I recently had a new water heater installed, shortly after I have had a horrible sewer smell coming from the laundry room which sits directly above the room my hot water tank is located. Could this possibly have any relationship?

Have you used your washer since the work was done? Pour a quart of water in the drain pipe of the washer and answer back if the smell is still there. That water in the 'trap' (the elbow at the bottom) prevents sewer gasses from escaping back into the house. Same with kitchens and bathrooms. If it's not that, it could be a blocked vent (out to the roof) which will require someone to clean it.

Is this an electric or propane or natural gas heater?