You backwash, you add a filter cleaner, and the pressure still climbs back up in a week. Your water never quite clears.
Sand does not last forever. The grains start sharp and catch dirt. Years of water tumbling them wears the edges round, and round sand catches almost nothing.
Signs the sand is finished
Look for more than one of these before you commit to the job.
- The filter has run five to seven years on the same sand.
- Pressure climbs back within days of a backwash.
- Water stays hazy no matter what the chemistry says.
- Backwash water never runs fully clear.
- You pull out clumps instead of loose grains.
Sand that is clumped but not old may only need a chemical soak. Try that first. Our guide on cleaning a pool filter covers it.
Buy the right sand and the right amount
Use pool filter sand. It is graded to a specific grain size, usually number 20 silica. Play sand from the hardware store is too fine and will blow straight through into your pool.
The amount is printed on the filter label or in the manual. Weigh it out instead of guessing, because too much sand blocks the top of the tank and too little lets water channel past.
Some filters also call for a layer of pea gravel underneath. If yours does, it says so on the label.
Empty it out
Turn the pump off at the breaker. Close the valves on both sides of the filter, or drop the water below the filter inlet.
Pull the drain plug at the bottom of the tank and let it drain. This takes a while.
Take the multiport valve off the top. Loosen the collar, then lift it straight up and set it aside where nothing will land on it.
Now tape or cap the standpipe, the pipe running down the middle. If sand gets down that pipe it goes straight into the laterals and then into your pool.
Scoop the old sand out with a plastic cup or a wet vacuum. Go slow near the bottom. The laterals down there are brittle plastic fingers, and a shovel cracks them.
Check the laterals while it is open
This is the part people skip and regret.
With the tank empty, look at every lateral. Any crack, split, or missing slot sends sand into the pool forever, and you will not know until the new sand is already in.
Replace a cracked lateral now while you can reach it.
Fill it
Rinse the tank out. Fill it about a third of the way with water first, which cushions the laterals from the falling sand.
Keep the standpipe covered and centered. Pour the sand in slowly and even it out by hand as you go.
Uncover the standpipe, clean the o-ring and lubricate it with silicone, then set the valve back on and tighten the collar.
Rinse before you filter
Do not go straight to FILTER. New sand carries fine dust that will cloud your pool.
Set the valve to BACKWASH, run the pump two minutes, then RINSE for one minute. Repeat until the sight glass runs clear. Then set it to FILTER.
Write the new pressure number down. That is your clean baseline for the next several years. Our guide on backwashing a pool filter is built around that number.
When to call
Stop if the valve will not come off the tank, if the laterals are cracked and you cannot source parts, or if sand is already blowing into the pool.
A tank that is cracked or rusted through is not worth new sand. Our page on repair versus replace covers where that line sits.
We stock filter sand and parts at the supply store, and our Texas RAIL licensed crew will do the whole change for you. Call (361) 575-5821.
Frequently Asked Questions
How often should pool filter sand be changed?
Every five to seven years for most home pools. Heavy use, hard water, and frequent algae blooms shorten that.
What kind of sand goes in a pool filter?
Pool filter sand, usually number 20 silica. Play sand and builders sand are too fine and will pass through the laterals into your pool.
How much sand does my pool filter need?
The amount is printed on the filter label or listed in the manual. Do not estimate. Too much blocks the top of the tank and too little lets water channel past the sand.
Why is sand blowing into my pool?
Almost always a cracked or broken lateral at the bottom of the tank, or a standpipe that was left uncovered during the fill. A damaged standpipe o-ring can do it too.
Do I need to backwash after changing the sand?
Yes. New sand carries fine dust. Backwash two minutes, rinse one minute, and repeat until the sight glass runs clear before you switch to filter.
Can I use glass media instead of sand?
Many sand filters accept recycled glass media, and it filters finer and lasts longer. Check that your filter manufacturer approves it, and use the amount they list for glass rather than the sand weight.
