OLD SCI-FI MOVIE ABOUT HUMANOID ROBOTS INVASION - WATER WEAKNESS

Hi, I'm looking for an old horror/sci-fi movie I saw as a child. 

It was about human-like robots which took control over some US (I guess) small town. 

There was a scene on the stadium where main character realized that "humans" around him aren't really humans and that their weakness is water. 

He sprayed them with firehose and they were getting convulsions. 

I hope it will be enough for someone, cause that's all I can remember. I was very little. 

Thanks