Had Lennox Tech come out to service my 1994 Lennox Pulse. Still working like a charm. He saw my marker dates where I had replaced my flapper every 4 years. He asked me if I replaced it or just cleaned it off. I told him I replaced it. He said that was unnecessary as all I had to to was wipe it clean. Yes, I know he is a Lennox Tech and he loves the old Pulses. But, is it really ok to wipe the flapper clean? I thought it was some kind of filter???