Cloudy Pool After Rain? Here’s What’s Happening and How to Fix It

You step outside after a heavy rainstorm. The sky is clear again. The garden looks great. Then you walk over to your pool and the water is cloudy, dull, maybe even a little green. It happens to a lot of pool owners. And it always seems to appear right when you want to swim.

The good news is this is fixable. You just need to understand what rain actually does to pool water, what to test first, and what mistakes to avoid while you’re sorting it out.

What to Test First

Before you add anything to your pool, test the water. Adding chemicals without testing first is one of the most common mistakes pool owners make after a storm. You can end up wasting product or making the imbalance worse.

Test for:

pH (target: 7.2 to 7.6)
Total alkalinity (target: 80 to 120 ppm)
Free chlorine (target: 1 to 3 ppm)
Calcium hardness (target: 200 to 400 ppm)
Phosphates (ideally under 500 ppb)

Use a proper test kit or take a sample to your local pool shop. Test strips give you a rough guide but a full water test gives you more accurate numbers to work from.

How to Fix a Cloudy Pool After Rain

Step 1: Remove Debris First

Before you touch chemicals, clean out the physical mess:

Skim the surface to remove leaves and debris
Check and empty your skimmer basket
Give the pool walls and floor a quick brush to loosen anything sitting on the surfaces

The cleaner the water is to start with, the more effectively your chemicals will work.

Step 2: Check Your Water Level

If the pool is sitting well above the midpoint of the skimmer opening, lower the water level before doing anything else. You can do this by:

Setting your multiport valve to the waste setting and running the pump
Using a submersible pump

Getting the level right means your skimmer works properly and your chemicals don’t get further diluted.

Step 3: Fix Alkalinity Before pH

Always fix alkalinity before you try to adjust pH. Alkalinity is the foundation. If it’s low, your pH will keep drifting no matter what you add.

Use sodium bicarbonate (baking soda) to bring alkalinity back up into the 80 to 120 ppm range
Follow the dosing guide on the product for your pool size
Wait a few hours after adding it, then retest before moving on

Step 4: Adjust the pH

Once alkalinity is back in range, check your pH again. It may have come up on its own or it may still need adjustment.

Use pH increaser (sodium carbonate) to raise it
Use pH reducer (dry acid or muriatic acid) to bring it down
Get it sitting between 7.2 and 7.6 before you add chlorine

This order matters. Chlorine works best at the right pH. If you shock while pH is still out of range, you’ll waste a lot of the treatment.

Step 5: Shock the Pool

After rain, a shock treatment is almost always needed. Even if your chlorine reading doesn’t look too bad, the water has been through a lot and needs a strong dose to deal with everything in it.

Use a quality chlorine shock and follow the label instructions for your pool size
Most pool recovery situations call for raising free chlorine up to around 10 ppm to oxidise contaminants and knock out any early algae growth
Shock in the evening if you can, as sunlight breaks down chlorine fast and doing it at night gives the shock time to work before UV exposure starts the next morning

Step 6: Run the Filter Continuously

After shocking, run your filter without stopping:

Keep the water circulating so the filter can catch dead algae, fine particles, and debris
Run it for at least 24 hours without interruption
Check the water after and keep going if it’s still not clear
Clean or backwash the filter during this time if it slows down or gets blocked

Step 7: Deal With Phosphates

Once the water is looking clearer and your chemistry is balanced, address phosphates.

Use a phosphate remover product according to the instructions
It will temporarily make your pool look cloudy again as it binds to the phosphates and turns them into solid particles your filter can catch
This cloudiness is normal and should clear within a day or two with the filter running
Don’t add a phosphate remover while the pool is still green or heavily cloudy from algae. Get the chlorine right and clear the algae first, then tackle phosphates separately

Step 8: Use a Clarifier If Needed

If the water is still hazy after 48 hours, a pool clarifier can help speed things up:

Clarifiers work by clumping tiny suspended particles together so your filter can catch them more easily
Add the clarifier after your chemicals are balanced and keep the filter running
It’s not a replacement for proper chemistry but it can get you to clear water a bit faster in the final stages

What to Stop Doing After Rain

Don’t swim in cloudy water. Cloudy water after rain often has elevated bacteria levels. Until the water is balanced and clear, stay out.
Don’t add chemicals without testing first. If your pH is way off, the shock won’t work properly anyway. Test, then treat.
Don’t wait too long to deal with it. The longer you leave it, the more time algae has to settle in. A simple chemistry fix can turn into a days-long algae treatment if you ignore it.
Don’t turn the pump off. After shocking, leaving the pump off overnight lets dead material float around in the water and slows the whole clearing process. Keep the filter running.
Don’t reach for algaecide as your first move. If algae is already growing, chlorine is what kills it. Algaecide is a preventive tool. Balance your chemicals and shock first.

How to Get Ahead of It Before a Storm

Boost your chlorine slightly. If rain is forecast, give your chlorine a small top-up beforehand. This builds a reserve so when the storm brings in organic material, there’s more chlorine ready to handle it.
Check your pH and alkalinity. Aim to have both sitting in the middle of their ideal ranges before the storm hits, not at the edges. This gives you a buffer so if rain pushes them down, they don’t fall as far out of range.
Add algaecide as a preventive step. Adding algaecide before a storm gives your water extra protection against the algae spores that rain will wash in. It’s much easier to prevent algae than to treat it.
Lower the water level a little. If heavy rain is forecast, lower your water level by a few centimetres beforehand. This gives the pool room to absorb the rain without the water level rising above the skimmer.
Shut off electrical equipment. Turn off pumps, heaters, and other connected equipment before a bad storm. Our post on storm-proofing your pool covers the full pre-storm routine in detail.

The Short Version

Cloudy pool water after rain is common. It doesn’t mean something is seriously wrong. It means the water chemistry took a hit from the storm and needs attention.

Act quickly, test before adding anything, fix alkalinity and pH first, shock the pool, and keep the filter running throughout. Follow that order and the water should come good within a day or two. If your pool has been through a lot of rough weather recently and is starting to show it, the pool renovation checklist is a good place to start thinking about what needs attention.