Pool Sand filter blowing out sands

Why Is My Pool Filter Blowing Out Sand? [3 Main Reasons]

Looking at the sand in your pool, you must wonder why my pool filter is blowing out sand? If there is a sand filter in your swimming pool, it is unnecessary to mention the filter should keep the sand in it. But suddenly, if it starts throwing out the sand into the pool, your sand filter needs some fixing.

There might be something broken like cracked laterals or a broken standpipe. Also, there might be a broken seal that needs to be fixed or replaced. Usually, you can fix this sand filter on your own, but it will take some time.

So, we have developed this guide for your assistance.

Why Is my Pool Filter Blowing Out Sand?

Sand filter system next to a pool in your own garden

There can be various reasons for it. In this section, we will highlight some of the most common reasons behind this issue. Once you identify the problem, you can fix it. But first, you need to understand how a sand filter operates.

Sand filter operation

This sand filter is a large tank that is filled with sand (pool-grade). This sand is much coarser than that regular play sand. So, water enters the tank from an inlet right at the top of the filter. Then, it gets pulled downward, and any purities are removed from it as well.

At the bottom of the tank, water enters those laterals with miniature perforations to keep sand out. Filtered water circulates straight back into the swimming pool from those perforations. If this sand filter is not performing its function, you will see sand in the pool. There can be two primary reasons for that.

  • Shattered laterals
  • Broken seal

Shattered laterals

Now you know why your pool has sand in it and how you can fix the issue. Those pipes right at the bottom of the tank have clean water from your pool's sand bucket.

If there is a crack on pipes or joints, sand and dirty water will reach your pool. And this will result in cloudy pool water that has a layer of sand at the bottom.

This perforated vertical pipe is also called a standpipe. It carries the filtered water to the filter's laterals. If the joint between those laterals and the pipe has any crack, you will see cloudy water and sand layer at the bottom of your pool. So, fix the joint between the lateral and the pipe.

This lateral and pipe joint can also shoot out the sand in your pool. So, appealing a lateral or the standpipe or fixing any cracks between them is crucial. This entire lateral and pipe system keeps the filtration system working correctly.

Broken seal

Those sand filters are designed to keep filtered water separate from dirty water. In addition, it will have several rubber seals, which are also called washers. These washers are there to seal the joints between the outlets, the inlets, and the standpipe.

These washers have to deal with harsh chemicals as well as dirt, and so much more. Therefore, these washers are pretty vulnerable, and they tend to snap or break.

The chemicals can corrode these washers, and they end up breaking down faster. In addition, these broken washers cannot keep filtered water separate from dirty water, and sand will blow out into your pool.

Should Sand Come Out When You Backwash?

You might be thinking that sand should come out when you backwash a sand filter. The backwash is a process when you pump water into your sand filter in a reverse direction. Hence, water should flow from down to up, and it will also wash away any clogged dirt or sand.

It is a very effective way to properly clean your pool filter that is leaking dirty water in your pool. Later on, you can set a schedule to backwash your sand filter depending upon your filter setting and water quality.

There are times when too much dirt in the water, which clogs the sand filter system. In such a scenario, you will have to do frequent backwash. You can also check the sand filter reading. And if it shows 8 lbs to 10 lbs above the clean level, it's time to run that backwash.

Can You Put Too Much Sand in A Pool Filter?

Can You Put Too Much Sand in A Pool Filter

When dealing with the issue of "why is my pool filter blowing out sand," you might think you should change the quantity of sand in your sand filter.

But, you can't put too much sand in your pool filter because it won't work correctly. You might even end up breaking it during the assembling process. But, on the other hand, if there is too little sand in it, you will have cloudy water.

No matter how much your sand filter runs, that blurriness in your pool water is going to stay there. Pool filters can hold sand in 50-pound increments. So your filter might come in different ranges like 100 pounds, 150 pounds, 200 pounds, and 250 pounds.

But it would help if you kept in mind that you cannot fill it with and right up to the top. It needs to be only around ⅔ complete. That is to allow a freeboard space within the tank right above the sand bed. There will be blowback if you fill it too much, especially if you have done a backwash.

Will Sand Ruin A Pool Filter?

Pool Architecture System

Most of the filters these days come with particular types of valves that can clean the debris. If you try to change the position of this valve, you have to shut the pump off. Otherwise, you will end up damaging the entire system just because of a valve.

It would help if you got rid of as much debris or algae out using a net as a vacuum. You can also vacuum the sand. It can easily last from three to five years in a sand filter before you have to change it.

If there is high pressure and it doesn't subside even if you have gone through multiple backwashes, then it's time to change your sand. The old sand at the bottom of the pool will also become fine. Replace this old sand to make sure your system works properly again.

Therefore, you have to keep it in good shape and perform backwash regularly. Changing it after three to five years is a must, or the entire filtration system of your pool will collapse.

 If you vacuum with the "value setting" on your filter, all the sand will stick within your vacuum cleaner. It could damage the filter as well. But with the "waste setting," the pool water and sand will not enter the filter. However, you will end up losing water from your pool.

How Full of Sand Should A Pool Filter Be?

As we have mentioned above, pool filters range in their capacities to carry sand. Smaller units might have a tank of 50 pounds in them for the sand, and they also come in 50-pound increments.

So, usually, you will find a 100-pound, 150-pound, 200-pound, or 250-pound pool filter. But no matter the tank capacity, you only need to fill it with about two-thirds of the total space. So leave some room there at the top.

If you fill it too much, the entire system will lose its force, and there is a chance of clogging. On the other hand, if you fill it too little, your system will blow out dust into the pool.

With this much filling, there will be enough space present on the top. Of course, the quantity may vary based on your needs and requirements. But this is the recommended amount of sand that should be in your pool filter.

How Do I Get Sand Out of My Pool Filter?

How Do I Get Sand Out of My Pool Filter

For this, you will have to disassemble your pool filter and look for any broken parts, as we have mentioned above. But before that, you will also have to replace sand. Replacing damaged parts might not need much elaboration, but replacing the sand does need some explanation.

The amount of sand that will go there in your filter depends upon the size of your pool filter. It is going to range between 100 pounds to 350 pounds. You can purchase some new sand from your pool supplier and ensure that it has the proper consistency.

With this, you need to order a complete kit of laterals. You can read the owner's manual of your pool and fit the filter to find out how many laterals and what types are needed. If you think the washer needs to be replaced, order that to replace it. Go for the right size of washer based on the older one that you have.

Step 1 - Drain your filter

Turn your pool's circulation system off. Now drain your filter using that screw present at the bottom of the filter. Before you proceed to the next step, wait for the theater to stop dripping from the bottom of the filter.

Step 2 - Unscrewing the assembly

Unscrew the collar holding and remove it from the multiport valve assembly of the filter. Also, unscrew those unions holding those pipes in place directly to the assembly. If your system doesn't have unions, you must cut those pipes and install new unions when reassembling your filter.

Step 3 - Vacuuming the filter

Pull that multi-port valve assembly off and then right away cover the standpipe end using duct tape. This process will keep the sand from entering the pool. Now you can empty that sand from your filter with the help of a wet or dry vacuum. It might take a while, particularly if you have a large-sized filter that has a capacity of 350 pounds.

Step 4 - Taking the manifold out

It's time to lift that standpipe and bend the laterals in a vertical position. Turning the laterals will allow you to pull the manifold outright from the filter's body. Now, clean the manifold and look for any cracked or broken laterals.

Replace all the cracked laterals. But if you are unsure whether those laterals are broken or not, it's always best to replace them. Also, check the standpipe for any cracks and replace them.

Step 5 - Lower the manifold back

Now gently lower your manifold right back into your pool's filter body and bend those laterals horizontally to lock them back. Next, it's time to center your standpipe and fill your filter approximately half with clean water. With water, you are preventing any damage to your laterals when you are pouring the sand.

Step 6 - Pouring sand in

You have to keep the standpipe centered as you pour new sand. You will need a helping pair of hands here. When you are done pouring your sand, you can remove the tape you attached early from the end of the standpipe.

Step 7 - Pushing the assembly into the standpipe

Now check the washer at the bottom of the multiport valve assembly and replace it if you see any signs of wear and tear.

You can push the multiport assembly right back into the standpipe and secure that collar by holding it to that filter body. Check those washers on each of your unions before you screw them back onto the assembly. And make sure to replace many of them that are worn out.

Step 8 - Backwash the filter

The next and final step is to set your filter to backwash and start your pump for a couple of minutes. Doing this will clear out any sand or debris.

 After that, you can set the control of your filter to rinse. Now start the pump for another couple of minutes. Then, you can do it again if you think the water is not clear. In the end, you can set the control to its normal positions "filter, and your entire job is complete.


Broken parts are the main reason behind "why is my pool filter blowing out sand." Therefore, you have to check and make sure that you replace any of these parts.

Also, check the amount of sand in your filter and replace that too if needed. Go for the replacement parts after consulting the owner's manual for the pool filter. Finally, make sure to backwash your filter regularly to prevent it from clogging.