Is This Normal? Rapid Loss of FC...

[GoGrabTheNet]

Here in Phoenix, the sun is hot...darn hot! It is for this reason I hope to have a few locals chime in to give their feedback on the issue(?) that I'm experiencing.

Just getting out of a SLAM of 10 days, which was a royal PITA because of the sheer cook-off of FC during the day. So far, the water is crystal clear and the OCLT test proved that 0 PPM FC was lost and CC's were 0. It all originated when my Stenner pump went dry and then the tube failed. I had green algae (small bits) growing on the tiles in the skimmer and also some brownish/green algae growing on some of the walls.

Anyway...this morning's test, before the sun hit the pool, put the chlorine at 27.5 PPM FC and 0 PPM CC. I just tested the water now, and the results were 20 PPM FC and 0.5 CC. That's a loss of 7.5 PPM in about 9 hours! Sun is pretty intense today. Weather app on the phone reports "very high" UV index.

So is a loss of 7.5+ PPM a day normal? I don't recall this craziness last year, but then again, I wasn't SLAM'ing the pool. I have read here that higher levels of FC tend to dissipate quicker.

I should also mention that the pool is a warm bathtub. Water temperature is about 96 degrees.

Other test results:

CYA: 55-60
TA: 110 (seems to have shot up from my previous 90 due to adding tons of chlorine?)
CH: 350
pH: Waiting for FC levels to drop before measuring again. Last time I checked before SLAM'ing, it was 7.8'ish. Midway through the SLAM, I added about 16oz of MA.

Thanks!

 

[Jimrahbe]

go,

I'll let some better chemical guys chime in, but I believe that when the FC is really high, it burns off at a much faster rate then it would if it were in the normal range for your CYA...

My initial thought is that what you are seeing is normal..

Let's see if we can get some of your Arizona buddies to answer up...

Thanks,

Jim R.

 

[mknauss]

You will be fine. At high FC it degrades alot in our sun. Use your CYA at 60 and balance out at 6 FC or so for your minimum.

Liquid chlorine should have no effect on TA. Probably your fill water with out your normal acid adds during the SLAM. Might want to get the TA down after things balance out.

Take care.

 

[GoGrabTheNet]

Thanks, Jimrahbe and mknauss. Having FC at 27.5 PPM then 20 PPM is still rather high. Hopefully, FC usage will go down once I get back to normal ranges. I'll probably be targeting 8-9 PPM just for a little extra margin of safety. Overall, it will be a challenge to dial in the Stenner to keep up with the demand. It will need to run multiple times a day just to keep the FC levels from swinging widely over a 24-hour period.

 

[mknauss]

If you are comfortable that your pool is organic free take your CYA to 70 or 80. Almost treat it as a SWCG chlorinated pool as you are dribbling in chlorine multiple times a day.

The FC loss will drop quickly in September. Be ready for that.

Take care.

 

[GoGrabTheNet]

If you are comfortable that your pool is organic free take your CYA to 70 or 80. Almost treat it as a SWCG chlorinated pool as you are dribbling in chlorine multiple times a day.

That's just the thing! Right now, I must trust my OCLT results and have faith that it proves the pool is organic-free. The last thing I want to do is redo the SLAM process again!

As far as CYA, I'm not going any higher until I confirm my measurements up to this point. CYA dropped over the winter, and I've been slowly increasing it with stabilizer granules. I've measured CYA several times, each getting a different result! I got some 50 PPM Standard solution in the mail early last week, and it completely threw off what I thought would be an accurate result! Therefore, I ordered a second CYA Viewing Tube from TFTestkits so I can do a side-by-side comparison between my pool water and the 50 PPM CYA standard solution. We all know the test is subjective, and it seems that any variation of lighting conditions, even outside, has a HUGE impact on the visibility of the dot.

 

[mknauss]

The one thing that helped me on the CYA test was suggested by KimKats I believe.

Mix your solution and shake, let sit a couple minutes, shake. Fill to 100 line, glance for the dot, if you see it, fill to the 90, glance, etc.

It is the glance that helps. If I stare at the dot, I will see it no matter what!

 

[GoGrabTheNet]

It is the glance that helps. If I stare at the dot, I will see it no matter what!

Agreed! Good advice. I will try the "glance technique" and go line by line.

 

[Akathisia]

+2 on the KimKats CYA method. It's helped me too.