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Sand filter systems are the way to go for efficient, low-cost, low-maintenance pool maintenance. The sand filters rarely clog, so most of the time you’ll have crystal clear water in your pool without having to worry about work day in and day out or being too hard on your wallet. Every few years, however, you’re due for a sand change.

But how do you change the sand in your sand filter system? Before we get into the specific steps, you first need to decide on a type of sand. After that, you can jump right in with the step-by-step instructions.

What is filter sand?

The filtration system fishes all sorts of unwanted foreign matter out of the pool water. Insects, algae cells, bacteria, and anything else that is responsible for pool water turbidity or can cause illness is removed by the sand filtration system.

The sand filtration system is based on sand as a filter medium. Polluted pool water flows into the filter system. A large part of the impurities then remains attached to the filter sand and the almost completely clean water comes out of the sand filter again.

Sand is an effective filtration medium and is used in wastewater treatment, septic system and also in purification of drinking water.

Types of filter sand

Not all sand is the same.

We can’t say it clearly enough: use only filter sand made for pool filters.

To the layman, sand always looks the same, but cheap play sand for the sandbox is absolutely not at all suitable for the sand filter system. If you use the wrong sand, it can cause sand buildup in the pool or even damage your filter system.

As a rule, you will find in the instruction manual of the sand filter system or on the official website of the manufacturer a note, on the grain size of the filter sand to be used. The manufacturer specifies whether sand of grain size 0.4 to 0.8 mm or 0.7 to 1.2 mm may be used. The exact grain size distinguishes filter sand from filter gravel.

The idea behind this is that smaller sand grains clump together more tightly and therefore create a higher pressure inside the filter. Otherwise, the filter stars might not be designed for a fine grain size, so the filter sand from the sand filter system ends up in the pool. If in doubt, opt for filter sand with a grain size of 0.7 mm to 1.2 mm, as this will not cause any damage.

Quartz sand

Quartz sand (also called silicon dioxide or SiO2 in technical circles) is the most common filter sand. Quartz sand is made from ground quartz, which has sharp, jagged edges that excellently filter foreign particles from the water flow.

Quartz sand is available in various degrees of purity. The range extends from 80 percent to sand with 95 percent SiO2.

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Zeolite Sand

The alternative for quartz sand is made from volcanic rocks called zeolites. Zeolite sand has a surface area 100 times larger than other types of filter sand due to its sponge-like shape.

The great advantage in using zeolite sand is that it effectively removes chloramines from the water, which are a waste product of disinfecting the pool with chlorine products. The zeolite sand traps the chloramines in the individual sand particles for this purpose.

If you have a lot of problems with foreign matter in the pool, use a corresponding amount of chlorine, and need to shock chlorinate often, zeolite sand is a great way to control chloramines and reduce the need for chemicals.

Glassand

Glass sand is the environmentally friendly alternative for silica sand. This type of sand is made from 100% recycled glass. The material is smooth to the touch, yet can filter foreign particles as small as 3 microns in diameter (that’s 0.000003 meters).

The glass sand grains have different sizes, which minimizes channeling. Channeling means that pool water makes its way through the sand and passes through the filter almost unfiltered.

We also recommend glass sand for hard pool water problems. This is because the negatively charged glass grains are excellent at absorbing manganese and iron particles.

Why do you need to change the pool filter sand?

The dirty water that flows through the sand filter system is cleaned by the filter sand. Dirt, bacteria, algae and other foreign particles are trapped in the sand grains in the process.

It is not visible to the eye, but in fact all three types of sand have a rough surface to which contaminants from the water flow attach. Over time, however, the rough, spiky surface of filter sand wears away. The increasing smoothness causes the filtration efficiency to decrease.

The result is sand in the sand filter system that can barely filter the water. You will notice this condition in the pool if the water is cloudy, you often shock chlorinate, and you frequently have to backwash the sand filter system. So the filter sand has a life cycle, but how long does it last?

How often to change the sand filter system sand?

As more and more contaminants accumulate over time, the life of the filter sand is limited to approximately 5 years. In the first years, the filtration efficiency even increases, because the impurities associated with the sand grains increase the surface area of the sand grains, and thus the water flowing through the filter is filtered better.

The efficiency of the filter decreases when the filter sand becomes too smooth and can no longer absorb foreign particles. You can tell by two indicators that the sand has passed its peak:

The filter performance decreases because the pool water has made a channel through the filter sand and is hardly filtered anymore. Visible impurities and turbidity appear more frequently in the pool. The time between two backwashes becomes shorter and shorter.

The pressure of the filter pump increases because it is more difficult for the water to get through the clumping sand.

Does the sand really need to be changed or is there an alternative?

When do you need to change the sand and when do you just need to clean it?

With your sand filter, you need to keep a close eye on the pressure gauge. To do this, make a note of the pressure displayed after a backwash. When the filter pressure reaches a value that exceeds the initial value by at least 10 psi (~ 1 bar), it’s time for the next backwash. Cloudy pool water – when the pool chemistry is balanced – is another reason to backwash.

Backwashing is an important part of pool maintenance because it washes the sand, in a sense. Some dirt is flushed into the waste. However, some water is lost during backwashing, which you will need to replenish afterwards.

Backwashing helps with increasing pump pressure and increases filter performance for some time. However, the sand is the real filter media. This becomes increasingly slippery over time and gradually loses its filtration performance. In a time window of about 3 to 5 years, the sand must be replaced, otherwise too high filter pressure and impurities in the water will become a constant companion.

There is a trick you can use to increase the filtration performance of your filter sand. Add a dose of filter cleaner (amount according to manufacturer’s instructions) to your sand filter system annually. The main purpose of the agent is to wash out grease, oil and other contaminants that are not completely removed during backwashing.

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Step-by-step instructions: Replacing the sand

Now it’s time to change the sand. The instructions have a lot of steps, but most of them are done quickly.

Tool list

  • Screwdriver
  • Garden hose
  • Flashlight (or a phone)
  • Duct tape or rubber stopper
  • Pool filter sand
  • Small shovel or a wet vacuum (“Shop Vac”)
  • Pocket knife
  • Sewage hose
  • Mask

In case the pipe needs to be cut:

  • Saw
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Step 1: Turn off the pump

You can only replace the sand when the pump is turned off. Turn off the filter pump and also check that the timer is not set so that the pump turns right back on.

Step 2: Drain the filter

Remove the drain plugs or plug from the bottom of the filter tank and drain all the water from the filter.

Draining may take some time. Open the drain several hours before starting the actual work.

Step 3: Remove the valve

Now remove the pipes and tubes from the valve. Some old sand filter systems have PVC pipes that are permanently attached to the valve. In this case, you will need to cut through the pipe with a saw.

After the pipe is sawed through, you can install a screw cap so that you can disconnect more easily the next times.

Use the screwdriver to remove the screws that attach the valve to the tank. Slowly turn the valve and pull it upwards.

It is important that you turn the multiway valve carefully and also pull it up carefully, as the standpipe has more branches that end in the sand. The combination of the weight of the sand and your turns could otherwise damage the side pipes.

Step 4: Cover the opening of the standpipe.

In the center of the sand filter is an open pipe. The standpipe is intended for the pool water. Therefore, cover it with a rubber plug or some waterproof tape so that sand cannot get in. If some sand gets into the pipe, it will end up in the pool. This is one of the most common causes of sand in the pool.

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Step 5: Remove the sand

Removing the sand from the sand filter is a really tedious job that really gets on your back – unless you have a suitable wet vacuum.

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By hand with a small shovel, it would take forever. So either make friends with your neighbor who owns a wet vacuum, or get one yourself. This will save you a lot of the time and effort. In addition, such a wet vacuum is versatile and will still be very useful to you when vacuuming in outdoor areas.

When removing the old filter sand, be careful not to damage the water distributor, filter cross, filter star and vent hose. Then clean the filter housing with water.

Step 6: Rinse the filter

You have now removed most of the sand with the vacuum. Now, using the garden hose, flush the remaining sand out of the drain.

Now it’s time to check the sand filter system for any needed repairs. Using a flashlight or the flashlight on your phone, carefully inspect the pipes for damage. Cracked or broken pipes will cause sand to steadily enter your pool. If you see any repairs needed, now is the time to make them.

Step 7: Fill the tank halfway with water.

Screw down the drain of the tank. Now fill water into the tank with the garden hose. Hold the standpipe in the middle while doing this. The tank should be filled halfway.

The main purpose of the water is to protect the side pipes from the falling sand. When you fill the sand later, it will not fall on the pipes and damage them, but will just slowly and gently sink down in the water.

Step 8: Add the new filter sand.

First, put on the respirator to avoid inhaling dust during this step.
Also check the tape on the standpipe again.

Now hold the bag of filter sand with one corner over the opening of the tank and then cut that corner with the pocket knife.

A helper can be useful for this step because the sand bags weigh up to 25 kilograms and you will need to hold the bag with one arm for a short time.

The required number of bags of the filter sand depends on your filter tank. It is best to read what the manufacturer recommends in the instruction manual and on the official website.

Fill the new filter sand only to just below the boiler pitch. Be careful when filling so that the parts inside the filter system are not damaged. However, it must not be too little sand, because this would have a negative effect on the cleaning performance.

Again, remember to only use filter sand that is designed for your pool filter. Anything else could ruin your filter system. Sand that is too fine-grained could slip through the filter system’s mesh and settle in the pool as a fine layer of sand.

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Step 9: Fill the tank completely with water.

All the sand is in the tank. Now fill the filter tank completely with water as well.

Step 10: Reattach the pipes, valve and hoses.

Reattach the reusable valve, all pipes and hoses to the filter’s tank. Make sure all screws and connections are secure.

Step 11: Backwash and clear rinse

Connect the backwash hose and set the valve to backwash. Turn on the pump and run it for at least two minutes.

This will help you flush out the sand dust that settled on the inside walls of the tank during filling and the contaminants from the new filter sand.

Turn the pump off again. Now set the valve to rinse and let the filter run for another minute to allow the sand stirred up by the backwash to settle again.

Step 12: And (almost) done

Turn the pump off again. Set the valve to Filter and turn the pump back on. Check the pressure gauge. The gauge should read normal operating pressure. Make a note of this to know when the next backwash is due.

If after a few weeks the gauge reads 10 psi (1 bar) more than it does at the present time, you should backwash.

A final word

Some pool owners ponder the right filter sand for a long time. Sure, each type has its own strengths, but you can’t really make a wrong choice here.

Much more important than deciding which filter sand to choose is that you buy filter sand in the first place, and not resort to sand for the sandbox or from the beach. Your pool filtration system owner’s manual will provide you with all the important specifications needed to choose the right filter sand.

We hope that our instructions have helped you and that you have successfully replaced the sand. Now you really deserve a bath in clean pool water.

We wish you a lot of fun while bathing!

Larry has been a true water rat since childhood. Pure pleasure turned into a passion. That's why he is the first point of contact for friends and acquaintances when it comes to pool-related problems. He is an integral part of the PoolHandbook editorial team.