Changing the sand in a swimming pool sand filter: when, why and how?


Almost 80% of the quality of your bathing water is ensured by the action of your filter. This part is therefore essential for the proper functioning of your pool and to allow you to fully enjoy swimming in good conditions, with healthy and quality water. The sand filter is a device that filters and retains impurities efficiently. However, sometimes it needs to be changed. When? Why ? How? ‘Or’ What ? Our responses in this dossier.

Why do you have to change the sand filter in a swimming pool?

Over time and with swimming, the sand filter wears out, becomes clogged and loses its effectiveness. Indeed, it is sometimes necessary to replace this device. Here are the reasons.

  • Aging of sand: with the passage of water and impurities, the sand wears out, becomes thinner, becomes rounder and can no longer ensure its filtering power properly. It allows impurities to pass through.
  • Limestone : limestone, naturally present in water, binds to the sand. Over time, the latter clogs and forms packets, which does not allow the impurities to be properly filtered.
  • The clogging: by dint of retaining impurities, they clog the filter and the rinsing function is no longer sufficient to remove them. Some blocks of impurities collect and form piles of micro-residues.

Thus, when the sand filter is no longer able to perform its role of filter, it is time to change it to continue the cleaning action. Without this filter, the pool water is no longer of sufficient quality to allow healthy swimming. However, unfiltered water full of impurities leads to the formation of harmful microorganisms, algae and bacteria which can cause allergic reactions and require a complete replacement of the bathing water.

When to change the sand filter in your swimming pool?

Depending on the hardness of your water and the exposure of the swimming pool (the less it is protected against impurities and plant waste, the more it gets dirty), the sand filter must be changed every 2 years, every 3 years, every 5 years or every 7 years. However, these times are possible on condition that you regularly maintain your sand filter.

If you’re not sure if it’s time to change your sand filter, a simple little test can be done:

  • Check the discharge rate at the nozzles after cleaning. If it’s weaker than usual, it’s probably time to change the filter.
  • If your water remains cloudy despite proper maintenance, the filter is no longer sufficient.
  • By dipping your hand into the sandbox, you see that it forms compact clusters. It’s time to replace it.

How to change the sand filter in a swimming pool?

Before you start changing your sand filter, you still have to choose the right product. Indeed, it is important to buy special sand for swimming pools, already washed and sanitized, and not traditional sand. For your filtration to be very fine, it is recommended to buy fine sand with a grain size ranging between 0.4 and 1.2 mm. However, fine sand clogs up faster. Consequently, it is judicious to associate it with a sub-layer of sand or larger gravel, the particle size of which varies from 2 to 5 mm.

To replace your sand filter, you will need to take its type into account. Indeed, there are two types of sand filters for the same filtration effect:

  • The sand filter with valve on the top : these are the most widespread, because they are less bulky. However, they are a little less easy and practical to maintain.
  • The sand filter with valve on the side : this model is equipped with a transparent dome on the top to cover an opening, which makes it easier to maintain.

Here are the steps to follow to change your sand filter.

Step 1: Drain the water from the sand filter

Start by draining all the water in the sand filter. Without this essential first step, you will not be able to remove the sand for replacement.

To do this, interrupt the filtration device and close the water inlet and outlet valves to prevent flooding. Then place the 6-way valve in the “off” position or the 5-way valve between two positions.

Open your filter and unscrew the drain plug. You just have to let the water come out on its own. Do not hesitate to plan something to scoop or wipe up the escaped water if you work in a technical room.

Step 2: remove the sand from the filter

If you have a pool sand vacuum, use it. On the other hand, avoid using a non-dedicated vacuum cleaner, as you will damage it very quickly.

Without this equipment, put on gloves and remove the sand by hand or with the help of a small container. If you can, pour the filter straight to the side to dump the sand on the ground. Pay attention to the bottom of the tank, because this is where the strainers are located. Be careful not to damage them.

Completely empty the sand and rinse the filter thoroughly with water.

Step 3: pour in new filter sand

With the sand removed, now is a good time to check that your sand filter is in good condition. Strainers are particularly important and must be checked. You can also lubricate the O-rings at the same time. Once done, return the sand filter to its original location and replace the drain plug.

Once the filter is in place, pour in a third of water to avoid damaging your strainers with falling gravel and to limit flying dust. Protect the fragile elements, like the deflector cap or the pipes, then pour the sand for swimming pool after putting on a mask so as not to inhale the silica dust.

Ideally, place 1/3 coarse grains on the underside and 2/3 finer grains on top. Be careful, however, because you must not completely fill the sand filter. Leave about 1/3 of its free height to allow water to circulate freely and facilitate the backwash action. It is therefore necessary to distribute the two types of gravel over the remaining 2/3 of the filter.

Step 4: restart the sand filter

Restart your filtration device in the rinsing position, then start a filter washing cycle to prevent sand dust from settling at the bottom of the pool.

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