confused by test results

[garykli]

Hi,

I've a 27k gal pool w/ swg. It was maintained by pb for first 2 mo. the chemo levels seemed to be ok. I used the tf100 test kit. Now that the pb is no longer maintaining the pool, I measured Fc for the first time since the salt was added & got the following results:

FC 0.5
CC 0
CYA 20
TA 90
Ph 8.3
Salt 3400

Following the pool calc I added a gal of 10% bleach & about 20oz of cya to start... I tested FC the next day & still got a reading of 0.5... added another gal & tested again at end of day. It still reads 0.5... I thought maybe my reagent went bad so I diluted some chlorine in water & tested that. It read off the charts high...

Any idea why my pool FC is not moving at all?

 

[jblizzle]

Must be something in the water consuming the FC. Turn the SWG off, raise the FC level and do the OCLT to see if you need SLAM the pool.

Also until your CYA gets up, you are losing a good bit of FC to the sun, but that is not the main issue.

Get that pH down too. Leaving it that high will start to result in calcium scaling.

 

[Smykowski]

Must be something in the water consuming the FC.

Yup. SWGs can maintain FC in a clean pool, but they can't get ahead of something living in the pool. I agree, that fast of an FC drop points to needing to SLAM the pool.

 

[garykli]

Wouldn't my cc go up though?

 

[jblizzle]

CC are only one sign of a problem and do not always show up when there is a problem. The sun and FC break down the CC so you may not measure them.

 

[Leebo]

Keep in mind the test can show iffy results when the CYA is lower than 20. There's a good chance you CYA level is a around 0, thus the sun could consume the chlorine very quickly. Raise your CYA level up around 40 to help keep your chlorine levels at proper level.

To see if algae is consuming the chlorine, try an OCLT and see your results.

 

[garykli]

So I did the overnight chlorine loss test and sure enough, I lost the entire gallon... went from 3.5 down to .5... guess it's time to shock...

one part I don't understand is what happened to my cya... the pool was filled in Dec. at that time about 15lbs of CYA was added, cya was reading around 60 or so in jan, now it's reading <20... not really any new water, some rain, but that can't account for too much change over and hardly any use of the pool... any ideas where that went?

thanks!

 

[jblizzle]

We get some reports of CYA loss over the winter, although it is usually in closed pools where the FC drops to zero and a bacteria converts it to ammonia. This could be what is going on as the ammonia will consume the chlorine very quick (and usually CC show up).

In any case, the solution is following the SLAM process.

 

[Patrick_B]

I agree, ammonia will do a number on FC, and if you have it, you will see some CC. A lot in fact if you have a good amount.

 

[garykli]

I guess the CYA loss is still a mystery then since I still see 0 CC... I'm in day of 2 of the slam and am still losing chlorine pretty fast, whatever 'bug' is eating up better stop soon

 

[duraleigh]

Disregard even testing for cc's until you complete the slam......they are, for now, irrelevant.

The hard fact is your chlorine loss will only stop once you have killed all the organics in your pool. If you stop with the use of chlorine, the organics will come right back and you will never complete the SLAM process. A SLAM can proceed MUCH, MUCH longer than yours. More than a week, easily.

Keep the faith, follow the SLAM process to a T

You will win......promise.

 

[Patrick_B]

Two weeks plus is not uncommon at all. Every situation is different, some take a long time.