/diy/ - Do It Yourself

I'm trying to disconnect my washer.

I thought these valves were supposed to be fairly simple. Should it not be a simple 1/4 turn to shut them off? They are giving me resistance, and I'm worried to twist too hard because the pipes are twisting with them if I start to give it some muscle.

Do I need to unscrew that screw at the top of them first to loosen it so I can twist it, or do I just need to put a bit more muscle to twist it into off position? I'm a little paranoid, I dont want to cause leak by twisting too hard and breaking something if they should be unscrewed a bit first.