CoachPoolUpdated: October 2026
What is the ideal pH for a pool?
The ideal pool pH is 7.2 to 7.6, with a target around 7.4. In this range chlorine works best and the water stays comfortable for eyes and skin.
Above 7.8, chlorine loses effectiveness and the water can turn cloudy or form scale. Below 7.0, the water becomes irritating and aggressive to equipment.
What chlorine level should a pool have?
For a private pool, aim for 1 to 3 ppm (mg/L) of free chlorine. With bromine, aim for 2 to 4 ppm. In a hot tub the water is warmer and heavily used: 3 to 5 ppm of chlorine or bromine is common.
Free chlorine is measured with test strips or a DPD kit. Too low and algae and bacteria take over; too high and it irritates swimmers and damages liners and equipment.
What is total alkalinity and what should it be?
Total alkalinity (TA) measures the water’s ability to hold a stable pH. Aim for 80 to 120 ppm.
If it is too low, pH swings with every addition; if it is too high, pH keeps drifting up and is hard to correct. Adjust alkalinity before pH.
What other readings should I watch?
Stabiliser (cyanuric acid) protects chlorine from sunlight: aim for 20 to 50 ppm outdoors. Much above that, chlorine becomes less effective.
Calcium hardness is ideally 100 to 300 ppm: too low and the water is aggressive, too high and it forms scale. If you have a salt system, set the salt level according to the manufacturer’s manual.
Why is my pool water green?
Green water is almost always algae: not enough chlorine, pH too high, too little filtration, or hot weather and storms.
What to do: 1) test and correct pH (7.2 to 7.4); 2) brush walls and floor; 3) shock with chlorine following the label; 4) run the filter continuously until the water clears; 5) clean or backwash the filter; 6) retest and restore your levels.
Why is my pool water cloudy or milky?
Cloudy water usually comes from poor filtration, a dirty filter, unbalanced pH or alkalinity, excess calcium, or weak sanitiser levels.
Check filtration first (run time, filter condition, pressure), then correct pH and alkalinity. A flocculant or clarifier can help remove fine particles, followed by cleaning the filter.
Work out your doses with CoachPool
Enter your readings: CoachPool checks the water balance and tells you what to add, step by step, with test and maintenance reminders. Free to start.
How do I shock a pool?
Shocking destroys algae, bacteria and chloramines. First adjust pH to 7.2 to 7.4, then add the shock dose shown on the package for your pool volume, ideally in the evening.
Keep the pump running without interruption. Do not swim until free chlorine has dropped below 3 ppm, often 12 to 24 hours later.
How many hours a day should I run the pump?
A handy rule: filtration hours = water temperature in °C divided by 2. At 24 °C (75 °F), that is about 12 hours a day. The warmer the water, the more you need to filter.
Run it during the hottest hours and, if possible, outside peak electricity rates. A variable-speed pump lowers energy use.
How often should I test the water?
In season, test pH and chlorine once or twice a week, and more often in a heat wave, after storms or heavy use. Check alkalinity and stabiliser once a month.
For a hot tub used regularly, test every 2 to 3 days, and before use if in doubt.
How do I lower or raise pH?
To lower pH, use a “pH minus” product (usually sodium bisulfate). To raise it, use a “pH plus” (usually sodium carbonate).
Add small doses following the label for your volume, with the pump running. Wait a few hours before retesting: it is better to correct in several steps than all at once.
How do I calculate pool volume?
Rectangular: length × width × average depth. Round: 0.785 × diameter × diameter × average depth. Oval or elliptical: 0.785 × length × width × average depth.
Average depth is the mean of the shallowest and deepest points. Cubic metres × 1,000 gives litres. Knowing your volume is essential for dosing products correctly.
Chlorine or bromine for a hot tub?
Bromine stays effective at high temperature and smells less; it suits hot tubs well. Chlorine is cheaper and widespread, but needs closer monitoring at 37 to 40 °C (100 to 104 °F).
Whichever you use, never mix them, keep pH between 7.2 and 7.6 and replace the tub water about every 3 months, depending on use.
Why does my pool smell strongly of chlorine?
A strong “chlorine” smell almost always comes from chloramines (combined chlorine), formed when chlorine reacts with sweat, lotions and impurities. It is not too much chlorine: it means the sanitiser is used up.
The fix is a shock treatment with good filtration, and encouraging swimmers to shower before getting in.
When and how should I winterize a pool?
Winterize when the water stays below about 12 °C (54 °F). Passive winterizing: lower the level below the skimmers, treat the water with a winterizing product, protect the pipes and cover the pool. Active winterizing: keep the filtration running at reduced hours, with a cover.
Either way, balance the water (pH, alkalinity) and clean the filter before closing the pool.
Can I swim right after treating the water?
After a pH corrector, wait until the product is well dispersed: a few hours of filtration. After shocking, wait until free chlorine has dropped below 3 ppm.
When in doubt, measure: free chlorine of 1 to 3 ppm and pH 7.2 to 7.6 are reassuring. Always follow the manufacturer’s instructions.
Can I do without chlorine?
There are alternatives or complements: salt electrolysis (which makes chlorine on site), bromine, active oxygen or UV. None fully replaces a residual sanitiser in a private pool.
What matters is keeping enough sanitiser, balanced pH and good filtration, whatever the system.
How often should I change hot tub water?
On average every 3 months, between 1 and 4 months depending on use: the hotter the water, the more people use it and the less it is refreshed, the faster it degrades.
Change it sooner if it stays cloudy despite treatment, foams constantly, or develops a lasting smell.
What temperature should a hot tub be?
Normal use is 36 to 38 °C (97 to 100 °F), and never above 40 °C (104 °F). Limit sessions to 15 to 30 minutes; frail people, pregnant women and children should ask for medical advice.
Between uses you can lower the temperature to save energy while keeping filtration running.
What water readings should a hot tub have?
Aim for pH 7.2 to 7.6, total alkalinity 80 to 120 ppm, calcium hardness 150 to 250 ppm and 3 to 5 ppm of sanitiser (chlorine or bromine).
At 37 to 40 °C the water is more sensitive: test more often than a pool, at least every 2 to 3 days with regular use.
Why is my hot tub water foamy?
Foam mostly comes from cosmetics, lotions, detergent left in swimsuits, or water overloaded with dissolved solids.
Shower before getting in, rinse swimsuits well, clean the filter, use an anti-foam as a stopgap and replace the water if it persists.
How do I clean a hot tub filter?
Rinse the cartridge with clean water every 1 to 2 weeks. About once a month, soak it in a hot tub filter cleaner, then rinse it thoroughly.
Replace it after about a year, sooner if it is damaged or no longer cleans up. Having two cartridges lets you alternate them.
How do I drain and clean a hot tub?
Before draining, run a hot tub plumbing cleaner through the system for about an hour. Switch off the power, drain the tub, then clean the shell with a hot tub cleaner (never a foaming household detergent) and rinse.
Refill, rebalance pH and alkalinity, then sanitise before heating again. Cleaning the plumbing at every water change limits biofilm and bad smells.
Work out your doses with CoachPool
Enter your readings: CoachPool checks the water balance and tells you what to add, step by step, with test and maintenance reminders. Free to start.