The essentials in 30 seconds
Keep free chlorine at least 1 ppm (the CDC gives 1 to 4 ppm as the typical range for chlorine pools) and pH between 7.0 and 7.8. If you use stabilized chlorine (cyanuric acid, dichlor or trichlor), keep free chlorine at least 2 ppm. The CDC advises testing at least twice a day, and more often when the pool is busy. Each week, skim, empty the baskets, brush the walls, vacuum the floor and check the filter. Pool chemicals send about 4,500 people a year to US emergency departments, over a third of them children or teens: store them apart, add chemical to water, never water to chemical, and never mix products.
- Green water means the chlorine lost the battle: test, correct pH, shock by the label, brush and filter around the clock.
- A home pool needs layers of protection for children: a fence of at least 4 feet on all sides, a self-closing, self-latching gate and constant supervision.
- Anyone who has had diarrhea should stay out of the pool.
Pool maintenance schedule: what to do and how often
| How often | Task | Why |
|---|---|---|
| Daily (twice a day per CDC) | Test free chlorine and pH | Sun, sweat, urine and heavy use burn chlorine quickly |
| Daily or as needed | Skim leaves and debris from the surface | Organic matter uses up chlorine and clogs the skimmer |
| Whenever they fill, at least weekly | Empty the skimmer and pump baskets | Full baskets slow circulation and strain the pump |
| Weekly | Brush walls, steps and the waterline | Loosens algae and biofilm before they take hold |
| Weekly | Vacuum the floor | Removes settled dirt the filter cannot reach |
| Weekly | Check the filter pressure gauge | A rise over the clean reading means the filter needs cleaning |
| As the manufacturer directs | Backwash a sand or DE filter, or rinse a cartridge | Restores flow and filtration |
| After storms or parties | Test, skim, and shock if needed | Rain and many swimmers lower chlorine fast |
| As your kit or pool professional advises | Check alkalinity, calcium hardness and stabilizer with a fuller test kit | Helps keep pH steady and the water balanced |
The routine, step by step
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01
Skim the surface
Use a leaf net before debris sinks. It is the fastest way to keep the filter and chlorine working.
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02
Empty the baskets
Turn the pump off first, then clear the skimmer basket and the pump strainer basket.
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03
Brush
Work from the waterline down toward the main drain, so dirt drifts where the filter can catch it. Give corners, steps and shady spots extra attention; algae starts there.
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04
Vacuum
Use a manual vacuum or an automatic cleaner. Vacuum slowly so you do not stir dirt back into the water.
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05
Check the filter
Note the clean pressure reading after each filter cleaning. When the gauge climbs noticeably above it, or flow drops, clean or backwash as the manufacturer directs.
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06
Test and adjust
Test after cleaning, correct pH first, then chlorine, and add products one at a time with the pump running.
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07
Clean the waterline
Wipe the tile line with a pool-safe cleaner to remove the scum of sunscreen and body oils.
Pool chemistry basics: chlorine, pH and testing
Chlorine is what kills germs. pH decides how well it works: the CDC says chlorine loses effectiveness above pH 8.0, and below 7.0 pipes and equipment are more likely to corrode, while water outside the range irritates skin and eyes.
| Measure | Target | Notes |
|---|---|---|
| Free chlorine, pool | At least 1 ppm; typically 1 to 4 ppm | Follow your product's label |
| Free chlorine, pool with cyanuric acid (stabilizer) | At least 2 ppm | Stabilizer slows disinfection |
| Bromine | Typically 3 to 8 ppm | Used mostly in hot tubs |
| Free chlorine, hot tub | At least 3 ppm | CDC advises against stabilizer in hot tubs |
| pH | 7.0 to 7.8 | Chlorine weakens above 8.0 |
| Testing | At least twice a day | More often with heavy use |
Choosing a test kit
The CDC rates a DPD test kit as the most accurate home method and test strips as less accurate. Very high chlorine, above about 10 ppm (right after shocking, for example), can bleach a DPD test and show a false low or zero reading, so dilute the sample or use a high-range test.
Why chlorine matters: germs and recreational water illnesses
Swimmers can catch diarrhea, skin rashes, ear infections and respiratory illness from contaminated water, which the CDC groups as recreational water illnesses. Most germs die within minutes at the right chlorine level, but not all:
| Germ | Time to kill |
|---|---|
| E. coli O157:H7 | Under 1 minute |
| Hepatitis A virus | About 16 minutes |
| Giardia | About 45 minutes |
| Cryptosporidium (Crypto) | About 10.6 days |
That is why the swimmer habits matter as much as the chemicals:
- Stay out of the water with diarrhea; one incident can release millions of germs.
- Shower for at least 1 minute before swimming.
- Do not swallow pool water, and do not pee or poop in it.
- Take children on bathroom breaks and check swim diapers every hour, changing them away from the poolside.
- If there is poop or vomit in the pool, get everyone out and follow the CDC's contamination response guidance before anyone swims again.
How to shock a pool safely
Shocking (superchlorination, as it is often called in the UK) means raising chlorine well above normal for a short time to burn off contaminants and kill algae. Do it after heavy use, after a storm, when the water smells strongly of chlorine or looks dull, and when algae appears.
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01
Test first
Bring pH into range before you shock; chlorine works poorly at high pH.
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02
Read the label
Dose by your pool's volume and the product's directions. Calculate the volume once and write it down.
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03
Dress for it
Goggles, gloves and a mask; open the container outdoors, upwind.
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04
Pre-dissolve only if the label says so
Fill a clean bucket with pool water first, then add the product to the water.
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05
Add it with the pump running
Pour slowly around the edge or in front of a return jet. Never add two products at the same time.
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06
Do it in the evening
Sunlight breaks down chlorine, so shock works longer after sunset.
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07
Keep swimmers out
Injuries happen when chemicals are added just before someone gets in. Wait until a test shows free chlorine back in the normal range.
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08
Rinse and store
Rinse the bucket, close the container tightly and put it back in its own place.
How to clear a green or cloudy pool
Green water is algae, and it usually appears when chlorine drops too low for a few days, the filter has not run long enough, or both. Cloudy water usually means poor filtration, unbalanced water, or a chlorine level that is too low.
| What you see | Likely cause | What to do |
|---|---|---|
| Green, murky water | Algae after low chlorine | The recovery plan below |
| Green walls or corners, clear water | Algae starting in low-circulation spots | Brush hard, shock, check return jets point to move water |
| Cloudy, dull water | Weak filtration, high pH, low chlorine | Test and correct pH and chlorine; clean the filter; run it longer |
| Strong chlorine smell, red eyes | Chlorine used up by contaminants, or pH out of range | Test; shock if free chlorine is low; correct pH |
| Brown or rusty tint | Metals in the water | Test for metals; ask a pool professional before shocking |
| Low flow at the returns | Full baskets or a dirty filter | Empty baskets; clean or backwash the filter |
| Sudden cloudiness after a party or storm | Contaminants and debris | Skim, vacuum, test and shock |
Green pool recovery plan
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01
Keep everyone out
If you cannot see the floor, you cannot see a swimmer in trouble.
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02
Clear the debris
Skim leaves and empty both baskets.
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03
Test and correct pH
Bring it into the 7.0 to 7.8 range first.
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04
Shock by the label
Use the dose the label gives for algae. Very green water may need more than one treatment.
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05
Brush everything
Walls, floor, steps and behind ladders, to break up algae so chlorine can reach it.
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06
Filter around the clock
Run the pump continuously until the water clears, cleaning or backwashing the filter as the pressure rises; it will clog fast with dead algae.
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07
Vacuum the dead algae
Once it settles as a gray-brown layer, vacuum it out, to waste if your filter allows.
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08
Retest daily
Keep chlorine up until the water is clear and a test shows normal levels, then return to the weekly routine.
If the water stays green after several days, the filter may be damaged, circulation poor, or the stabilizer level too high. A pool service can test the full chemistry and inspect the equipment.
Pool safety for children
The CDC lists drowning as the leading cause of death for children aged 1 to 4, and the federal Pool Safely campaign says this age group is the most susceptible to fatal drowning. Drowning is quick and silent. Build layers of protection:
- A non-climbable fence at least 4 feet high around all sides of the pool, separating it from the house.
- A self-closing, self-latching gate as the only way in.
- Alarms on doors from the house to the pool area, and locks or alarms on windows.
- Covers kept in working order, and the pool covered when not in use.
- Constant, close supervision by an adult who is not distracted, swimming lessons, life jackets approved by the US Coast Guard and CPR training for the adults in the house.
- Pool chemicals locked away where children cannot reach them.
Opening and closing the pool for the season
At opening, clear the cover before removing it, top up the water, clean the baskets and filter, run the pump, then test and balance pH before you shock. At closing, follow your equipment manufacturer's winterizing steps for your climate, balance the water first, and store chemicals safely over the off-season, away from heat and from each other.
Pool cleaning: frequently asked questions
How often should I clean my pool?
Skim and test daily in season, empty the baskets a few times a week, and brush and vacuum weekly. Clean the filter whenever the pressure rises.
What should chlorine and pH be in a pool?
The CDC says free chlorine at least 1 ppm, typically 1 to 4 ppm, and pH between 7.0 and 7.8. With stabilizer, keep free chlorine at least 2 ppm.
Why is my pool green?
Algae, usually after chlorine dropped too low or the filter did not run long enough. Correct pH, shock, brush and filter continuously.
How long after shocking can you swim?
When a test shows free chlorine back in the normal range. Follow the product label.
Why is my pool cloudy?
Usually weak filtration, high pH or low chlorine. Test the water, clean the filter and run it longer.
Can you mix pool chemicals?
No. Mixing products, especially chlorine and acid, can release toxic gas. Add one product at a time, chemical to water.
Do I need to test my pool every day?
The CDC advises testing at least twice a day, and more often when the pool is busy. A DPD kit is the most accurate.
Can I swim in a green pool?
No. Germs may be present and you cannot see swimmers below the surface. Clear the water first.
Sources
Official health and safety guidance, checked on 27 October 2026.
- CDC · Home pool and hot tub water treatment and testing ↗pH 7.0 to 7.8, minimum free chlorine for pools, hot tubs and stabilized pools, testing frequency, DPD kits and strips, germ kill times.
- CDC · Guidelines for keeping your pool safe and healthy ↗Typical chlorine and bromine ranges, chemical safety gear, 4,500 emergency visits a year, drowning in children aged 1 to 4, swimmer hygiene, Crypto survival.
- CDC MMWR · Pool chemical injuries in public and residential settings, 2008–2017 ↗Inhalation as the top diagnosis, chemical to water, pre-dissolving, never mixing chlorine and acid, injuries when chemicals are added just before swimming.
- CDC · Pool chemical safety ↗Storage below 95 °F, dry, separate and labeled, secured from children and animals, ventilation.
- CPSC Pool Safely · Install proper barriers, covers and alarms ↗4-foot non-climbable fence on all sides, self-closing self-latching gates, door alarms, covers, children aged 1 to 4.
Opening the pool this weekend?
Test pH and chlorine before anything else, and check the gate latches itself shut before the first swim.