Electronic oxidation reduction potential (ORP) and pH meters can provide precise numeric measurements. Still, these devices are subject to their own types of errors.

“They’re good instruments,” says Richard LaMotte, vice president of sales and marketing at LaMotte Company in Chestertown, Md., “but they have some interferences that people need to be aware of.”

These interferences usually take the form of chemical accumulations on the metal electrodes. “A lot of times, [homeowners] don’t maintain their system’s controllers, so we don’t get accurate readings from them,” says David Coonan, operations manager at All American Pools and Spas in Norwalk, Conn., a Pool & Spa News Top Builder.

These errors can often be avoided by keeping the electrodes clean. Experts agree that it’s also important to calibrate ORP and pH meters at least once every few weeks.

“If you get a really low reading, you know you’ve got an issue there,” LaMotte says. He also points out that a test strip or titration kit can help verify whether the meter is malfunctioning, or if there’s a genuine chemistry problem with the pool. Thus, even in this age of electronic technology, it’s still important to keep some trustworthy standby kits handy.