Water chemistry
Pool Chemistry Made Simple
You need a short list of chemistry readings, including calcium hardness, to keep the water clear.
You do not need a chemistry degree to keep a pool clear. You need a few chemistry readings, a reliable test kit, and a habit of checking the water before it gets away from you.
Here is the version we give Tidewater Care homeowners — without the jargon that makes people give up.
The tests that matter most
Free chlorine (or your sanitizer level)
This is what kills bacteria and algae. For most residential pools on chlorine, you are aiming for roughly 1–3 ppm free chlorine. Too low and the water goes dull or green. Too high and it smells sharp and irritates eyes. If you use a salt system, the cell generates chlorine — you still test free chlorine the same way.
pH
pH is how acidic or basic the water is. Ideal range is about 7.2–7.6. Low pH etches plaster and corrodes equipment. High pH reduces chlorine’s effectiveness and can cloud the water. pH drifts — especially after heavy rain or a big swim day — so it is worth checking often.
Total alkalinity
Alkalinity is the buffer that keeps pH from swinging wildly. Target is typically 80–120 ppm for most pools. When alkalinity is in range, pH is easier to hold. When it is not, you will chase pH every other day.
Cyanuric acid (stabilizer)
Cyanuric acid protects chlorine from being burned off by sunlight. In Virginia summers, that matters. Too little and chlorine disappears by afternoon. Too much and chlorine becomes sluggish. We aim for a moderate range and do not keep stacking stabilizer without testing.
Calcium hardness
Calcium hardness is how much dissolved calcium is in the water. For most plaster pools, a useful range is about 200–400 ppm. Too little and the water can etch the surface and wear on the equipment. Too much and scale shows up on the waterline, the heater, and a salt system if you have one. It does not swing as fast as chlorine or pH. Test it when you open, after a large refill, and about once a month during the swim season. Well water and some city water in Virginia can land outside that range, so test the water you use to fill up your pool.
A simple weekly rhythm
- Test free chlorine and pH at least twice a week in peak season.
- Test alkalinity and cyanuric acid weekly or every other week.
- Test calcium hardness when you open, after a refill, and about once a month.
- Adjust in small steps. Wait and retest. Do not dump product and walk away.
- After a storm or a heavy swim day, test the next morning.
What cloudy usually means
Cloudy water is almost never a mystery. It is usually one of: low sanitizer, high pH, poor filtration, or a filter that needs cleaning. Test first. Do not shock blindly. If the numbers look fine and the water is still dull, the filter or circulation is often the real issue.
When to call us
If you have adjusted chemistry twice and the water still will not clear, if you are seeing persistent algae, or if equipment is throwing error codes — that is when a visit earns its keep. Notes and photos after the stop mean you are not diagnosing alone.
Clear water is about consistency, it's not something you should have to battle after things get out of hand. Stay in front of it by testing regularly. Keep a test kit by the back door, check the chemistry levels as needed, and inquire about service if something will not settle.