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

Nearly 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, quality water. The sand filter is a device that effectively filters and retains impurities. Nevertheless, it must sometimes be changed. When ? Why ? How ? Our answers in this file.

Why should a swimming pool sand filter be changed?

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

  • The aging of the sand: with the passage of water and impurities, the sand wears out, becomes thinner, rounder and can no longer ensure its filtering power properly. It lets impurities pass.
  • Limestone : the limestone, naturally present in the water, attaches itself to the sand. Over time, the latter clogs and forms clumps, which does not allow the impurities to be filtered properly.
  • Clogging: by dint of retaining impurities, they clog the filter and the rinsing function is no longer sufficient to eliminate them. Some blocks of impurities accumulate and form piles of micro-residues.

Thus, when the sand filter is no longer able to perform its filtering role, 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 micro-organisms, algae and bacteria which can cause allergic reactions and require a complete replacement of bathing water.

When to change the sand filter of your swimming pool?

Depending on the hardness of your water and the exposure of the pool (the less it is protected against impurities and plant waste, the dirtier it gets), the sand filter should be changed every 2 years, every 3 years, every 5 years or every 7 years. Nevertheless, these durations are possible on the condition of regularly maintaining your sand filter.

If you are unsure if it is time to change your sand filter, a simple little test can be performed:

  • Check the flow rate at the nozzles after cleaning. If it’s lower than usual, it’s probably time to change the filter.
  • If your water remains cloudy despite good maintenance, the filter is no longer sufficient.
  • By plunging your hand into the sand tank, you find that it forms compact clumps. It’s time to replace it.

How to change the sand filter of 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 pool, already washed and sanitized, and not traditional sand. For your filtration to be very fine, it is recommended to buy fine sand whose grain size varies between 0.4 and 1.2 mm. However, fine sand clogs up faster. Consequently, it is wise to associate it with a sub-layer of coarser sand or gravel, the grain size of which varies from 2 to 5 mm.

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

  • The sand filter with valve on top : these are the most common, 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 change your sand filter.

Step 1: drain the water from the sand filter

Begin by draining all the water present in the sand filter. Without this essential first step, you will not be able to remove the sand with a view to replacing it.

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. Just let the water come out on its own. Don’t hesitate to plan something to scoop or wipe off the water that escapes if you are working 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, because 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 directly on the side to empty the sand on the ground. Pay attention to the bottom of the tank, because that is where the strainers are. Be careful not to damage them.

Empty the sand completely and rinse the filter thoroughly with water.

Step 3: pour new filter sand

Once the sand has been removed, it’s 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, put the sand filter back in its original location and put the drain plug back in place.

Once the filter is in place, pour a third of water into it to avoid damaging your strainers with falling gravel and to limit flying dust. Protect the fragile elements, such as the deflector cap or the pipes, then pour the sand for the swimming pool after having equipped yourself with a mask so as not to breathe in the silica dust.

Ideally, place 1/3 coarse grit on the bottom and 2/3 finer grit on top. Be careful, however, because the sand filter must not be completely filled. Leave about 1/3 of its height free to allow water to circulate freely and facilitate the backwashing 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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