How Low Alkalinity Creates Corrosive Water

Total alkalinity acts as a buffer for your pool's pH, preventing dramatic swings that can wreak havoc on equipment. When alkalinity drops below the recommended range of 80-120 ppm, several problems compound:

• pH becomes unstable: Without adequate alkalinity buffering, pH can fluctuate wildly—a condition pool professionals call "pH bounce"
• Water becomes aggressive: Low alkalinity combined with low pH creates corrosive, acidic water that actively seeks minerals from any available source
• Equipment suffers: This hungry water attacks metal components throughout your pool system, including pumps, heaters, and crucially—your ioniser electrodes

For copper ioniser owners, this creates a perfect storm. Your ioniser electrodes become an easy target for corrosive water, dissolving copper into the pool far faster than intended.

Effects on Your Copper Ioniser and Pool

Accelerated Electrode Corrosion

Copper ionisers work by slowly releasing copper ions through a controlled electrical process. Under normal conditions with balanced water chemistry, electrodes typically last one to three seasons before needing replacement.

When water becomes corrosive due to low alkalinity:

• Electrodes dissolve at an accelerated rate, shortening their lifespan dramatically
• Copper releases into the water uncontrollably, bypassing the ioniser's regulated output
• You'll notice electrodes appearing pitted, eroded, or bluish-green earlier than expected
• Replacement costs increase significantly as you burn through electrodes faster

Pool Surface Staining

Once excessive copper enters your pool water, the problems multiply. Dissolved copper can oxidise and precipitate out of solution, leaving behind distinctive staining:

• Green or blue-green stains: The classic copper stain appears on pool surfaces, particularly noticeable on light-coloured plaster, pebblecrete, or fibreglass
• Black staining: In some cases, copper deposits can appear black, especially when combined with other minerals
• Difficult removal: Unlike organic stains, metal stains bond to surfaces and require specialised treatment with metal sequestrants or acidic solutions

The frustrating part? Once staining occurs, simply balancing your water won't reverse the damage. You'll need targeted stain removal treatment.

Green Hair—Yes, It's Real

Perhaps the most alarming effect of excess copper hits close to home—literally. When copper levels climb too high, swimmers can emerge from the pool with a greenish tint to their hair, particularly noticeable in blonde, grey, or light-coloured hair.

Here's the science: copper ions bind to the proteins (keratin) in hair strands. When chlorine oxidises this copper, it produces that distinctive green hue—similar to how the Statue of Liberty developed its famous patina over time.

Research has shown that damaged or chemically-treated hair is particularly susceptible, as the broken bonds in bleached or straightened hair make it easier for copper to attach. While the discolouration isn't permanent, it requires chelating shampoos or home remedies like baking soda paste to remove.

Reduced Sanitisation Effectiveness

Copper ionisers are designed to work within specific water chemistry parameters. When pH and alkalinity fall outside ideal ranges:

• The ioniser may not function effectively, failing to release adequate copper ions for algae control
• Any chlorine you're using alongside the ioniser becomes less effective at lower pH levels
• Bacteria and algae can gain a foothold despite having an ioniser running

It's worth noting that copper ionisers have inherent limitations—they don't kill fecal bacteria and work slowly against some pathogens. When water chemistry is out of balance, these limitations become more pronounced, potentially compromising pool safety.

The Ideal Water Chemistry for Copper Ioniser Pools

To protect your investment and keep your pool safe, maintain these parameters:

Ioniser manufacturers specifically recommend keeping pH between 7.2-7.4 with alkalinity between 90-120 ppm. At these levels, your water can safely hold up to 0.5 ppm copper without staining risk.

Prevention: Your Action Plan

Test Weekly

Regular testing is non-negotiable with ionised pools. Test your alkalinity, pH, and copper levels weekly using quality test strips or a liquid test kit. Don't skip copper testing—it's the only way to catch rising levels before staining occurs.

Raise Low Alkalinity Properly

If alkalinity drops below 80 ppm, increase it using sodium bicarbonate (available as "alkalinity increaser" from pool shops). Add it gradually—about 1.5kg per 10,000 litres raises alkalinity by approximately 10 ppm. Wait for full circulation before retesting.

Use a Metal Sequestrant

Consider adding a quality metal sequestrant to your maintenance routine. These products bind to metal ions in the water, preventing them from oxidising and staining surfaces. For ionised pools with light-coloured surfaces, use a chelating agent at least twice yearly.

Note: Some sequestrants contain phosphates, which can feed algae. Check with your ioniser manufacturer for compatible products.

Monitor Electrode Condition

Inspect your ioniser electrodes monthly. Signs of excessive wear include heavy pitting, significant colour change, or visible erosion. If electrodes are wearing faster than expected, investigate your water chemistry—it's often the culprit.

Address Staining Quickly

If you notice early signs of copper staining, act immediately. Balance your water chemistry first, then use a metal stain remover. The longer stains set, the harder they become to remove.

When to Seek Professional Help

Bring your water sample to a professional pool shop if you're experiencing:

• Persistent green or blue-green water despite balanced chemistry
• Rapid electrode wear (needing replacement more than once per season)
• Stubborn staining that won't respond to treatment
• Difficulty maintaining stable pH despite adjustments

A comprehensive water analysis can identify underlying issues that home testing might miss, including total dissolved solids and other factors affecting your ioniser's performance.