This is probably a dumb question, but...I am installing a disconnect on the water heater to turn it off when I am gone, which is about ALL the time. I thought I knew what I needed, a 30 amp switch. Sounds simple enough. The problem is this, I found a website that has 2 different 30A indoor switches. One is a 2 pole 3 wire and the other is single pole, 2 wire. Both with solid neutrals. The single pole, 2 wire is only 19.99 and the other is 31.99. They both say they are for water heaters. So which do I need???

Could someone also explain the difference? I am sure once its explained to me it will make sense, but right now its driving me insane! Thanks!!!