Why Is My Pool Green? Handyman Answers for Homeowners Nationwide

Having a backyard pool should be relaxing. But when the water turns green? That’s a whole different story. Whether you’re in Arizona or Michigan that funky swamp look ruins the vibe fast— and it might even make your guests question your cleanliness.

As a handyman who’s seen it all, I’ve helped plenty of frustrated homeowners figure out what’s behind the green pool plague. Below, I’ll break down the causes, solutions, and prevention tips in a no-BS, easy-to-follow way. So let’s get into it.

Yes this might be on a Michigan – Detroit based site but this pool information for why my pool is green can be used for any pools nationwide. Many people ask Why Is My Pool Green?

First Things First: What Causes Green Pool Water?

You guessed it — algae. But the real question is why algae are thriving in your water in the first place.

Here are the top reasons your pool turned green:

1. Low Chlorine Levels

Algae can grow in just about any pool, but it absolutely thrives when there’s not enough chlorine to kill it. If your pool’s sanitizer level dips too low, even for a day or two, that’s an open invitation.

2. Poor Filtration

Got a pump that’s struggling? Dirty filter? Backwashing neglected? Filtration issues mean the water isn’t circulating or getting cleaned properly — another red carpet for algae.

3. pH and Alkalinity Out of Whack

If your water chemistry is off, chlorine doesn’t work as well. A high pH (above 7.6) or sky-high total alkalinity can basically disable your sanitizer. It’s like going into battle without your weapon.

4. Weather Conditions

Warm temperatures + lots of sunlight = algae buffet. If you’re in a humid state or having a heat wave, algae growth can go from mild to monstrous overnight — especially if your chemicals aren’t balanced.

Types of Algae (Yep, There’s More than One)

Not all green pools are the same. Here’s a quick breakdown:

• Green Algae – Most common. Usually floats in the water or sticks to walls. Easy to kill if you act fast.
• Yellow/Mustard Algae – Hangs out in shady areas, more resistant to chlorine. A pain in the ass.
• Black Algae – Toughest of the bunch. Grows in concrete and plaster pools. Root system embeds in walls. Requires aggressive scrubbing and strong treatments.

Step-by-Step: How to Fix a Green Pool

Step 1: Test the Water

Before you throw in a bucket of chlorine and hope for the best, test the water. You need to know where your levels are:

• Free chlorine
• pH
• Alkalinity
• Cyanuric acid (stabilizer)
• Phosphates (optional but helpful)

You can use test strips, a liquid test kit, or take a sample to your local pool store.

Step 2: Balance the Chemistry

Adjust your pH to between 7.2 and 7.6. This helps your chlorine work at full strength. You may need to add muriatic acid or sodium bisulfate to bring it down.

If your alkalinity is off, fix that too (aim for 80–120 ppm).

Step 3: Shock It Like You Mean It

Now it’s time to slam your pool with chlorine — this is what pool pros call a shock treatment.

Use calcium hypochlorite or a powerful non-stabilized chlorine and add 3 to 5 times the normal amount. Yep, it’s a lot. The goal is to raise your free chlorine level to 10+ ppm and burn out all the algae.

Important: Run your pump 24/7 during this process. No exceptions.

Step 4: Brush the Walls and Floor

Algae sticks to surfaces. After you shock, grab a stiff pool brush and get aggressive. Scrub walls, steps, ladders — even around the return jets. If you have black algae, use a wire brush (for concrete/plaster only).

Step 5: Run Your Filter Nonstop

Your filter is now your best friend. Let it run continuously until the water is clear. If it’s a sand or DE filter, backwash it daily. For cartridges, rinse them out often.

You may need to add flocculants or clarifier if the water stays cloudy. Just follow label directions and don’t overdo it.

How Long Will It Take to Clear Up?

Depending on how bad the algae are, it can take 2 to 5 days to fully clear the water. If your pool is deep green or blackish-green, expect a longer process and multiple shocks.

Stay consistent. Don’t skip filter cycles. Keep brushing. The water will turn milky blue before it turns crystal clear — that means you’re on the right track.

Can You Swim in a Green Pool?

Short answer: No.

Even if it looks “okay,” algae and bacteria can cause:

• Ear infections
• Skin rashes
• Pink eye
• Stomach problems

Not worth the risk. Wait until your water is blue and your chlorine is at safe levels.

When to Call a Handyman (Yep, Like Me)

You might be thinking: “Shouldn’t I be calling a pool guy?”
Sure, if you’ve got one. But here’s the deal:

As a handyman, I help homeowners troubleshoot, fix, and even prevent recurring pool problems — especially when they’re related to:

• Pool pump issues
• Electrical problems (like tripped breakers)
• Leaky plumbing lines or valves
• Broken timer boxes
• Deck repairs or coping issues

And yeah, sometimes folks just want someone to handle the mess so they don’t waste a summer weekend elbow-deep in chemicals.

Keeping Your Pool Blue All Season

Let’s talk prevention — because nobody wants to shock their pool every two weeks. If your a pool owner you never really want to ask why is my pool green? You just want to swim.

Weekly Pool Care Checklist:

• Test water 2–3 times a week (daily during heatwaves)
• Maintain 2–4 ppm of free chlorine
• Keep pH between 7.2 and 7.6
• Brush and skim once a week
• Vacuum weekly or as needed
• Run pump at least 8–12 hours a day in summer

Also, make sure your pool cover is clean, your deck isn’t full of debris, and your circulation system is working properly. Sometimes a small fix — like a clogged pump basket — can throw off the whole pool.

Want Me to Take a Look?

If you’ve tried everything and your pool is still green, or you’d rather have someone handle the dirty work, give me a call. I help homeowners across the country — especially in older homes where pool equipment might be outdated or neglected.

I’ll walk you through the problem, fix what needs fixing, and get you back to enjoying your backyard.