How To Backwash A Filter

Look, I get it. You bought a pool or a fancy fish tank, and now you’re staring at a giant, grumpy-looking tube called a filter. You’ve heard whispers about “backwashing,” and it sounds like some kind of medieval plumbing torture. Relax. It’s actually the most satisfying chore you’ll do all week—like popping bubble wrap, but with water and dirt.

The Dirty Truth About Your Filter

Your filter’s job is to catch everything you don’t want: dead bugs, sunscreen slime, your neighbor’s shed hair. Eventually, it gets clogged, and water can’t flow. That’s when you backwash—you literally flip the flow backward to blast all that gunk out of the filter and into the ground (or a hose heading to your least favorite bush).

Fun fact: A backwashed filter expels water at up to 15 gallons per minute. That’s enough pressure to fire a garden hose into a small child’s face and still water your petunias in the same afternoon. You are now a water-pressure god.

Step One: Turn Off The Pump (Seriously)

Do not try to backwash with the pump running unless you enjoy pulling a soggy, screaming filter out of your ear canal. First, kill the power. Flip the switch. Unplug it. Stare at it menacingly to make sure it’s stopped. Water must be still—like a lake at dawn, not a washing machine on spin cycle.

I once knew a guy named Carl who skipped this step. He now has a permanent wave in his hair and a deep respect for pump impellers. Don’t be Carl.

Step Two: Locate The Secret Valve

Find the multiport valve—it’s the lumpy plastic dial near the filter with words like “Filter,” “Backwash,” and “Rinse.” It feels like a spaceship control panel for a 1986 Honda Civic. Turn the handle to “Backwash”—and only push down if it’s a push-pull model. Never force it. If it resists, you’re probably turning it the wrong way, which is fine. We all use screwdrivers as pry bars sometimes, but not today.

Pro tip: If your valve has a word you don’t recognize, like “Recirculate” or “Winterize,” just ignore it. That’s for people who own Instagram wellness accounts and use words like “aquascape.” You’re here to make the water dirty again, then clean it. Stay focused.

Backwash Sand Filter Procedure at Chelsea Pugliese blog

Step Three: Watch The Cloud Of Death

Now, turn the pump back on (yes, you turned it off, right?). A clear hose or sight glass will show you a horrifying, beautiful brown torrent. That’s all the skin flakes, algae, and backyard grudges your filter has been hoarding. Let it flow until the water runs clear—usually 2 to 3 minutes. You can whisper “be free, little nightmares” if you want. I do.

Surprising fact: A single backwash can eject over 200 gallons of water. That’s enough to fill a bathtub twice. You could theoretically swim in that dirty water. Please don’t. But also, you kind of just created a small, temporary mud puddle that will make your lawn look like a swamp for an hour. Your neighbors will judge you. Own it.

Step Four: Rinse (The Hero Nobody Wants)

After the brown water turns clear, turn the valve to “Rinse.” This is the boring but crucial part. Run the pump for about 30 seconds. It flushes out any leftover dirt that’s still trapped inside the filter’s delicate innards. Think of it as the “blow your nose, then wipe your nose” of pool care.

Without rinsing, you’ll pour that last blob of grime back into your pristine pool or tank, and your fish will judge you. Goldfish are excellent judges of character. They remember everything, especially that one time you skipped backwash for a whole month. They talk to the snails about it.

Pool Filter Rinse Vs Backwash: Essential Tips for Crystal Clear Water

Step Five: Return To Normal & Check Your Work

Finally, turn the valve back to “Filter.” Turn the pump on and watch the pool skimmer or tank outlet. You should see crystal-clear water flowing again. If you see a mushroom cloud of brown, congratulations—you forgot to rinse. Do not panic. Just repeat steps 2-4. We all mess up the first time.

Some experts say to backwash once a week for a pool, or when the pressure gauge jumps 10 psi. I say: do it when you remember, and if you forget, just tell your guests the green water is an “eco-friendly mineral aesthetic.” They’ll nod and avoid your pool. You’ll have the whole thing to yourself. Win-win.

One Last Warning

Never backwash into your neighbor’s yard unless their dog barks at 3 AM. Also, check local laws—some towns fine you for dumping pool backwash into the storm drain. They claim it’s “chlorine pollution.” I call it “government overreach.” But I don’t want you in handcuffs, so aim for a gravel patch or a drain that leads to a sewage line. Yeah, the same one your toilet uses. It’s weirdly poetic.

And remember: every time you backwash, you’re literally punting a colony of bacteria and dead skin into the great unknown. You are a sanitation superhero. Your filter is your sidekick. Now go blast some dirt into oblivion—and try not to get a face full of hose water. It tastes like regret and sunscreen.