Why is My Pool Filter Blowing out Sand?

Are you scooping out sand from the bottom of your pool? It means the sand filter of your pool is broken, and it needs immediate attention.

There can be many reasons that will make you ask why is my pool filter blowing out sand. But only a few need immediate fixing. As a pool enthusiast, I have rounded up everything you need to know to fix those issues here.

Let’s take a look at the basics of a pool filter and dive deep to fix it if broken.

How Does a Pool Filter work?

The pool filter is like a sand bucket with a water intake at the top and an outlet at the bottom. Water with dirt and debris gets into the top, and gravity makes it flow through the bottom outlet.

Why is My Pool Filter Blowing out Sand

In the meantime, dirt in the water gets attached to the sand surfaces, and only the clean water comes out to the pool. In this way, a bucket full of sand does all the cleaning.

Sand in the pool filter is larger than any play sand grains. Besides, the grains are more pointy than smoothened play sands. Those sharp edges hold the dirt and separate them from water.

A set of six to eight concentric pipes form the lateral. Filtered water flows out through these pipes to the pool. The top and bottom of the filter are sealed with rubber washers. These soft rings ensure no fluid gets in or goes out from the filter.

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Why is My Pool Filter Blowing out Sand?

It is effortless to check whether your pool filter is blowing out sand or not. If you see any or both of these signs, get ready for some filter fixing.

  • A sand layer at the bottom
  • Smoky water than usual

Both pool maintenance professionals and homeowners focus on two major reasons for a sand-blowing pool filter.

Shattered Lateral

See how helpful it was to know about the pool filter basics? Now, you know about the lateral and their functions. Those concentric pipes at the filter bottom carry the clean water from the sand bucket.

If there is any crack on any pipe or joint of the lateral, both dirty water and sand will get direct access to the pool water. This free access will turn the pool water too cloudy with a layer of sand on the bottom.

You will find a perforated vertical pipe, aka standpipe, in the sand. It carries the filtered water to the lateral. If the joint between the standpipe and lateral is cracked, the result will be the same—freeway for the sand and dirt directly into the pool.

Snapped Seal

Sand filters keep the dirty and filtered water separated. Obviously, it will have many rubber seals or washers to seal the joints between the standpipe, inlets, and outlets.

Unlike any seal in water supply pipes, rubber seals in the sand filter face harsh chemicals, dirt, and many more. You can imagine how vulnerable they are to snapping. These chemicals either corrode or harden the washers. Eventually, they break down quickly.

A broken seal cannot keep the sand and dirty water separated. So you will find all the sands on the pool bottom and dirt in the water.

How to Fix the Sand Blowing Filter?

You can fix any broken filter that is blowing sand in three easy steps. Of course, these steps come with multiple functions, but they are not complex at all. We have rounded them up in the easiest way so that any pool owner or maintenance professional can do them.

Replace Broken Parts

Step 1: Turn the water circulation off in the filter. Unplug the bottom of the filter and wait till all the water is dripped off.

Step 2: It’s time to unscrew the top of the filter. Unscrew the collar holding of the multiport assembly. Besides, unscrew all the unions of the holding pipes.

Step 3: This is a tricky step. You need to pull off the multiport assembly to expose the sand inside the filter. Use duct tape to cover the endings of the standpipe before emptying the sand. If you want to make the job tidy, use a vacuum.

Step 4: Bend all the outlet pipes of the lateral to a vertical position. Now pull out the manifold to check any crack on the lateral and fix it. Professional maintenance companies recommend replacing the part if the damage is too big. Repairing with adhesives will make you repeat the whole process very soon.

Refill Sand in the Filter

As the manifold is out so the sand in the filter will be exposed to you. It will be easy to refill or replace the sand with a new one. Make sure you read the instruction manual to find which sand to put in it.

Step 1: Put the manifold back into the filter body and fill it with water. It will clean any dirt in the standpipe or manifold.

Step 2: Hold the standpipe in the center. Ask someone to hold the pipe so that you can pour sand evenly around it. Remove the duct tape after the filter is all filled with sand.

Step 3: Now check all the washers in each connection or pipe joint. If you found any dripping or leakage, get a new ring or washer for it.


Backwashing a filter is the process when you pump water in the reverse direction. So the water will flow from bottom to top, washing all the clogged dirt in the sand. It is an effective way to clean a filter leaking dirty water.

When to Backwash a Sand Filter

It depends on the filter settings and water quality. Sometimes the water carries too much dirt and clogs the filter with dirt. So you need to do frequent backwashing.

Another way to find out is by checking the filter reading. When the reading shows 8 to 10-lbs above the clean, it’s time for a backsplash.

How do I know if my sand filter is bad?

Sand filters are the easiest way to filter your pool water without wasting too much effort. You just plug the power in and wallah. But what happens when the sand filter is greasy and doesn’t work correctly? For a lousy sand filter, the first thing you will notice is the sound. Then again, the water circulating time decreases, or sand flows backward. 

Here are the things you will notice if your sand filter is terrible,

  • Sand flows to the pool.
  • Water doesn’t clean properly.
  • Cloudy pool.
  • The filter is greasy.
  • Takes more time to filter the pool.

How often should you change sand in a pool filter?

Sand filters should be replaced every time you feel something is wrong with the filter system. But on average, you should replace the sand within 3-4 years. The time may vary, depending on the brand and condition of the filter. Out-of-the-box sand filters tend to degrade faster. It is not the sand, but the quality of the filter that is bad.

How often should I backwash my sand filter?

Backwashing a sand filter can improve water circulation and distort any impurities inside. When the summer hits, try cleaning the pool three times per month. The more you use the pool filter, the more you need to backwash. Frankly speaking, it is all up to you.

How often should a pool filter be changed?

The pool filter hardly needs any replacement. If your pool filter doesn’t clean the pool properly, try replacing the sand filter. Out-of-the-box pool filters degrade faster, whereas specialized filters last longer. A pool filter from a reputed brand lasts more than 15 years before you need any changes.


I am sure you won’t be worried anymore about why is my pool filter blowing out sand. Next time if you feel edges on your feet in the pool or can’t see through the water even with your swimming goggles, you know what is wrong.

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