My hot water pipes were frozen. At first only the washer had hot water. Pipes began to unthaw on half the house. Hot water worked fine. When the other half started to flow ALL water running is cold. Checked water heater and it is lit. What could be the problem?

Hi SleeplessinChi

Ouch! My first guess is that there is a MIXING VALVE (could be any faucet/valve with a single handle , including single lever washing machine valves, as an example) that got damaged as a result of freezing. If you had hot water at the beginning of the thaw, I don't think the issue is a broken DIP TUBE (can google this), so there is some work to do, for sure!!

Something like this can be tough to pin down because we can't usually isolate the tub or tub/shower valve(s) in the home. Tell me what fixtures are in your home and we'll tell you if you need to pull a plumber in, OK?

Mark