What gets read on every visit
Water temperature, free chlorine, combined chlorine, total chlorine, pH, total alkalinity, calcium hardness, cyanuric acid, phosphates, iron, and copper. Salt where the pool has a cell.
Temperature is not filler — it moves LSI on its own, which is why a pool balanced in August can turn aggressive in January with nobody touching a chemical.
Combined chlorine is the number nobody reads
Free chlorine is the chlorine still available to work. Combined chlorine is what is already used up and bound to sweat, sunscreen, and organics — it is the chemical that smells like a public pool, burns eyes, and does almost nothing.
Total chlorine is the two added together. When your total reads fine and your pool still feels off, the split between free and combined is the reason, and it only shows up if somebody actually tests for it.
Phosphates: algae food
Phosphates get into a pool from fill water, fertilizer runoff, leaves, soap, and some scale and stain products. They do not hurt anyone, and they are not an emergency at low levels.
But at high levels they feed algae, and you end up burning chlorine week after week to hold a pool that keeps wanting to turn. When the number is high enough to matter, a phosphate remover is cheaper than the chlorine you would otherwise pour in all summer.
Iron and copper: where stains come from
Iron shows up in well water and older plumbing and stains rust-brown. Copper comes from heater exchangers, some algaecides, and low-pH water eating at metal, and it stains blue-green or turns blonde hair a color nobody asked for.
Metals do not filter out. They either stay dissolved and controlled with a sequestrant, or they fall out onto your plaster and become a stain that takes acid work to remove. Catching a metal reading before it stains is the whole game.
What is included and what is extra
Weekly service includes the chemicals a normal pool uses: chlorine, acid, and sodium bicarbonate, in whatever amount the water asks for. There is no per-gallon surprise in July.
Phosphate removers and metal sequestrants are specialty treatments, not routine chemistry, and they are priced separately — you will see the reading, the recommendation, and the cost before anything is added. If your pool needs them regularly, they can be folded into a higher monthly rate so it is one predictable number instead of an occasional line item.
