Started with Baquacil because I supposedly saved money


LifeTime Supporter
Oct 17, 2009
New above ground pool. Started with Baquacil, because I supposedly saved money by getting it in a package. After less than a month, the pool store recommended I shock and sanitize it for the third time as the level wouldn't stay above 30 for more than 6 days. I basically said no way as the money for 3 shocks treatments and 3 sanitizer treatments seems ludicrous for 1 month. Also, it's cloudy for 2 to 3 days after adding sanitizer.

I'm on conversion day 3 and I've "over shocked" the pool. Somehow I got FC up around 22 last night even after following the calculator. This morning it was 6 I shocked it this evening at about 6:30 (raining/no sun). I just tested it 2 hours later, and it is at 16.5. I tested again at 9PM and it "increased"????? to 19.5.

So perhaps I'm miscalculating my water volume:
-The pool store said 17,500 gallons
-The installation guy said 18,000 gallons
-Jason's calcuator says 15,700 gallons (seems like a big variance, but look at my overshock results).

So if anyone can help, I have a few questions:
1) What kind of stress am I putting on the pool by overshocking abave 15 FC?
2) Is there a logical reason for the increase in FC?
3) I think I answered my question on the volume, well maybe.


18X33 oval above ground, 54inch walls, 48 inch water height.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Extremely high FC levels can shorten the lifetime of the liner. Usually that means the liner gets faded and brittle a little sooner than it otherwise would, a very long time from now. Since the high FC level only lasted a short time, I wouldn't worry about it too much, but reduce the amount of bleach you are adding next time.

FC could be going too high for quite a few reasons. Bleach can be stronger than it is labeled, the pool could hold less water than you think, you might have had a typo when calculating or have used a jug of bleach of a different size than you thought.

Measure the width, length, and depth of the water (not the outside of the walls) with a tape measure, rather than depending on the "official" size, plug those numbers into the Pool Calculator, and you will be extremely close to the actual amount of water (because your walls are vertical and the depth doesn't vary).


Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
Houston, Texas
Double check your "now" numbers when you use the pool calculator. It doesn't always retain the last numbers you entered.
What are you shocking with?
Which estimation of pool volume are you using?

Do you know how high you are above shock level? I am assuming your pool could handle Mustard algea level which is usually 10ppm higher than regular shock level. A few days of elevated shock level should not hurt.

Next time you do the drop test for chlorine, make sure the drops are all about the same size. If the drops start getting smaller try wiping the dropper tip with a damp cloth.


LifeTime Supporter
Oct 17, 2009
Day 4

Thank you! I'm relieved I haven't damaged anything. My morning FC is a much more reasonable 16.5, so it would seem I'm getting very close to the 15 FC mark. My FC drop is shrinking drastically down to no more than 3!!

We'll see what the pool calls for tonight; My thought is to put in the chlorine in two steps 1 half hour apart and take a measurement between this time around. Thoughts?

Shock - 12.7 liquid chlorine from the pool store 5 gal jug.
Tape measure - used for depth, but not length and width (I will now). I'll go with Jason's calculator for volume this time.
Using measuring cups - as I'm pouring from a large container.

Temp - 65
FC - 16.5
TA - 100
PH - 7.2

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