Keep shocking. How old is the filter sand? It does wear out after a few
years, Mine lasts about 3 years.....
"Don Phillipson" wrote in message
...
We have not seen in 10 years' use the (above-ground)
pool water so green rather than clear/blue -- and this is
the first time the advice of Sam the Expert at the pool
store has not worked. (This was to shock afresh i.e.
raise chlorine level to 10 p.p.m. from the usual 1 or 2 p.p.m.)

Problem appears to be that the green coloration (dead
algae?) is so fine the sand filter does not retain it.
Backwashing produces a small amount of colour;
but the green never leaves the pool; every morning
the green has fallen to the bottom, so is picked up
by the cleaner, and presumably goes straight through
the sand filter and back into the pool.

Advice?

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)