Problem using a Relay and electrovalve

Hi everyone!

Im in a project using arduino to control a electrovalve. The project is simple, arduino dettects and interruption from a button and activate a relay so that the electrovalve switches on and the water flows for a certain time and then it switches off and stops the flow of water.

Everything works fine when it is unplugged from electrovalve. When plugging to electrovalve arduino does what I expect but the relay keeps restarting, as soon as I plug mains relay activates itself during 15 secs and deactivates but instantly it switches on. If Restart the arduino everything becomes fine once again but as soon as I reactivates the arduino gets crazy once again.

Does any of you guys can help me?

(Im not english speaker so apologize if wrong language)

Circuito.png