I installed a dedicated vacuum line with a vac-lock fitting like this when I built our inground pool. I've got a basic vacuum head with a 1 1/2" vacuum hose. The hose fits fine into my skimmer, but it's too big for the vac-lock fitting. The vac-lock is 1 1/2" I.D. and the O.D of the hose is 1 3/4. Is there some kind of adapter I can get?