I have an electric low-boy 40 gal hot water heater that I installed in 1999. This was a rental property that I now live in and I never got a complaint about this problem from any of the renters. The water heater is not leaking and is functioning properly with the following exception. After I do a (full) load of laundry I get a second or two of air when using any of the hot water taps.
This only occurs after the first use of a tap (kitchen faucet, bath faucet, or tub faucet that is all the faucets in the house, one each.) At no time do I get air from the cold water faucets.
At first I thought that I may have hooked up the water pipes wrong (cold line to hot outlet and hot line to cold outlet) but I checked them and they are correct. For the life of me I can not figure out how using the washing machine can be causing air to get into the hot water lines. I usually only wash laundry once a week and after the air is bleed out with the first use I have no problems until I use the washing machine again.
The real interesting part is I lived across the street in a house that is the same size and floor plan as this house and replaced the hot water heater there at the same time as I replaced this one and never had a problem like this over at that house.
BTW water supply is from city service, not well service and these houses are all electric, no gas. Have you run into this before?