you should cut the ground in m opinion... which ground i am not totally sure... i got a helms in my garage and i will look it up tomorow when i get a chance... anyway it is the ground you should cut... if you cut the power it will work to (it will stop the power to the pump) but you are also taking a chance at damaging your pump... maybe if you put a relay or fuse box then you would be safe.. but i am not sure... i will check and find out for you... also you might want to post in the security section they might be able to help you too... but i will try and see if i got something... good luck