How to Measure Magnesium Hardness in a Swimming Pool

Magnesium hardness is a measure of the amount of magnesium dissolved in your swimming pool water. It contributes to the overall water hardness: Calcium hardness plus magnesium hardness equals the total hardness of the water. If the levels become too high, it may cause a scaling on the handrails, ladders and deposits in your pool.

Difficulty: Moderately Easy

Instructions

1. Purchase a swimming pool water test kit to check your water levels for hardness. A basic test kit will check free chlorine, total chlorine, pH and alkalinity. Or take a sample of your pool water to your local pool dealer for testing.

2. Fill the test tube to the indicated line with pool water. Make sure you obtain your sample at least 18 inches below the water's surface, and stay away from the pump inlets.

3. Seal the test tube and shake it.

4. Determine the level of magnesium hardness in your pool water by matching the test colors to the shade on the test tube.

5. Speak with your pool representative to determine which chemicals you must add to your pool water to stabilize the magnesium level and control magnesium hardness.

Tips & Warnings

• Put all water samples in a glass or plastic jar or container.
• When you shake your test tube, do not use your hand or finger to cover it. Oils from your skin will contaminate the sample.