When to change the filter sand and how to do it

Signs that the sand is worn out

The age of the sand is only a guide. The real test is how the filter performs. Consider a change when:

• the water turns dull even though pH and chlorine are correct and the pump runs enough hours,
• the pressure on the gauge rises very quickly after every backwash, or stays high even right after one,
• you need to backwash more and more often although the way the pool is used hasn't changed,
• when you open the filter you find clumps, a hard crust on the surface, or "channels" in the sand where water passes through without being filtered.

Before changing the sand, rule out the simple causes: a proper backwash and balanced chemistry. Very often cloudy water is down to the pH or hardness, not the filter.

If you see sand on the floor near the return inlets, the problem may be a broken lateral inside the filter. You will see it anyway when you empty the filter.

What you need

The quantity and grain size are given on the filter label or in the manufacturer's instructions. It is usually silica sand made specifically for pool filters and, in many models, a bottom layer of coarser gravel that protects the laterals. Never use building sand or beach sand: the grain size is wrong, and it contains dust and salts.

You will also need a new O-ring for the lid or the valve, a small container for scooping out the old sand (or a wet vacuum), a small bag to cover the central pipe, and gloves.

The change step by step

1. Switch off the pump, turn off its circuit breaker, and close the valves before and after the filter.
2. Drain the water through the drain plug at the base of the filter.
3. Undo the connections and remove the multiport valve or the lid.
4. Cover the opening of the central pipe so no sand falls into it.
5. Remove the old sand carefully. The laterals at the bottom are plastic and break easily, so don't dig hard near them.
6. Rinse the inside and check the laterals; any that are cracked are replaced.
7. Fill the filter about halfway with water so the sand falls gently. Add the gravel first, if your model calls for it, then the sand up to the height the manufacturer specifies, keeping the central pipe upright and centred.
8. Clean the rim thoroughly, fit the new O-ring and put the valve back on.
9. Open the valves, backwash for a few minutes to flush out the dust from the new sand, then rinse, and finally switch to filter.

Sand and glass media raise dust when poured from the bag. Pour them slowly into a filter half full of water, and avoid breathing in the dust.

Sand or glass media?

A change is a good opportunity to think about the material. Glass media goes into the same filter and works with the same valve.

Which material suits your filter depends on its model; more on filter types in pool filters. Whichever you choose, note the date of the change in your maintenance schedule, so you know when the next one will be due.

Questions

See also