Your pool is a giant bowl of soup. Honestly, that’s the best way to look at it. Without a high-quality pool filter inground pool setups quickly turn into a science project featuring algae, sunscreen slick, and whatever the neighborhood birds left behind. Most people just buy whatever the builder recommends. That is usually a mistake. Builders like what’s easy to install, not necessarily what’s easiest for you to clean on a 100-degree Sunday in July.
Let's get real. Nobody actually wants to talk about filtration. It's boring. But you know what's worse? Spending three hours scrubbing green slime off a pebble-tec finish because your filter couldn't keep up with a light rainstorm.
The Dirty Truth About Micron Ratings
Micron ratings are the "thread count" of the pool world. Everyone brags about them, but half the people don't know what they mean. A micron is a unit of measurement—one-millionth of a meter. For context, a human hair is about 50 to 70 microns wide.
If you choose a sand filter, you’re looking at catching stuff down to about 20 or 40 microns. That sounds okay until you realize that standard pool algae can be as small as 5 to 10 microns. You see the problem? Your filter is literally letting the enemy swim right through the lines. Cartridge filters get you down to about 10 or 15 microns. If you want the "crystal clear" look that looks like your water is actually invisible, you go with Diatomaceous Earth (DE). Those bad boys catch particles as small as 2 to 5 microns. It’s basically a nightclub bouncer that won’t even let a dust mite in without an ID.
But here is the trade-off. DE filters are a massive pain. You have to handle white powder that looks like something out of a 1980s Miami movie, and you can’t just wash it down the storm drain in many cities like Los Angeles or Austin because it clogs up the works.
Why Your Pool Filter Inground Pool Needs Are Different
Inground pools aren't like those pop-up rings you buy at a big-box store. They have massive volumes of water—often 15,000 to 30,000 gallons—and they are deep. Depth means pressure.
When you’re looking at a pool filter inground pool installation, you have to consider the "turnover rate." The goal is to move every single drop of water through that filter at least once a day. If you have a pump that’s too strong for a small filter, you’ll actually blow a hole through the filter media. Or, even worse, the pressure will skyrocket and your pump will burn out early. It's a delicate dance between the flow rate of the pump and the square footage of the filter.
Sand Filters: The Old Reliable (Mostly)
Sand is the "set it and forget it" option. Kind of. You backwash it, which basically means you run the water backward to flush out the junk. It’s easy. But sand filters are heavy. Like, "don't try to move this alone" heavy. After about five to seven years, that sand gets "channeled." This is a fancy way of saying the water has carved a permanent path through the sand, so it’s not actually being filtered anymore. It just slides right through the gaps.
If you're noticing your pool stays cloudy no matter how much chlorine you dump in, your sand is probably dead. You can try a "deep clean" with specialized chemicals, but usually, you just need to swap the media. Some people are switching to glass media now. It’s more expensive than sand, but it lasts longer and filters better.
Cartridge Filters: The Modern Favorite
Most new builds in places like Florida or Arizona are going with large-capacity cartridge filters. Why? No backwashing. This is huge if you live in a drought-prone area where wasting 200 gallons of water just to clean a filter is basically a crime.
With a cartridge, you just pull the pleated filters out and hose them down. It’s messy. You will get wet. Your shoes will be soaked. But you can see exactly what you're cleaning out of your pool. Pro tip: keep a second set of cartridges on hand. That way, you can pop the clean ones in and clean the dirty ones whenever you feel like it, rather than rushing to finish before the sun goes down.
Sizing Secrets the Salesman Won't Tell You
Go big. Seriously.
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If the chart says you need a 200-square-foot filter, buy the 400-square-foot one. In the world of pool filter inground pool equipment, over-sizing is a superpower. A larger filter has more surface area. More surface area means it takes longer for the "pores" to get clogged. This leads to lower system pressure, which saves your pump, and it means you might only have to clean the filter twice a year instead of every month.
It’s an upfront cost that pays for itself in avoided headaches.
Think about it like this. Would you rather have a tiny trash can you have to empty every single day, or a big one you empty once a week? It’s the same logic.
The Algae Loophole
Let's talk about the "dead algae" problem. This is where most people lose their minds. You shock the pool. The algae dies. The water turns from green to a weird, milky white. You run the filter for 24 hours. Nothing happens. Still cloudy.
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This happens because dead algae is often too small for sand or even some cartridge filters to grab. It just keeps circulating. To fix this, you need a "flocculant" or a "coagulant." These chemicals act like a magnet. They clump those tiny particles together into big chunks that the filter can finally catch. If you have a sand filter, you can also add a little bit of DE powder (about a cup) through the skimmer. It coats the top of the sand and helps it catch the smaller stuff. Just watch your pressure gauge like a hawk, because it will spike fast.
Maintenance Reality Check
- Pressure Gauges: If your gauge doesn't move when you turn the pump off, it’s broken. Buy a new one. They cost ten bucks and save you thousands in repairs.
- The O-Ring: Every time you open that filter, check the big rubber O-ring. If it’s dry, it’ll leak air. Use a silicone-based lubricant. Never use Vaseline—it’s petroleum-based and it will eat the rubber.
- Air Bleeding: When you turn the system back on after cleaning, you have to let the air out of the top. If you don't, that trapped air can turn your filter tank into a literal projectile if the pressure gets too high. There have been documented cases of filter lids blowing through roofs. Don't be that guy.
The Cost of Neglect
Ignoring your pool filter inground pool system is the fastest way to kill your backyard vibe. A clogged filter makes the pump work harder. A harder-working pump pulls more amps. More amps mean a higher electricity bill. You’re literally paying more money to have a dirtier pool. It’s a losing game.
Most experts, including those from the Pool & Hot Tub Alliance (PHTA), suggest a full teardown and internal inspection at least once a year. Even if things seem fine, the internal manifolds or "laterals" can crack. A cracked lateral in a sand filter will start spitting sand back into your pool. You’ll see little piles of it near the return jets. If you see that, the party’s over until you take the whole thing apart.
Actionable Next Steps for a Clear Pool
Stop guessing. If your pool water doesn't look like bottled water, your filtration is failing.
First, check your pressure gauge. Note the "clean" pressure after a wash. Once it rises 8 to 10 PSI above that mark, it’s time to clean. Don't wait until the water flow at the jets feels weak. By then, the damage is already being done to your pump's seals.
Second, if you’re still using an old-school sand filter and hate the water quality, look into "ZeoSand" or glass media. It’s an easy swap that doesn't require replacing the whole tank, and it’ll get you closer to that DE-level clarity without the DE-level hassle.
Finally, ensure your pump run-time is sufficient. In the summer, you should be running that pump for at least 8 to 12 hours. If you have a variable-speed pump, run it longer at a lower speed. It’s quieter, cheaper, and gives the filter more time to do its job. A slow, steady filter always beats a fast, turbulent one.
Check your filter's O-ring today for cracks. A five-minute inspection now prevents a flooded equipment pad tomorrow. Keep the chemicals balanced, but remember: chlorine kills the junk, but the filter is what actually removes it from your life. One can't work without the other.