Domakihub How to Change Pool Filter Sand the Right Way
Step-by-step guide to replacing worn-out filter sand so your pool stays clear all season.
Reviewed by Domakihub pool pros · 2026-06-23 · 5 min read
Sand filters are the most common pool filtration choice across Greece, whether you run a private villa, a holiday rental, or a hotel pool — and the sand inside does not last forever. The video above by Swim University walks you through the full swap visually; this guide pairs it with clear written steps and practical tips suited to the Greek climate and pool season. Do this once every three to five years and your water will stay cleaner with far less backwashing and chemical correction.
Why filter sand stops working
Over time, pool filter sand becomes coated with oils, minerals, and fine debris that your backwash cycle cannot fully remove. The grains also round off — they lose the sharp edges that physically trap particles, so dirty water passes straight through. The result is cloudy water that stubbornly resists clarifiers and requires constant backwashing just to keep flow pressure acceptable.
In Greece, where pools often run eight or more months a year under intense UV and high bather loads, this degradation typically occurs in three to four years rather than five. High-calcium water from limestone-heavy aquifers accelerates the calcification of sand grains even further, so local pools usually need a change sooner than the manufacturer's guidelines suggest.
What you need before you start
Gather your materials in advance: replacement pool filter sand rated #20 silica (50 kg bags; confirm the exact weight your filter model requires), a wet/dry shop vacuum, a large bucket, a plastic scoop or garden trowel, Teflon plumber's tape, multi-port valve O-ring grease, and a garden hose. Avoid using metal tools inside the filter tank — they can crack the lateral assembly at the bottom.
Schedule the job for a calm morning when the pool equipment has been off for at least 30 minutes. In summer in Greece this is best done early before heat makes the work uncomfortable. Have a second person available if your filter tank is larger than 600 mm in diameter — the empty tank is manageable alone, but the filled bags are heavy.
How to change pool filter sand: 5 steps
- 1
Shut down the pump and relieve pressure
Turn off the circulation pump at the breaker, not just the timer. Rotate the multi-port valve to the Backwash position and hold the manual air-relief valve open until all pressure escapes and water stops flowing. Disconnect the drain plug at the bottom of the tank and let the tank drain completely — this can take 10 to 20 minutes.
- 2
Remove the multi-port valve and expose the sand
Unscrew or unbolt the multi-port valve from the top of the filter. Before lifting it off, wrap the standpipe opening with a damp cloth or tape to prevent sand from falling into it and damaging the laterals below. Set the valve aside on a clean surface. Use your shop vacuum to remove as much old sand as possible from the top; then scoop out the rest with your plastic trowel into a bucket for disposal.
- 3
Inspect and clean the laterals and tank
Once the tank is empty, lower yourself or a torch inside to inspect the spider-leg lateral assembly at the bottom. Flex each lateral gently — any that are cracked or broken must be replaced now, before new sand goes in. Rinse the inside of the tank with a hose, then check the standpipe for cracks. Replace the drain plug O-ring if it shows any cracking or flattening.
- 4
Add the correct amount of new sand
Fill the tank halfway with clean water first — this cushions the laterals from the impact of heavy sand. Pour in the new #20 silica sand slowly and evenly around the standpipe, keeping the cloth or tape over the pipe opening throughout. Fill to the fill line marked inside the tank, or to roughly two-thirds full if no mark exists. Do not overfill; leaving air space above the sand is essential for the backwash cycle to work properly.
- 5
Reassemble, backwash, and rinse before returning to filter mode
Remove the standpipe cover, apply fresh O-ring grease to the valve gasket, and reseat the multi-port valve. Reconnect all plumbing lines. Set the valve to Backwash and run the pump for a full two minutes — water will run cloudy and grey as fine dust flushes out. Switch to Rinse and run for 30 seconds to compact the bed, then move to Filter mode. Check pressure at the gauge: the starting pressure with fresh sand is your new baseline. Write it on a label stuck to the filter housing.
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FAQ
- How do I know my filter sand needs replacing rather than just a backwash?
- If you are backwashing more than twice a week to keep pressure within 7–10 psi of your baseline, or if the pool stays cloudy within 24 hours of adding a clarifier, the sand has likely lost its filtration ability. Another clear sign is visible cloudiness or debris returning to the pool through the return jets after a normal backwash cycle.
- Can I use play sand or beach sand instead of pool filter sand?
- No. Pool filter sand is a specific grade of silica with angular grains sized around 0.45–0.55 mm (#20 grade). Play sand and beach sand have rounded, inconsistently-sized grains that pass particles through or clog too quickly, and they may introduce contaminants. Always use sand sold specifically for pool sand filters.
- Is there a better alternative to traditional filter sand?
- Yes. Filter glass (recycled crushed glass) and ZeoSand (zeolite mineral) are two upgrades that many pool operators in Greece have switched to. Filter glass traps finer particles than sand, requires fewer backwashes, and lasts up to ten years. ZeoSand captures ammonia compounds as well as particles, which is particularly useful in pools with high bather loads such as hotel or rental pools. Both can be used in the same tank — simply adjust the fill quantity per the alternative media's instructions.