Cl level sanity check please


New member
Jul 27, 2010
We have a 17,000 liter above ground vinyl lined pool, located inside of a 'green house' to keep the bugs off us.

This year I switched to Borax, 12% liquid Cl, and muriatic acid.

Came back from a 5 day trip to a green pool. Took a sample into the local Surfside pool place to double check the ph level as I have had problems before with high Cl levels affecting the ph test, and they advised me I needed to add 20 liters ( yes, that is 20 not 2.0 ) of the 12% liquid Cl to go from 3ppm to 10ppm. And that liquid Cl was not as good as Dazzle Ultra Shock.

This sounded absolutely nuts to me. The pool calculator indicates the free Cl would be about 150 ppm if I did that.

Took another sample into the Dolphin pool store and the only number the 2 places agreed on was the ph of 7.6.

Both places indicated that Borax shouldn't be used..... And that I needed to quickly get my Ca from 130 or 150 (depending on which test you believe) up to 200. In a vinyl pool?

I should know better that to go into these places!

Anybody else get advice like this?


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Welcome to TFP!

It happens all the time. Hang around and read stories from people who have just discovered TFP and you will hear the strangest things that pool clerks tell people. One of my favorites was telling someone to add 12 lbs of PH Down and 10 lbs of PH Up (which does more or less nothing other than pay the pool store money).


LifeTime Supporter
Nov 18, 2009
Sacramento, CA
It sounds like you already know the answer.

I get 3.5 liters for 7ppm increase. Dazzle Ultra Shock (whatever that is) is not "better" than liquid chlorine, and may be worse depending on what is is and what your numbers are.

Borax is fine to raise pH, which you don't need to do.

Your CH is fine. Low CH is irrelevant to vinyl pools (High CH is bad for any pool).


LifeTime Supporter
Jun 17, 2010
Glendale, CA
Buying a TF-100 test kit was the single biggest money saving move I've made this year. It'll free you from all that pool store madness and just put you in the drivers seat.

You can bet the green is due to low FC levels. When you say "high" what is that? Our pool store was telling us 3ppm was too high - with CYA of 150. Our pool turned a lovely shade of emerald :evil:

No one is going to acknowledge Borax. No manufacturer specifies borax for use in pools and regulations (for anything really) get written such that products cannot be used in ways unspecified by the manufacturer. The only regs that exist are for public pools, We live in a litigious society .... what's a pool store to do?

They do have several products in the store that are chemically similar though, as in they contain borates. I doubt they'd tell you not to use those. :wink:

As for shocking at 150ppm FC... It'll kill the algae. :shock:

Clearly you already know you're getting bad advice.


LifeTime Supporter
Jan 11, 2009
Cupertino, CA
You'll see borates suggested sometimes for spas, but I doubt any commercial joint would suggest it for a pool. Although I believe one or two of the freelance service guys who hang around here will do it.
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