean your filter, it’s good practice to examine the cartridges for damage and tears.

Diatomaceous Earth (D.E.) Filters

D.E filters, to me, are similar to both sand and cartridge filters. They are similar to sand filters because you will have to backwash them in order to clean them. However, they are like cartridge filters because they use internal grids to filter out debris and dirt.

In some cases, the filter grid may crack or rip, allowing dirt and D.E. powder to pass through the filtering stage and land back in your pool. In this situation, you will have to open your filter and disassemble your grid cluster to examine each grid.

If all of your grids are in perfect shape, remember to check your valve. Open the cover of your valve and make sure the gaskets and O-rings are set properly and are in good condition.

How Old Is Your Sand?

When was the last time you replaced the sand in your filter? As sand begins to deteriorate and break down, the particles become smaller in size. This size reduction allows sand to pass through the filter and back into your pool.

In addition to sand in your pool, you may notice your water is more cloudy than normal. This is also another indication that you need to replace your sand.

Is Your Pump Too Large For Your Filter?

Pool owners often ask if it’s possible to oversize a pool pump and the answer is, yes, you can. By definition, a pump is too large for your filter when the pump pushes more gallons per minute (GPM) than the filter allows.

When this happens, the pump is pushing water through the filter faster than the filter can catch the debris. As a result, the debris ends up back in the pool.

Is Your Pool Covered?

High winds and run-off contaminants can add to the dirt that ends up in your pool. If you vacuum your pool in the morning and notice more dirt in your pool later in the day, you might want to consider purchasing a pool cover.

The pool cover will not only protect your pool from dirt, leaves, and other run-offs, but it also reduces your consumption of chlorine as well. In our opinion, it’s also a great investment when you’re ready to close your pool for the winter.

Do You Have A Leak In Your Return Line?

In an in-ground pool, you may have a series of three-way fittings that allow you to plumb in several returns. In an above-ground pool, there may be a header that feeds into the return line.

If dirt or sand is coming through the return line, there may be a leak in the return plumbing. In this case, we recommend using Fix-a-Leak or a similar product that finds and seals the leak.

I’ve Checked Everything Above

If you’ve checked all of the items above and you’re still experiencing a good amount of dirt and debris back into your pool, leave a comment below or you can ask our pool community in our Facebook Group or our INYO Forum.

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19 thoughts on “Why Is Dirt Getting Back Into My Pool?

  1. We purchased an above ground Bestway pool kit from Costco. Everything works great, and we set it up exactly as the manual described; we filled the sand filter, gave it an initial cleaning, and all seemed good. Only thing is that from the very start, every time I run the pump, a plume of dirt comes into the pool. The only solution I’ve found is to backwash and rise the filter every single time I run it. I know this shouldn’t be the case, I should only have to backwash and rinse once a week. It’s brand new, so the sand isn’t old. I’ve tried pool sand and zeolite, both with the same issue. The sand is at the exact height it should be. The water tests have come back good from Leslie’s, so it’s not like the water is the issue. I’m stumped.

  2. I have a two-speed pump attached to my filter.
    Daily, I change to high speed.
    When I do this, extremely dirty (green) water comes thru the return port for about 5 seconds.
    Then, all seems OK. I have never noticed this before.
    My pool is still not in the ‘clear’ phase and is being treated for algae.

    1. I tried running our two speed pump on low once. Won’t be doing that again. It simply didn’t move enough water to keep the algae away. Went back to full speed and haven’t had issues since. They never give you more pump (more expensive) than what you absolutely need.

  3. Have a Hayward cartridge filter and after I run the filter, they’re what looks to be sand at the bottom of my inground liner pool in the corner where one of the return lines is. Along with that, there is ‘sand’ building up at the bottom in areas where the wall and floor meet. When I brush the ‘sand’ (at least that’s what I think it is) it vanishes into a cloud. Im really not sure what it is considering the filter cartridges were just cleaned, and the filter isn’t a sand filter. I also put banish in my pool tonight just to see if it maybe mustard algae, which in that case banish would kill it.

      1. We are having something similar happening to ours. It’s also a Hayward, and the water is clear n everything fine, we checked the laterals and new sand added. The debris like described like the person above that lines through the cracks of the liner, dark brown n dirt sand like appearance and when we use our dolphin to clean it there’s barely anything inside except a lil dirt the rest disintegrates. Once the pool is cleaned we turn back on the pump/filter and with a few minutes it’s back. We ruled out mustard algae as well. It keeps coming every time the filter is back on. Please help 🙏 at this point our pool won’t be running and it’s only a year old

        1. I’m guessing algae, since you state the dirt kind of disintegrates when you touch it – the agitation of the filter may make it settle into the seams again when it is turned on. What does it feel like if you touch the dirt in the pool (slimy or gritty)? Do an Overnight FC Loss Test (OCLT) to see if the chlorine level dips overnight, which would indicate algae.

        2. Ashely
          Did you ever figure out what the problem was? Ours does the exact thing and we have been dealing with it since the beginning of last summer. If I leave my pump off the bottom of the pool stays clear but soon as I turn the filter back on the spots come back. We have treated it as algae and spent so much money and time trying to get rid of it and now I am thinking it’s never been algae to begin with.

  4. Can soil from potted plants be getting sucked into the atmosphere then into pool? I get dirt from them on my patio and wonder if this is causing dirt in the pool within a day of vacuuming! I do backwash. Filter is a year old, DE filter.

  5. If your cartridge is blowing back, open filter and verify that the breathe tube, quarter inch white tube runs up center of cartridge and just higher than cartridge, is plugged in bottom center and has screen intact. Screen mounts on top of tube and is for bubble release. Sometimes little filter comes off in cleaning, and sometimes in shipping. Sometimes they aren’t even in filter to begin with. Most likely knocked off or forgotten in assembly at factory.

    1. Any idea where one can find these screens? I noticed both of my filters are missing the screens at the top and I am getting a lot of debris blown back into pool.

  6. New Pentair pool filter system cartridge .
    Pool is crystal clear nothing on bottom after vacuuming (battery vac not through filter)
    But after you Ron filter we have sediment on bottom?

        1. When I start my Pentair DE pump it shoots out green debris for the 1st 30 second then its clear. I have backwashed. I have checked the grids a couple time and haven’t found any tears? Any tips?

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