I have a Pentair 6 port multivalve sand filter, 2 years old. Noted water coming out of waste line last week which corrected after moving valve position. Yesterday I backwashed and after turning valve back to filter, water started pouring out of top of filter where handle is located. I took the top apart and noted the rubber o ring on the stem atop the spring had broken and was stuck in the spring. Took to local pool store who said I would need to replace the entire top portion ($220). My question is, is there an ORing that I could buy in store at home supply store or pool store that would work?