Water's pH level refers to how acidic, neutral or alkaline it is. Determining pH is important for persons raising fish who require a specific pH level or for gardeners who want to make sure that the soil remains viable by not using a very acidic water. The pH level can be measured with a probe and meter or with litmus paper.

Measure Your Water's pH Level

Before trying to lower your water's pH level, you should first take a sample from your water source and measure its pH level with either litmus paper or a probe and meter. A probe and meter is the most accurate method of testing pH level, but it requires expensive equipment. Litmus paper is typically a good, cheap alternative and will at least give you a general estimate of your water's pH level. Choose a method that suits why you want to lower your water's pH level; if you need the level at a specific point, then it is recommended that you invest in a probe and meter. Whichever method you choose, test a sample of your water and write down the pH level.

Lowering the pH Level

Typically, you use acids to lower the pH level in your water. Hydrochloric acid (also known as muriatic acid) lowers pH levels in water. You can purchase muriatic acid at most hardware stores; it is typically used to clean bricks. Keep in mind: hydrochloric acid is a dangerous substance. It can cause coughing or inflammation if inhaled and severe burns on the skin if spilled; exercise extreme caution when using this substance. In extreme circumstances, exposure to hydrochloric acid could be deadly.

Use the following method to lower the pH level of small quantities of water to be used for your garden or your fish tank; lowering the pH of your general water supply would entail much effort and is beyond the scope of this article. To lower the pH level in your water effectively, you need to add enough acid to eliminate the water's "buffering capacity." The buffering capacity refers to the water's ability (based on the make-up of the water) to remain at a stable pH level. The level will vary based on the minerals, nutrients and other substances in the water. Once the buffering capacity has been nullified, the pH level in water can be easily tampered with; adding more acid will lower it.

Understand that water with a higher pH means that it has a higher acidity. Adding acid to water, therefore, reduces the buffering capacity of the water and, eventually, reduces the water's pH level.

Vinegar is an acetic acid. If you do not have hydrochloric acid to add to the water, you could try and use vinegar. The problem with using household vinegar is that the solution is only about 5 percent acid. This means it may take much more vinegar to accomplish the desired result.