I used an electric sending unit on my 12 gallon polyethelene gas tank. The problem I had was with the screws going into the tank, There is no way to get the screws to tighten down tight enough to stop gas from leaking from around the top of the tank. I tried several sealants including Gorilla glue and nothing would stick to the tank. I replaced the tank and gave up the idea of a sending unit on that type of tank.