Installed customer supplied 50 gallon short electric water heater with new pan and isolation valves. Once the new heater was installed I noticed that I did not have 240 volts at each leg like did yesterday. Traced the issue back to the existing 30 amp double pole breaker that kept tripping inside the panel. Ended up installing a new 30 amp double pole breaker inside the panel, water heater is now getting 240 volts with no issues. Did not charge any extra for installing the breaker, but did charge for material. Emailed copy of invoice to homeowners email.