Great Season, but With Metals Should I Shock to Close?


TFP Expert
LifeTime Supporter
Apr 27, 2012
Grand Rapids, MI
By way of background...
I've had a Great season controlling my iron with metal magic this year.
I am getting ready for a scheduled closing Monday by pool tech (I don't let them touch the chemistry...just the lines and winter cover, equipment closure etc)

I raised my cya a bit by using tabs while on vaca last mo. and then continued in cooler weather since in these parts it dilutes every year anyway..,went from 30 in season to 50 now...figured it wouldn't hurt over winter to keep some ch stabilized in reserve ;) (I usually lose about 15-20 ppm over winter if there's a lot of snow.)

In the past, I've raised to a lower shock level day or so before, let drop, then add polyquat per Jason's reccs.

Ph right now is 7.4....a little higher than I've kept it in years past but that's because the etal magic likes a ph of 7.6 to start as it drives it down a bit.

This time, my shock level would be 20 ... And I do have iron. I'm curious as to whether I run a higher risk of oxidizing the iron and staining at 20. I have an extra bottle of Metal Magic I can add to offset.

Or in my shoes, would you drop the ph by a few points before shocking? Or, since I have borates and am adding polyquat, would you skip shock level and just bring it up to 12-15 or so.

Each of three years prior, I open to about 3 ppm of FC left each spring at those levels.

Thanks in advance for any input!


TFP Guide
In The Industry
May 14, 2007
New Brunswick Canada
If you can pass oclt, why the need for shock, you are tempting those metals out with the Ph rising due to SLAM. IMO Polyquat should suffice if you passed OCLT.

Do you know if your rain water is acidic? That could help keep it down in the winter. It works on my pool.

My area has TONS of metals in water, so much so, that installers lean towards grey skimmer, drains, returns, steps LOL