CYA Gone?!?!

[Petebacher]

I'm opening my pool late this season - uncovered it last night and started a SLAM this morning.

When I closed up last year, CYA was at 44. I drained 15% of water last fall, and added it back last night. By my calculations, CYA should be around 37, but when I measure, I'm getting LESS THAN 30 (water is nearly clear and the black spot doesn't even look dim at a measurement of 30!). FC is dropping like a rock in bright sunlight, which is consistent with very low CYA; a few hours ago I had FC up to 20 - just now it was 4.

Oh, and my CYA reagent is date stamped good through 12/2018, and was kept in the room temperature basement all winter.

I am under the impression that nothing reduces CYA aside from replacing water. The majority of my water has not been replaced. What gives?

-Pete
Just west of Philadelphia, PA

 

[mknauss]

CYA can naturally degrade when exposed to UV and chlorine. It also can be consumed by a bacteria (normally seen in winterized pools) that has a by product of ammonia.

Do a quick test. Add enough LC to get to 10 ppm FC. Circulate pool for 30 minutes. Test FC, if at 5 ppm or less you have ammonia. Keep doing that cycle until your FC after 30 minutes is above 5 ppm.

Then add 30 ppm worth of CYA powder. Add the CYA by using what we call the sock method. Get an old sock (no holes) and put the measured amount of CYA. Tie the sock closed and either suspend it in front of a return (hang it from your brush pole works with something weighted on the deck) OR if it still allows flow thru the skimmer, place the sock in the skimmer. Every 15/20 minutes give the sock a squeeze to speed up the process. Please DO NOT follow the directions on the container of CYA to just pour it into the skimmer and don't put the sock in the pool as the CYA is acidic and can bleach/stain pool finishes.

How are you testing your pool water chemistry?

 

[Petebacher]

Very helpful, Marty - thanks!

I have a Taylor K-2006 test kit with the "black spot" CYA tester and bought a separate, larger bottle of reagent last year as I was having CYA issues (too high!) after using chlorine powder when opening my pool.

I'll try the 30 min FC test now... I hope my local cheap-o pool supply place has CYA! Else maybe WalMart...

-Pete

 

[Petebacher]

FC was good after 30 mins (I had gone through 15 bottles of 10% LC at that point, each of which normally raises FC by 3...), so I picked up some CYA and Trichlor at Walmart - both are in now - hopefully FC remains stable overnight, though I smelled CC just now when I measured FC - should have checked CC too. Will do so in the AM.

Thanks again for the help!

-Pete

 

[mknauss]

I bet you had ammonia and the first 15 bottles cleared it.

Smelling CC is good. The chlorine is killing stuff ----------

 

[Petebacher]

Good morning -

Filter and robot ran all night long (and are still running). Chlorine was stable overnight and this morning the water is crystal clear. DE filter pressure is up several PSI from initial charge early morning yesterday which makes sense - bacteria and algae that had produced minimal cloudiness yesterday are now mostly in the filter.

I measured CYA this morning and as expected I'm a bit below 30, so I dropped in two trichlor tablet floaters and will monitor both FC and CYA over the next few days until I figure out what FC levels do during full sun. I plan to maintain SLAM FC another day and do some additional brushing today just to provide an additional margin of safety against algae.

Oh and no CC smell this morning!

Thanks again for your help!

-Pete

 

[JoeSelf]

Don't forget to do OCLT test to end slam.