Chlorine spiked >300% than it should have

[Elkie108]

Hello!

Today I added 6.8oz of Cal-Hypo 73%. Using poolmath to calculate that should have raised my FC 3ppm. Instead it raised about 10ppm. I'm not terribly concerned about the FC level, just curious as to ideas why? Would like to make sure I'm not missing anything. Attached are my logs from the past couple days.

A little background... I did SLAM my pool which ended earlier in the week. Also, I've had a 0 CYA until I added the liquid stabilizer yesterday and now I am at 40ppm.

Lastly, I'm aware certain tests don't test to decimals but I like to know if its a solid number or perhaps it hovered slightly downward.

TIA... super appreciate everyone's help!

 

[mknauss]

Not sure why it jumped your FC up so much. Typically testing error on either the before or after test. I am curious, how did you measure out 6.8 oz of cal hypo??

 

[Elkie108]

I use a kitchen scale (I'm a baker and pretty familiar with measurements). I tested it twice at 13ppm and twice an hour later when I got 11pm.

 

[mknauss]

Wow -- good for you. I just sort of eyeball everything --------

 

[Richard320]

Maybe your pool isn't as big as you think? When you adjust pH, do you hit it right on, or overshoot?

 

[Elkie108]

Haha, I had an extra scale so why not?

Funny you say that about the pool size. I had been relying on the sized listed from my pool inspection sheet when I purchased the property in the fall. When I added alkalinity it spiked high and realized then my pool was closer to 12300 than 15000gal. I've been using the measurements 14x29 w/ depth of 3'-6' which I just measured again to double checked myself.

When the pool starts to depen past 3' the sides also start to slope at 3' depth rather than going straight downward like the shallow end, is that accounted for in poolmath when calculating size?

I have not yet had to adjust for PH

 

[Richard320]

Haha, I had an extra scale so why not?

Funny you say that about the pool size. I had been relying on the sized listed from my pool inspection sheet when I purchased the property in the fall. When I added alkalinity it spiked high and realized then my pool was closer to 12300 than 15000gal. I've been using the measurements 14x29 w/ depth of 3'-6' which I just measured again to double checked myself.

When the pool starts to depen past 3' the sides also start to slope at 3' depth rather than going straight downward like the shallow end, is that accounted for in poolmath when calculating size?

I have not yet had to adjust for PH

No. poolmath doesn't take sloped walls into account. Nor will it deduct if you have steps intruding into the pool.

 

[Elkie108]

No. poolmath doesn't take sloped walls into account. Nor will it deduct if you have steps intruding into the pool.

So I was playing around with poolmath, and in order to have even a 9ppm increase with adding 6.8oz of cal-hypo the pool would have to be 4k gal.

I whipped out the ol' graph paper and limited memory of geometry and with the help of google now estimate the pool to be 11k gal.

Even if thats off by, let's say 2k gal 6.8oz of cal hypo would only raise 4.1ppm.

Any other potential reasons?

 

[Richard320]

So I was playing around with poolmath, and in order to have even a 9ppm increase with adding 6.8oz of cal-hypo the pool would have to be 4k gal.

I whipped out the ol' graph paper and limited memory of geometry and with the help of google now estimate the pool to be 11k gal.

Even if thats off by, let's say 2k gal 6.8oz of cal hypo would only raise 4.1ppm.

Any other potential reasons?

Multiplying by the wrong factor when testing FC before adding?

Plenty of people get .2 and ,5 factoring for 25 and 10 ml wrong once in a while.

I'm out of ideas.

 

[jimbethesda]

The results are from your TF100 test kit?

 

[Elkie108]

The results are from your TF100 test kit?

Yes. Turns out Richard320 was correct and I was having a major brain malfunction and not multiplying out the number down to 6.5 ... ?