Learning how to winterize sand filters for above ground pools is the best way to save yourself a massive headache—and a lot of money—once the weather starts to turn. If you live somewhere where the temperature drops below freezing, you already know that water is a powerful force. When it turns to ice, it expands, and if that expansion happens inside your expensive pool equipment, things are going to crack.
I've seen plenty of pool owners try to skip these steps, thinking a heavy cover on the pool is enough. It's not. Taking an hour or so in the fall to properly shut down your filtration system ensures that when the sun finally comes back out in May, you aren't staring at a split tank or a ruined multi-port valve. Let's walk through how to get this done right.
Why You Can't Skip Winterizing
It's easy to get lazy when the swimming season ends. The water is cold, the leaves are falling, and you just want to throw the cover on and forget about it. But sand filters are particularly vulnerable because they hold a lot of water deep inside that heavy sand bed.
If you leave water inside the tank and it freezes, the pressure has nowhere to go but out against the walls of the filter. You might wake up in January to a loud crack, and by then, it's too late. You'll be shopping for a whole new filter system instead of just enjoying your morning coffee. Beyond the tank itself, the small plastic parts—like the pressure gauge and the sight glass—are even more fragile. A little bit of prep work now keeps those parts in one piece.
Clean the Filter One Last Time
Before you even think about draining the system, you need to make sure the sand inside is actually clean. You don't want all that dirt, oils, and organic junk sitting in there for six months, hardening into a "brick" of gunk.
Start by giving your filter a thorough backwash. Let it run until the water in the sight glass looks crystal clear. Once that's done, switch it over to the rinse setting for about 30 to 60 seconds to settle the sand back down. This ensures that when you open things up next year, the sand is ready to work, rather than being a clogged mess that needs an immediate deep clean.
Draining the Tank the Right Way
This is the most important part of the entire process. Once you've turned off the pump and disconnected the power (safety first, always!), look for the drain plug at the very bottom of the filter tank.
Fair warning: this takes a while. Because the water has to seep through all that heavy sand to reach the drain, it isn't going to gush out like a fire hose. It's more of a slow, steady trickle. I usually pull the plug and then go work on something else for an hour.
Pro tip: Take that drain plug and put it somewhere you won't lose it. I like to put all the small winterized parts into the pump basket so they're all in one spot come springtime. If you leave the plug out, it allows any remaining moisture or condensation to escape throughout the winter, which is exactly what you want.
Managing the Multi-Port Valve
The multi-port valve—that big handle assembly on top (or the side) of your filter—is the most sensitive part of the system. It contains a "spider gasket" and several spring-loaded parts that can be easily damaged by ice.
If your filter setup allows for it, the best move is to actually remove the entire multi-port valve. Usually, this just involves unscrewing some heavy-duty plastic unions or clamps. Once it's off, you can take it inside a garage or basement where it won't be exposed to extreme cold.
If you can't or don't want to remove it, you must at least set the handle to the "Winter" or "Winterize" position. If your valve doesn't have a specific label for that, just set the handle halfway between any two positions. This lifts the internal diverter off the gasket, giving water a path to expand without crushing the seals.
What to Do with the Rest of the Parts
While you're at the filter, don't forget the "little guys." There are several small components that are almost guaranteed to break if they stay out in the snow:
- The Pressure Gauge: Unscrew this carefully. They are notorious for freezing and failing. Take it inside.
- The Sight Glass: That little clear plastic bubble is very brittle. Pop it off and store it with the gauge.
- The Air Relief Valve: If your filter has one on top, open it up to help the tank drain faster and then store it safely.
I always recommend applying a thin layer of silicone-based lubricant to any O-rings you encounter while taking things apart. It keeps the rubber from drying out and cracking over the winter. Just stay away from petroleum jelly, as it can actually degrade the rubber over time.
Moving vs. Tarping the Tank
Now you have a choice to make. A sand filter for an above ground pool is incredibly heavy because of the sand. If you have a small filter, you might be able to disconnect the hoses and lug the whole thing into a shed. This is the gold standard for protection.
However, for most of us, that tank is staying right where it is. If you're leaving it outside, make sure it's covered. A heavy-duty tarp or a dedicated equipment cover works wonders. You want to keep rain and snow from getting into the openings you've left unplugged. Just make sure there's still a little bit of airflow so you don't end up with a mold situation inside the tank.
Dealing with the Hoses
Don't leave your hoses attached. Plastic and vinyl hoses get very stiff and brittle in the cold. If they're full of water and that water freezes, they'll split right down the middle.
Disconnect the hoses from the pool (assuming you've plugged the returns and skimmer) and from the filter. Drain them completely, roll them up, and store them somewhere out of the sun. This also gives you a chance to inspect them for any tiny pinhole leaks you might have missed during the summer.
The "To Change or Not to Change" Sand Question
People often ask if they should change their sand while winterizing. My advice? Only if it's been 3 to 5 years or if you had a massive algae bloom that you just couldn't beat.
If your sand is still in good shape, leave it alone. Changing sand is a messy, back-breaking job. If you do decide to change it, winter is a great time to scoop the old stuff out so the tank is empty and light, but I'd wait until spring to put the fresh sand in.
Common Mistakes to Watch Out For
I've made plenty of mistakes over the years, so you don't have to. Here are a few things people often forget when they're learning how to winterize sand filters for above ground pools:
- Forgetting the pump: The filter and the pump are a team. If you winterize the filter but leave water in the pump housing, the pump's plastic volute will crack. Drain the pump too!
- Leaving the drain plug in: Even if you think the tank is empty, condensation builds up. Leave that plug out so the tank can "breathe."
- Using the wrong lube: Again, use silicone. Petroleum products are the enemy of pool gaskets.
- Losing the parts: Seriously, use a Ziploc bag. Tape it to the inside of the pump basket. You'll thank me in six months.
Final Thoughts on Winter Prep
It feels like a lot of work when you're doing it, but once you get the hang of it, winterizing your sand filter is just another part of the seasonal routine. It's all about removing the water and protecting the moving parts.
If you follow these steps, you can rest easy during those freezing January nights knowing your equipment is safe. When spring finally rolls around, you'll just have to put the plugs back in, hook up the hoses, and get back to what really matters—enjoying your pool. Stay warm out there!