A green pool is one of the most common calls we get, especially after a hot stretch in Roseville, Sacramento, or Folsom. The good news: most green pools can be fixed without draining them. Below is exactly how to fix a green pool step by step, what causes it in the first place, and the signs that it’s time to hand it off to a pro.
Why pools turn green (especially in the Sacramento area)
Green water is algae, and algae grows when there isn’t enough chlorine in the pool to keep it in check. A few things make that easy to happen around here:
- Summer heat. Sacramento Valley summers regularly top 100°F, and warm water is exactly what algae loves.
- Strong sun. UV light burns off chlorine fast, especially in the afternoon.
- Too much stabilizer. Chlorine tablets (pucks) add cyanuric acid (CYA) every time they dissolve. Over a long season, CYA builds up and makes your chlorine far less effective, even when a test says chlorine is present.
- Equipment problems. A pump that doesn’t run long enough, a dirty filter, or a broken timer lets water sit and turn.
- Storms, pollen, and time away. A windstorm full of debris or a week of vacation without care can tip a pool over the edge.
What you’ll need
- A good test kit that measures free chlorine, pH, and cyanuric acid (test strips only give rough readings)
- Liquid chlorine, or a calcium hypochlorite (cal-hypo) shock
- pH decreaser, if your pH is high
- A pool brush, leaf net, and vacuum
- Gloves and eye protection
How to fix a green pool in 7 steps
1. Test the water
Before adding anything, test free chlorine, pH, and cyanuric acid (CYA). The CYA number matters most. If it’s very high (roughly 80 ppm or more), chlorine struggles to kill algae, and you may need to replace some of the water before shocking will work. Most local pool stores will test a water sample for free if you don’t have a good kit.
2. Clear out leaves and debris
Skim the surface, empty the skimmer and pump baskets, and net out as much as you can from the floor. Leaves and debris soak up chlorine that should be going after the algae.
3. Balance the pH
Chlorine works best when pH is between 7.2 and 7.6. If yours is higher, lower it with a pH decreaser before you shock. Follow the product label, and add it slowly near a return jet with the pump running.
4. Shock the pool, and keep it shocked
This is where most DIY attempts fall short. One bag of shock is rarely enough for a green pool. You need to raise the chlorine to a high level and hold it there, retesting and adding more several times a day until the algae is gone. How high depends on your CYA: the more stabilizer in the water, the more chlorine it takes. Liquid chlorine is usually the best choice because it doesn’t add more stabilizer the way tablets and some bagged shocks do.
Safety first: never mix pool chemicals together or pour them into the same bucket, always add chemicals to water (not water to chemicals), and keep everyone out of the pool until chlorine drops back to a normal level.
5. Brush every surface
Brush the walls, floor, steps, and behind ladders at least once a day. Brushing breaks up algae so the chlorine can reach it and keeps it from hiding in corners.
6. Run the pump nonstop and clean the filter
Run your pump 24 hours a day until the water is clear. Dead algae clogs filters quickly, so watch your pressure gauge and clean or backwash the filter when pressure rises about 8 to 10 psi above its clean reading. Expect to do this more than once.
7. Vacuum and rebalance
As the water goes from green to cloudy blue to clear, dead algae settles on the floor as a gray or white dust. Vacuum it up (to waste, if your filter has that setting) so it doesn’t cloud the water again. Once the water is clear and holds its chlorine overnight, rebalance pH, alkalinity, and calcium, and return to a normal chlorine level.
How long does it take to clear a green pool?
Most green pools clear in 3 to 7 days when they’re kept at shock level the whole time. A light green pool can turn around in a day or two. A dark green or black swamp can take a week or more, especially if the stabilizer is high or the filter can’t keep up. If you’re not seeing steady progress after a few days, something is usually holding it back: high CYA, a filter problem, or not enough chlorine.
When to call a pro instead
DIY works well for a pool that’s just starting to turn. It’s time to call a professional if:
- You can’t see the bottom of the deep end
- Your stabilizer (CYA) is high and some water needs to be drained and refilled
- The pump, filter, or other equipment isn’t working right
- You’ve been at it for a week and the water keeps going back and forth
- You’re selling the home, hosting an event, or need it done fast
- You’d rather not handle gallons of chlorine and acid yourself
One more tip: avoid fully draining a pool on your own. Emptying a pool at the wrong time can damage the plaster or liner, and in some conditions groundwater can even push the pool shell up out of the ground. A pro will know when a partial drain makes sense and how to do it safely.
Our green-to-clean service
Green pools are one of our specialties. With our green pool cleanup service, we shock, brush, filter, and balance the water back to clear, swimmable condition, often in just a few days. We handle the chemicals, the equipment checks, and the cleanup, so you don’t have to. Here’s a real one we did:
The Goods Pool Service is a licensed pool contractor (CA Lic. #1145343) serving homes and properties within 25 miles of Roseville, including Rocklin, Granite Bay, Folsom, El Dorado Hills, Sacramento, and Citrus Heights. If the problem turns out to be a failing pump or filter, we also handle pool equipment repair and upgrades.
How to keep your pool from turning green again
The best fix for a green pool is never getting one. A few habits go a long way:
- Keep free chlorine steady instead of letting it drop and then shocking
- Test the water at least once a week, and more often in summer
- Run the pump longer during hot months
- Keep an eye on stabilizer if you use chlorine tablets
- Clean the filter and brush the pool regularly
Or skip the chores entirely. Our monthly pool service starts at $155 and keeps your water balanced and clear all year. Curious what it would cost for your pool? Here’s a breakdown of how much pool service costs in the Sacramento area.
Green pool FAQs
Can you swim in a green pool?
No. Algae can harbor bacteria, and murky water makes it hard to see someone below the surface. Wait until the water is clear and chlorine is back to a normal level.
Should I drain a green pool?
Usually not. Most green pools can be cleared with chemicals, brushing, and filtration. Draining only makes sense in specific cases, like very high stabilizer, and it’s a job best left to a pro.
Why did my pool turn green overnight?
It usually wasn’t really overnight. Chlorine had most likely been dropping for days, and a hot day or a storm pushed it over the edge. It can also happen fast if the pump stops running.
Why is my pool still cloudy after shocking?
Cloudy water after shocking is normal. That’s dead algae. Keep the pump running, keep chlorine at shock level, clean the filter, and vacuum. It should clear over the next day or two.
How much does it cost to fix a green pool?
It depends on how green the pool is, how big it is, and whether any equipment needs work. The fastest way to find out is to text us a photo of your pool at 916-534-0561 for a quick quote.
Pool turned green? Text us a photo.
Send a photo of your pool to 916-534-0561 and we’ll get you a fast quote. Same-week service is available Monday through Friday, 9am to 7pm.