Ive got a Kohler Deckmount tub faucet with a built in diverter for a handheld. It's been in the house since it was built in 2007 and has worked fine. We turned the house into a rental 6 months ago, and the tenant called tonight to tell me that if he turns on the hot water handle, he gets cold water. It had been working fine for him previously. There's no issue with getting hot water in the shower or the sinks in that bathroom- just at the tub. Could it be a bad cartridge? I can't understand how cold water is getting to the hot water handle/valve at all- wouldn't the cold water valve have to be open for that to happen?