Yeah, they create some back pressure on the pump that will vent out the release valve. It will dump a fair amount of water so you want to put it somewhere that can handle it or you'll end up with a lot of standing water. It can be a pain to find a good spot to drain it to but it is less of a pain than replacing a well pump. The CSV is about $100 +/-, depending on the size and pressure. If that well pump is cycling from 45PSI - 75PSI, I'd get a 60PSI CSV and nozzle my heads to take full advantage of that.