My I want to install one of the items on my water heater but here in mexico for the 220V heaters is use 2 hot lines lines (110V each) any way to use one of your items?
Sonoff won't handle the amperage required by a water heater. You could place a 2 pole HVAC contactor rated for continuous duty with contacts rated equal to or greater than your heater's circuit breaker current in a proper enclosure and use Sonoff to control the coil. A possible circuit is below. As always, consult a qualified electrician and use at your own risk.