Dear Gilda: Please turn the unit off now! A very, very dangerous situation exists. The unit has an earth/ground fault on the element or control system, possibly in the flow solenoid. Also, if you are getting shocked, the stray earth/ground leakage voltage/current is passing through your client and not the ground wire. You have a bad or missing ground connection between the unit & the breaker panel and/or ground rod. These units in Cuba are controlled the same way we do it back in England: with a double pole ceiling mounted pull-switch. The switches are available, but it won't stop your client getting shocked! Honestly. I'm not there, so I can't troubleshoot it for you. But if it's leaking & shocking, it needs replaced or repaired very soon. What brand unit is it? and what is the voltage & wattage rating on it? I have access to these units, also undersink instant type water heaters. If I can help, please call me at 1 800 851 9891 or 318 433 5480. Good luck & be safe, Brian Wood.