Hydrochloric acid is a builder that can be found in household cleaning products. We use it to make a product formula clean better by affecting the molecules in the formula so they work together better. Hydrochloric acid can also be used as a pH adjuster that alters the pH of a product. Every formula has an optimum pH to make it work best. For example, a formula that is more acidic works better for soap scum removal. Its opposite, a formula that is more alkaline, might be more effective as a carpet cleaner. We use pH adjusters to make sure we achieve the best pH for a particular job. We also sometimes use hydrochloric acid as a cleaning agent that removes hard water deposits.