LifeTime Supporter
May 23, 2009
Trenton NJ
Just opened this morning. Had a few inches of water to backwash above skimmer. My Cya was zero, so I added 8 lbs. cya in a stocking in front of return. I have to remember to go back and agitate more often, the cya just sits there in a lump.

Anyway I shocked at 24 ppm around 10:00 am and tested at 4:00 pm and I now have .5 fc

So I went and bought 5 gallons of 12.5% chlorine and dumped that in.

The problem is I should have checked the pump psi first because it's running 10 psi over normal. I don't want to backwash the chlorine I just put in....also some cya.

Should I just leave it til morning? I'm sure I'm gonna need more chlorine. The pool looked bad this year. Must been because we had a mini heat wave last week.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
Backwash anyway. You'll only be losing a couple inches of water. Less than 5% of the total volume, so maybe 1 ppm FC and maybe a little more of the CYA. Hardly enough to notice on a test.

Or switch to recirculate while you are asleep, and backwash and resume filtering tomorrow morning.


Well-known member
Oct 9, 2015
Niagara Falls
Yeah, if the chlorine is fully 'mixed' then back washing won't affect your chlorine level 10ppm in a whole pool is the same proportion as 10ppm in a 10ml sample (in theory, assuming it's circulated). But if you're not sure, recirculate overnight. Just don't forget to backwash BEFORE your next dose.