Potassium is an essential element in humans. It is not commonly found in drinking water at levels that could be a concern to human health. However, the consumption of drinking water treated by water softeners using potassium chloride may significantly increase exposure to potassium. This is not a concern for the general population. However, increased exposure to potassium could result in significant health effects in people with kidney disease or other conditions, such as heart disease, coronary artery disease, hypertension, diabetes, and who are taking medication that interfere with normal body potassium handling.
However, potassium levels in drinking water from water softeners using potassium chloride can be very high, and may significantly increase an individual’s intake of potassium that could cause hyperkalemia in susceptible individuals. As a consequence, people with certain medical conditions (and medications) that potentially cause hyperkalemia should avoid the consumption of water (for drinking or cooking) from water softeners using potassium chloride.
Is it regulated?
Potassium if not regulated by the EPA, nor are there World Health Organization WHO guidelines as it poses not real health risk to the general population.
How is it tested?
Laboratories analyzing drinking water samples can utilize various methods including EPA method 200.7 and 200.8 which utilize an Inductively Coupled Plasma (ICP) or the Standards Method 31138 which uses Graphite Furnace.
If the potassium level in the water due to the use of an ion exchange using potassium chloride you may need to switch to sodium chloride to reduce your exposure if you are at risk due to medical conditions. You can remove some potassium with distillation and reverse osmosis.