Sand in Your Pool? Here’s Why—And How to Fix It

Starting to see little islands of sand gather on your pool floor? Unfortunately, that doesn’t mean you’re getting a personal pool retreat and beach vacation in one (if only). What it actually means is that you probably shouldn’t even swim in your pool! That is, until the problem that’s causing the sand is sorted out. Until then, chances are that your waters aren’t safe for swimmers.

Thankfully, keeping sand out and getting your pool back into working order can be easy as a trip to the beach. Well… almost. I’ll explain the two equally dangerous reasons why there’s sand coming into your pool (hint: in one case, it’s not sand at all!) and explain how to get that sand out—and be sure it isn’t coming back. Time is of the essence for this one, so let’s get started.

The Secret Lies In Your Sand Filter

If you’re getting little islands of sand in your pool, the first and most common place to look is at your pool filter type. You have a sand filter, don’t you? Yeah, I thought so.

The reason why you’re finding sand in your pool is that the sand filter media of your pool filter is somehow coming back through your pool’s return lines. And that’s a problem. It means that some section of your pool filter is broken and leaking sand out. This is not going to be a situation where you just let your powerful robotic vacuum take care of it on its own.

(If you don’t have a sand filter, uh oh. Skip down two sections.)

Sand In Your Pool from Your Filter? Act Fast

Sand might be small, but its presence in your pool indicates a larger problem. In order to understand why a sandbar in your pool is a serious matter, let’s revisit just how a pool filter works.

A pool filter is a unit that connects through plumbing to your pool’s circulation system, and it works in partnership with as well as protects your sanitizer. While the sanitizing chemicals you add to your pool might kill contaminants, your pool filter is what actually removes them. In the case of your sand filter, it uses sand media to catch these nasty contaminants and push out clean water. A faulty pool filter means that the contaminants in your water continue to exist in your pool, which greatly reduces the effectiveness of your sanitizer.

Seeing sand in your pool also indicates that all those contaminants your sand is supposed to keep out of your pool are coming right back in. That means you can’t count on your sanitizer to be keeping your pool safe from bacteria—including the type that can potentially make you sick—until the problem is fixed.

What you see is as a pile of sand? That’s like an island vacation for bad bacteria! Let’s get your filter back to working order, and keep them suntanning elsewhere.

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How to Fix Your Sand Pool Filter

Certain parts in your sand filter might have been broken due to recently moving your filter, such as when you open and close your pool. But sometimes, parts can just break when they reach a certain age and level of wear.

In order to fix your sand filter, you’re going to need to replace at least one part, usually either what is called the standpipe or one (or more) of the laterals.

The standpipe is the long pipe that runs down the center of your pool filter. It’s made of rigid, thick plastic—but unfortunately, that doesn’t mean it’s indestructible. You can’t miss it. It spans the entirety of your pool filter, from the multi-port valve at the top down to the laterals.

The laterals are the most common part to break. There are usually eight to ten laterals in sand filters, and they keep sand from entering your pool along with all that newly-cleaned water. Laterals do this by having tiny perforations that only allow water through. Of course, if one or more of your laterals is cracked, sand is going to sneak right in.

All you have to do is replace the cracked part—that process is common sense—in a series of steps that also involve changing the sand in your filter. Here’s the play-by-play: 

1. First, power off your pump. Drain your filter by removing the drain plug at the bottom of the filter.

2. Next, remove the multiport valve by gently turning it and twisting up. Pulling too roughly here can crack the laterals, so no Olympic moves!

3. Open the tank and cover the standpipe with duct tape so that sand doesn’t find its way in.

4. Use a Shop Vac to suck up the old sand. Then, rinse out the laterals the tank with a garden hose.

5. Next, replace the parts!

6. Using the garden hose, fill the tank halfway with water. Hold the standpipe and laterals centered and in place while you do this. This water will cushion the laterals from the incoming sand.

7. Add the new sand media. This time, it’s staying in your filter.

8. Fill the tank to the top with water. Replace the multiport valve and make sure all connections are secure.

9. Prime your pump and power it on. Backwash the filter for at least two minutes, or until you see the filter’s sight class is clear.

10. Run the filter—no more tiny islands in your pool!

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How to Get Sand Out of Your Pool—In Three Steps

Now that you’ve solved the problem—a broken sand filter—it’s time to solve the symptom of the problem. I like to do this after fixing the filter to avoid constantly repeating this process. Thankfully, it couldn’t be easier to do, especially if you have a robotic vacuum. 

1. Here Comes the Brush

To start off, you’ll want to brush all the sand into a localized area, or a few. If you want to do this in the easiest way possible, I suggest using this patented 360-degree bristles brush. Its shape keeps sand in your pool from dodging its powerful bristles.

2. Vacuum It Away

Power on your beast of a robotic vacuum and let it do the job. Don’t have one? Turn your multiport valve to “filter” and manually vacuum the sand back into the filter. Womp womp.

3. Back to Balance

Remember how I said having sand in your pool is like giving contaminants an island getaway? It’s time to test your water, rebalance your chemicals, and make sure they’re not so happy after all.

Wait… You Don’t Have a Sand Filter?

If you don’t have a sand filter, give that, ahem, “sand” a little push with your brush. If it quickly disperses into a cloud, it’s not sand after all—it’s mustard algae! You’re going to need to take some steps to get that algae out of your pool (and when the job is done, disinfect that pool brush).

Yeah, That’s Mustard Algae. Here’s Why That’s a Problem

Mustard algae doesn’t look like its green cousin. It’s not particularly slimy or clingy, which is why it often gets mistaken by pool owners everywhere for sand, dust, or a pesky metal stain. It’s also chlorine resistant, and as tenacious as a cockroach.

Like these horrific insects, it can survive outside of conditions you would think possible—namely, outside of the pool. Mustard algae can cling to bathing suits, pool equipment, anything that might come back into the pool or be exposed to water sometime soon.

If you have mustard algae, you can be certain that your chemical balance is out of whack. It exhausts your sanitizer in a jiffy, which then throws all your other chemicals off. That’s why at the end of this next process, we’ll use a perfect chemical balance as evidence that you’ve sent mustard algae packing. Let’s go.

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How to Get Mustard Algae Out of Your Pool—In Seven Steps

Ready to get that mustard algae (not sand!) out of here? Just follow these steps and you and your water are in the clear.

1. First, take care of the stuff outside of the pool that mustard algae might be clinging to. Machine wash your swimsuits, disinfect and clean pool toys, and put any pool brushes, hoses, or other equipment in the shallow end of your pool—that way when we shock your water, we’re also sanitizing these tools.

2. Next, it’s time to brush—and I mean really brush. Mustard algae spores might be clinging to your walls completely invisible to the naked eye, so you’re going to want to brush the entirety of your pool walls and floors. In order to save yourself a chunk of time—and back and hip pain—I highly suggest you use the patented 360-degree bristles brush. It was developed by longtime pool servicers to be the easiest to use ever. When that’s done, manually vacuum your pool. A robotic cleaner might reintroduce mustard algae in, so it can be tabled (and disinfected!) for now.

3. Next, test and balance your pool water. Then, give your pool another thorough brushing.

4. Triple-shock your pool. That means three pounds of pool shock for every 10,000 gallons of water your pool contains (and if you’ve never calculated your pool size before, now is the time).

5. In the days following your shock treatment, keep brushing the pool and rebalancing your chemicals.

6. After a few days, shock your pool again—but this time, make it the normal dose. That’s one pound of pool shock for ever 10,000 gallons of water your pool contains.

7. Last but not least, check your chemical balance. If it’s stable and on the mark, you’ve excited your mustard algae infestation. Great work.

Leave the Sand at the Beach!

You stopped some nasty contaminants from using your water as a luxurious getaway, so now it’s time for you to relax. Thanks to you, there’s one convenient and newly-safe place to do just that: your pool. And if sand ever makes its way back in, you’ll know just what to do. Enjoy.


This article explains how you can backwash your pool filter efficiently. Want to know how to clean the bottom of your pool? Read more here.