Water Chemistry 101 – Metals (Copper & Iron)

You may be asking why would Copper and Iron be in your swimming pool water?

Great question. After all, it does seem a little strange that metal is in your pool water.

However, there is a reasonable explanation. But, before we answer the ‘why’ question let’s first answer the ‘what’.

If you’d like to jump ahead feel free:


What are the problems with copper and iron in pool water?

If you’ve ever travelled Europe and gone to one of those stunning fountains in the middle of the streets of Paris or Florence, then you would have inevitably looked down. What you find under the water lining the bottom are sometimes thousands of coins dating back sometimes hundreds of years. Now, have you ever noticed the colour of some of the coins?

You can always tell the new coins by their shiny usually silver surface the old coins however are often a little green. This green is caused by oxidation in the water reacting with the copper in the coin. Pool water is no different. Small particles of copper can turn the pool water a tint of green.

Now iron, on the other hand, has an entirely different reaction. You continued looking at the bottom of the fountain and noticed something a little different. You go to investigate and realise it is a bobby pin that has fallen out of someone’s hair as they were leaning over staring at all the coins. The bobby pin is rusting a brown colour. Small iron particles in pool water can tint it the colour brown.

Sufficient quantities of Copper and iron may be present in the swimming pool water that they cause problems of discoloration. Even a perfectly balanced swimming pool water can have metal problems.

So, copper and iron can colour the water (without making it cloudy) and can cause ugly stains in your swimming pool surfaces. Correct! At its worst, high levels of copper can even stain hair and nails.


How does copper and iron get in pool water?

There are multiple ways copper and iron can enter your pool water below in ranking order are the most common.

1: The use of Algaecides

Algaecides are the preferred method to control algae growth effectively, but some of the most effective ones are copper-based. Algae is killed when it ingest algaecide containing copper-based molecules.

2: Your water source

Your local water source can supply enough metal that over time it can build up to become a problem. Copper, iron and other metals and minerals are naturally found in your water source.

The local water supplier usually only filters enough metals and minerals to keep levels to acceptable drinking water standards. Their primary concern is your health, not the health of your pool and each time you add water to your pool, a little more metal is added.

3: Low pH level

A low pH level can cause metal pool surfaces and piping (mainly in older pools) or metal heat exchangers in pool heaters to corrode and break down allowing the metal to enter the water.

For this to occur it depends on factors such as how low your pH is (the lower the pH the more acidic in nature your water is), how long your pool has had the low pH, and how much metal is exposed to the pool water.

4: Improperly-sized pool equipment and plumbing

If the equipment is incorrectly sized then, water can run at higher pressures than recommended. If your pump is too powerful or the pipes and fittings are too small, aside from causing strain on the equipment it can wear the metal surfaces.

The surfaces might still appear fine when looking at them, but under a microscope, you would see small wear spots on the surface. Over time, small amounts of metal have been released and dissolved in the pool water.

5: Using a water ioniser

If you use a copper/silver ioniser in addition to chlorine to sanitise the pool, then chances are your increasing the metal levels. An ioniser adds copper and silver to the pool water in the course of their normal operation.

These devices shouldn’t cause a problem if you keep your pool water balanced all the time. Imbalanced pool water can degrade these devices, shortening the cartridge lifespan and adding metals into your water.


How to test for copper and iron in pool water?

Aside from a visual diagnosis, and even this can be difficult to an untrained eye, the best way to see if your water has a high level of metal is for us to complete one of our state-of-the-art electronic water test.

This test will let you know what metals are in the water and at what quantity so you can make an informed decision on how to treat it.


How to remove copper and iron in pool water?

To solve the problem there are two general approaches:

Drain the pool. Although not the preferred method it sure is effective. If looking for the cause of the problem, after eliminating algaecides and checking your equipment it could be the local water source. Before dropping the water level have the water source tested first.

Use a chelating agent such as IQ Metal Magnet. IQ Metal Magnet forms a bond with the metal ion and prevents it from being oxidised by the chlorine. Follow this with IQ Pool Shimmer, which binds the metals in the water so that the filter can pick it up. Then backwash or clean the filter and job done.


How to prevent copper and iron in pool water?

If the source of the copper or iron cannot be found or if it cannot be avoided, regular use of a chelating agent such as IQ Metal Magnet will ensure that any new metals in the water will be prevented from oxidising.