If your pool water has gone cloudy or the filter pressure keeps climbing, the sand inside is usually the problem. Getting the amount right matters. Too little and the water channels straight past the media. Too much and you choke the flow.
How Much Sand for a Pool Filter: The Short Answer
A standard 20 inch filter on a 50,000 litre pool takes roughly 40 to 50 kg of #20 silica sand.
That figure moves with your tank, not your pool. A bigger tank needs more sand. The pool volume only tells you whether the tank was sized correctly in the first place.
Fill the tank about two thirds full. The empty space above the sand bed is called freeboard. Your filter needs it to backwash properly.
How Many Bags of Sand for a Pool Filter in South Africa
Here is where most online guides fall down. They quote pounds and gallons for American tanks.
South African filters are sold by bag rating instead. You will see them listed as 3 bag, 4 bag, 5 bag and 6 bag. The number tells you how many bags of media the tank holds when filled correctly.
So if you have a 5 bag filter, you need five bags. The work is in confirming your rating and buying the right grade.
Check the data plate on the side of the tank. It carries the model and the media capacity. If the plate has faded off, send us a photo of the filter and we will identify it for you.
Why Bag Ratings Beat Pool Size When Working Out Pool Filter Sand
Two homes in Durbanville can have the same 40,000 litre pool and different filters. One runs a 3 bag tank, the other a 5 bag. Same water, different sand order.
Always buy to the tank rating. Never to the pool.
How to Work Out Pool Filter Sand by Filter Size
Work from the tank, in this order.
- Read the bag rating off the data plate on the side of the filter.
- Buy that number of bags in #20 silica sand.
- Fill to roughly two thirds of the tank and leave the freeboard clear.
If the data plate has faded or the filter was fitted before you moved in, send us a photo. We will identify the tank and tell you how many bags it takes.
What Sand to Put in a Pool Filter
Use #20 silica sand. The grain size is graded to trap debris while still letting water through at the right rate.
Do not use builders sand or beach sand. The grains are the wrong size and shape. They pack down, block flow and push sand back into the pool.
Alternatives to Silica Sand for Pool Filters
- Zeolite. Traps finer particles than silica. Costs more per bag.
- Glass media. Lasts longer than sand and backwashes with less water.
Both need different quantities to silica. Check the manufacturer rating for your tank before you switch.
When to Change the Sand in Your Pool Filter
Replace the sand every three to five years. Heavy use and a lot of leaf debris will shorten that.
Backwash when the pressure gauge sits 8 to 10 psi above its normal running pressure. Regular backwashing extends the life of the media.
Signs Your Pool Filter Sand Needs Replacing
- Water stays cloudy after a full backwash.
- Pressure climbs again within days of backwashing.
- Return flow is weak with a healthy pump.
- You find grit on the pool floor near the returns.
How to Add Sand to Your Pool Filter
- Switch the pump off at the isolator. Do not rely on the timer.
- Remove the multiport valve to open the tank.
- Scoop out the old sand. Protect the laterals at the bottom.
- Half fill the tank with water first. It cushions the laterals as the sand goes in.
- Add the new sand slowly to the correct level.
- Refit the valve and backwash for two to three minutes to clear the dust.
Cracked laterals are the most common mistake on a sand change. They send sand straight back into the pool and mean opening the tank twice.
Pool Filter Sand Replacement in Cape Town
Our team changes filter sand across Cape Town and the Western Cape. We bring the correct grade, handle the old media and test the pressure before we leave.
We also pick up the faults that a sand change alone will not fix. Worn laterals, a tired multiport valve or a pump that is undersized for the tank.
Send us your filter details for a quote.
Pool Filter Sand Questions We Get Asked
How often should I replace the sand in my pool filter?
Every three to five years for most pools. Sooner if the pool takes heavy debris or runs year round.
What happens if I put too much sand in a pool filter?
You lose the freeboard the tank needs to backwash. Flow drops, pressure rises and the filter stops cleaning properly.
Can I use normal sand in a pool filter?
No. Use #20 silica sand. Builders and beach sand are the wrong grade and will pack down or blow back into the pool.
How do I know when to backwash my pool filter?
Backwash when the gauge reads 8 to 10 psi above its normal pressure. Note the normal reading after a fresh sand change so you have a baseline.
Why is my pool still cloudy after adding sand to the filter?
Give it a full day of filtration first. If it stays cloudy, check your chlorine and pH, then look at the laterals and the multiport valve.
