Pool water balance: How to raise or lower pH and alkalinity

Your pool’s pH should sit between 7.2 and 7.6, and total alkalinity between 80 and 120 ppm. If either is out of range, chlorine works less effectively, swimmers get sore eyes and itchy skin, and your pool surfaces and equipment wear faster. Here’s how to fix each reading, and what the rest of a test result means.

How do I raise, increase, or lower pH in my pool?

Pool pH should be between 7.2 and 7.6. pH measures how acidic or alkaline the water is, and it decides how well your chlorine works.

• If pH is too high (above 7.6): Add pool acid to bring it down. Liquid hydrochloric acid and dry acid are the two common options. High pH makes chlorine sluggish, leaves water cloudy, and builds scale on surfaces.
• If pH is too low (below 7.2): Add a pH increaser like soda ash (sodium carbonate) when learning how to increase pH in pool water. Low pH makes water corrosive – damaging metal fittings, equipment, and pool surfaces – while stinging swimmers’ eyes.

If you have a salt chlorinator, expect pH to creep upwards over time. That is normal for salt pools, which is why salt pool owners usually add acid more often than anything else. If keeping pH in range is a constant battle, an automatic pH controller can manage it for you.

How much to add depends on your pool volume and how far out the reading is. Follow the product label or bring a water sample into our Claremont store and we will calculate exact dosages with you.

How do I raise, increase, or lower alkalinity in my pool?

Total alkalinity should be between 80 and 120 ppm. Alkalinity acts as a buffer for pH: it stops pH swinging up and down every time it rains, the pool gets busy, or you add chemicals.

• If alkalinity is too low (below 80 ppm): Add an alkalinity increaser, usually sodium bicarbonate (buffer), when looking at how to raise alkalinity in pool water. With low alkalinity, pH becomes unstable and hard to hold in range.
• If alkalinity is too high (above 120 ppm): Add acid in small amounts over several days with the pump running. Acid lowers both alkalinity and pH, so pH will drop too. Running water features or spa jets to agitate the surface helps bring pH back up while alkalinity stays down. High alkalinity makes pH stubbornly hard to lower and can lead to cloudy water and scale.

What’s the difference between free chlorine and total chlorine?

Free chlorine is the active chlorine available to sanitise your pool. Total chlorine is free chlorine plus combined chlorine, which is chlorine that has already reacted with sweat, sunscreen, and contaminants.

If total chlorine is higher than free chlorine, the pool is carrying used-up chlorine. That causes the strong “chlorine smell” people notice and signals the pool needs shocking. A strong smell actually means the chlorine is no longer working effectively, not that there is too much of it.

What is calcium hardness?

Calcium hardness measures the dissolved calcium in your water. When it’s too low, the water becomes corrosive, etching pool surfaces and damaging metal fittings. When it’s too high, it causes scale on surfaces and inside equipment, including chlorinator cells, and turns water cloudy.

Calcium levels can be raised with calcium chloride. High calcium can only be lowered by partly draining and refilling with fresh water, so seek practical advice from our store before draining.

What does stabiliser (cyanuric acid) do?

Stabiliser protects chlorine from being broken down by sunlight. In a Perth summer, an unstabilised outdoor pool can lose most of its chlorine in a single sunny day.

Too little stabiliser means your chlorine disappears as fast as you add it. Too much locks the chlorine up, meaning the pool needs much higher chlorine levels to stay clean. Stabiliser does not break down or backwash out easily, so the only way to lower a high reading is to dilute the water with fresh supply.

What order should I balance my pool water in?

1. Alkalinity first. It buffers pH, so fixing pH before alkalinity usually means doing the job twice.
2. pH second. Once alkalinity is in range, pH is far easier to set and hold.
3. Chlorine third. Chlorine works properly once pH is balanced.
4. Calcium and stabiliser last. These change slowly and rarely need attention week to week.

Make one adjustment at a time, let the pump run to mix the chemicals through, then retest before adding anything else.

How often should I test my pool water?

Test at least once a week. In peak swimming season, after heavy use, or following heavy rainfall, test more often. A home test kit is fine for weekly checks of pH and chlorine. For the full picture – including calcium and stabiliser – a professional test gives accurate, reliable numbers.

Get your water tested free in Claremont

Not sure what your numbers mean or how much to add? Bring a water sample into our store at 211 Stirling Highway, Claremont. We will test it free and tell you exactly what your pool needs. Shop pool chemicals and pool test kits online with delivery across Perth and regional WA.