As an owner of a hot tub you may at times find that your hot tub heater element is not working properly. Tub water which is not heating at all, or is not heating enough, are two almost-sure signs you have a heater element problem. To be sure the tub's heating element is bad, you'll need to check the element.
With one terminal of a multimeter touching one of the element's terminals, touch the other terminal to a ground. Now, check your meter. It should read 240 volts if the element is getting power. If it is getting power, check the element's relay, or switch, with your multimeter.