PJay... You said, "I took the old one apart and found the rubber bits dirty and covered with a thin furry looking stuff."
Did you determine what the "furry looking stuff" was?
Was it something growing?
Most of us use chlorine bleach (clorox) NaOCL, sodium Hypochlorite... to sterlize our fresh water holding tank.
Chlorine is aggressive... when very strong it isn't good for rubber or neophrene parts, or even metal parts like screws and clamps.
When people have arobic or anarobic algae growing in their fresh water tank they tend to put to much "chlorine" in the tank. ( 1/4th of a cup is pushing it)... but do treat your tank at least a couple of times per season then empty after a few hours and rinse with freah water (baling soda is ok in the rinse... but flush it too.)
This is especially important when you are filling your water tank from many sources over time.
Too much of a good thing is as bad as nothing at all.