4 Reasons Pool Water Looks Green But Clear & Best Ways to Fix

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Why Does My Pool Water Look Green But Clear?

When pool water looks green but clear, one or more of the following may be going on:

Chlorine Levels are Too High, pH is down and corrosion is taking place
You have used Copper based Algaecides
Copper Compounds in Your Pool Water
Initial Stage of Algae Growth, algae is not floating in the water but just sticking to the pool walls & floor

I must admit that the scenario of “pool water looks green but clear” is not the most common one for green pools, but it can happen. Generally, when pools go green, the water gets cloudy too. This scenario is the most common one and it is possible to clear such green pools by shocking it.

However, when pool water looks green but clear, you need to test the pool water for several parameters and arrive at the course of action to be taken based on the test results.It helps to know some pool water chemistry!

Testing When Pool Water Looks Green But Clear

So, of course, before you can start turning your pool water that looks green but clear to a crystal clear blue color, you will need to test the pool water and determine the actual reason.

Typically, there are three test options available:

Test Strips
Chemical Test Kits
Electronic Test Kits

Most home pool owners use test strips and some may use chemical test kits. The trouble is that these do not measure metal levels in the pool.

Of course, you do not have to invest in some high priced, fancy, water testing equipment. Your friendly pool chemicals supplier can do it for you.

So let me explain each specific reason and the best fix for it!

Reason #1: Chlorine Level Too High

It might seem counterintuitive, but having too much chlorine in your pool can lead to a greenish tint. This paradox arises because high chlorine levels in pool water reduces pH and makes it acidic & corrosive.

Pool water typically has a certain level of metals, in the form of soluble compounds. Moreover, some of the pool equipment and accessories, such as filters, pumps, vacuums and ladders, are also metallic.

Extremely high levels of chlorine can cause the metals in the pool water to oxidize. The soluble metal oxides may give a greenish hue to the pool water.

To prevent this issue, regularly test and maintain your chlorine levels within the recommended range. If chlorine levels are high, gradually reduce them to prevent unwanted water discoloration.

Reason #2: Use of Copper Based Algaecides

Algaecides are chemicals specifically designed to prevent and control algae growth in swimming pools.

However, when pool water looks green but clear, it is an indication that you are using copper based algaecide. Moreover, it is also possible that you are using higher than recommended dose.

Even when the chlorine levels in your pool are within the recommended range, it will react with the copper in the algaecide, form cuprous chloride which makes the pool water look green without making it look cloudy.

To get your pool back to a crystal clear blue color you must switch from your current algaecide to one that is metal free.

ProTeam Polyquat 60 is an algae preventative for hard-to-kill mustard, black, and blue-green algae types. This product is non-metallic and non-staining. It also reduces sanitizer consumption and is not affected by high chlorine residuals.

Reason #3: Copper Compounds in Your Pool Water

Even when chlorine levels in your pool are within recommended levels, chlorine will still react with copper compounds in your pool water to form cupric chloride. The result is that your pool water looks green but clear.

There are many ways in which soluble metallic compounds, especially copper compounds, can get into your swimming pool. Here are some of them:

1. Water Supply: Metals occur naturally in well water and many municipal water sources, which supply your pool with water.

2. Rainwater & Storms: Rainwater also contains certain metals which can be deposited into your pool during a storm. Flooding can cause mud, mulch and other debris to enter your pool.

3. Pool Chemicals and Equipment: Many pool chemicals, equipment, and structural components of your pool have metal components. If your water is unbalanced and corrosive, this can cause metals to enter the water.

4. Pool Heater: The copper heat exchanger can break down due to a poor chemical balance, causing the metal to enter the swimming pool water.

5. Accidental Introduction: Metals can accidentally find their way into the pool; hair clips or non-pool toys are common sources.

6. Fertilizers: Many lawn and garden fertilizers can contain high levels of iron, copper, manganese and other heavy metals.

Regular testing and adjustment of pool water chemistry can help prevent the build up of metals in your pool. Sequestering agents are effective in combating the problem.

Pool Mate Metal Out is especially formulated to help prevent discoloration of pool water due to iron, calcium, magnesium, copper and other minerals and metals.

This product is particularly ideal for pools using well water or in regions where heavy metals are naturally present in the water. Pool Mate Metal Out is ideal for controlling general stains and helps maintain a sparkling clean pool.

Reason #4: Initial Stage of Algae Growth

In case your pool is not adequately sanitized (that is, free chlorine levels have been low) algae, especially green algae, may start to grow in your pool. In the initial stages, algae are tiny and cling to the pool walls and floor.

At this stage your pool water looks green but clear, because the algae is not yet floating in the water. Think of this as a wake up call!

If pool water test results show that free chlorine levels are low and/or combined chlorine levels are high, your pool needs the “shock” treatment. Shocking the pool is the same as super chlorinating the pool.

Free chlorine level is spiked 10X, overnight to eliminate combined chlorine build up and destroy the early signs of algae growth. Once the algae have been annhilated and the chlorine levels are back to normal, you need to get rid of the dead algae.