Chemical Readings

This page explains each chemical reading in the PoolOps job form — what it measures, the normal range, and what happens if it's flagged.

Reading colours

After you enter a value, the field changes colour:

• Green — within the normal range. No action needed.
• Amber — borderline. Keep an eye on it and treat if trending the wrong way.
• Red — outside the normal range. This triggers a flagged reading on the admin side, so your manager can see it too.

Free Chlorine

Normal range: 1.0–3.0 ppm

Free chlorine is the active sanitiser in the water — it kills bacteria and algae. Too low and the pool isn't being sanitised effectively. Too high and it can irritate swimmers' skin and eyes. This is the reading you'll be adjusting most often.

Combined Chlorine

Normal range: 0–0.2 ppm (as close to 0 as possible)

Combined chlorine is chlorine that has already reacted with contaminants (sweat, sunscreen, etc.) and is no longer effective as a sanitiser. High combined chlorine produces that strong "chlorine smell" and can irritate eyes. If it's elevated, the pool needs shocking.

pH

Normal range: 7.2–7.6

pH measures how acidic or alkaline the water is. It's one of the most important readings — pH directly affects how well chlorine works. At pH above 7.6, chlorine becomes significantly less effective even if the level looks fine. Below 7.2, the water becomes corrosive and can irritate eyes and skin.

Total Alkalinity

Normal range: 80–120 ppm

Total alkalinity acts as a buffer for pH — it stops pH from swinging up and down rapidly. Low alkalinity makes pH unstable and hard to control. High alkalinity makes it difficult to adjust pH at all. Get alkalinity right first, and pH becomes much easier to manage.

Cyanuric Acid (Stabiliser)

Normal range: 30–50 ppm

Cyanuric acid protects chlorine from being broken down by UV sunlight. Without it, chlorine can dissipate within hours on a sunny NZ/AU day. Too much stabiliser, however, reduces chlorine's effectiveness — this is known as "chlorine lock". Stabiliser levels build up over time and are only reduced by diluting the pool with fresh water.

Salt (saltwater pools only)

Normal range: 2700–3400 ppm

Saltwater pools use a chlorinator that converts salt into chlorine. If the salt level is too low, the chlorinator can't produce enough chlorine. Too high and it can damage the chlorinator and equipment. This reading only appears for pools set up as saltwater.

Calcium Hardness

Normal range: 200–400 ppm

Calcium hardness measures how much dissolved calcium is in the water. Low calcium (soft water) is corrosive and will pull calcium from the pool shell and equipment — you'll see etching and pitting on concrete pools. High calcium causes scaling on surfaces and equipment. Calcium levels don't change quickly, so this reading typically only needs checking monthly.