I am not sure if they work or not have to wait for a rain. Installed in winter in Wisconsin. This is a huge investment for a homeowner. Our salesperson oversold the product. He guaranteed we would not see the ice damning problems we had. It was his closing deal and a lie. The company did not back the customer that was blatantly lied to. I am in business and if a sales person lied about the expectation of the product we would in a heartbeat make it right. We were not asking for a refund but a discount on a very large investment. Beware of a company that has salespeople that would lie and do anything to get a sale. Worse a company that stands by the lie and does absoluetly nothing about it!