Tenant switched off hot water - other tenants complaining

[Alex Reamon]

I own a four unit dwelling in New Jersey.  One of the units (ground-floor) includes the basement in its living space. De facto this also includes the utility room, which is a separate room in the basement (the door does not lock).  Due to the floods, the water heaters' pilot lights went out and I had to send a repairman over to relight.  

However, the ground-floor tenant has been doing some reading and has come to the conclusion that he doesn't feel safe having his family right above this equipment, so he turned off all the water heaters.  He's asking that they either be replaced entirely or that the controls be replaced.  My insurance should cover this, but in the meantime the whole building doesn't have hot water.  I told him he doesn't have the right to make that decision and to turn the units back on, but he's not listening.

Any advice on how to handle this?