if algaecide consumes FC why add it at closing?

[pookiesunshine]

From post 2 in this thread Low Chlorine after algaecide
note suggests that algaecide consumes free chlorine. if so, adding it at winter closing seems counter productive.
does anyone have any info on what kind(s) of algaecide consume FC? or dont?
eg, polyquat 60; pool tech (Quaternary ammonium compounds, benzyl-C12-18-alkyldimethyl, chlorides )

Seems like i've read somewhere that ammonia will consume FC and wondering if the pool tech would.

Thanks,

 

[pooldv]

It doesn't consume that much FC and FC consumption is very low when the water is below 50°f anyway. It is really just used as some insurance. Most things added to water will consume some FC, especially organic things. Ammonia consumes very large amounts of chlorine.

 

[JohnT]

Not really that big a deal because your chlorine isn't going to last all winter anyway. I've never really seen the benefit of raising the chlorine level before closing for that very reason. My pool is clean and properly chlorinated so I add algaecide (if I have it) and close. Pool is generally cleaner in the spring with the polyquat.