The instruments used in every water treatment plant fall into two broad categories: laboratory instruments and process monitoring and/or control instruments. Basic laboratory instruments that nearly every water treatment plant should consider are discussed, including: turbidimeters; pH meters; jar test apparatus; colorimeters; online process‐control instruments; microscopes; and balances. The selection process should consider location, intended use, availability of prepackaged reagents, required degree of precision and accuracy, accessories, and an economical method of analysis in compliance with regulatory agencies.