We replaced our 32 year old hot water heater today. We turned off the main water supply to the house during the process. Installation went great. However, when we turned the main water supply back on, our kitchen faucet started blowing a mixture of air and water (very forcefully), then it wouldn't do anything, and now we can only get a steady trickle out of it. The in-fridge water dispenser is not working at all, but the dishwasher is working fine. All three are on the same wall. We have tried closing and reopening the kitchen valve under the sink and purging the main water line (by purging, I mean turning main supply off, then turning on 2 faucets that were working fine, then turning the main supply back on). So far, no changes. Every other faucet, shower, and toilet works perfectly. The problem seems to be isolated to the kitchen faucet and fridge line. Anybody have any idea?

Remove the kitchen faucet aerator and test for volume and pressure. Clean or replace the aerator. If you do not get pressure and volume with aerator removed you will probably have to dissemble kitchen faucet and clean it.

Most likely the dip tube in the old water heater had deteriorated and crumbled. When you pressurized the new water heater, the air pushed all crumbled dip tube material that was in the pipes, to the faucet.

May have to do the same for the line to fridge.