On 8/2 I tested at 75 CYA. Started to notice that my SWG wasn't keeping up so tested yesterday and got about 20. No backwash, no rain overflow, nothing unusual. What would cause such a massive and fast drop? I have been maintaining the pool for 9 years and don't think I have ever experienced this.
Huge CYA Drop
- Thread starter Cedarpool
- Start date
- Jun 24, 2021
- 16,315
- Pool Size
- 29000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
Post a full set of results FC, CC, pH, TA, CH, CYA.
Post your fill water TA and CH.
Heat, testing error, reagent, leak, bacteria.
Heat: What has been the average pool temperature over that time?
Testing error: How are you performing the test?
Reagent: While the CYA reagent is the most stable, it may be the reagent is bad.
Leak: Do you have an autofill? Has your water usage increased? Has any other chemical level dropped?
Bacteria: Someone will chime in, but I don't think it is this, but possible. I would expect that CYA would go to 0 if you had bacteria, additionally chlorine would kill the bacteria.
www.troublefreepool.com
Post your fill water TA and CH.
Heat, testing error, reagent, leak, bacteria.
Heat: What has been the average pool temperature over that time?
Testing error: How are you performing the test?
Reagent: While the CYA reagent is the most stable, it may be the reagent is bad.
Leak: Do you have an autofill? Has your water usage increased? Has any other chemical level dropped?
Bacteria: Someone will chime in, but I don't think it is this, but possible. I would expect that CYA would go to 0 if you had bacteria, additionally chlorine would kill the bacteria.
Degradation of Cyanuric Acid (CYA)
This thread explores some of the ways that Cyanuric Acid (CYA) can degrade since many users report seeing CYA drop under various conditions. CYA Degradation by Bacteria Some pool users find that their CYA levels drop over the winter when their pool is let go (i.e. no chlorine added). Many of...
www.troublefreepool.com
FC 4, CC 0, TA 100, CH 325, Salt 3400. Water temp on 8/2 84, yesterday 81. Same bottle of reagent was used on 8/2 and yesterday with an expiration of 9/2025. No autofill, one top-off in the last month due to evaporation. I always perform the test the same way, outside, back to the sun.
- Jun 24, 2021
- 16,315
- Pool Size
- 29000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
Only other thing I can think of. When you mix the reagent, let it sit for 2 minutes before filling the tube to perform the test. Try that and see what happens.
Other than that, bacteria or act of God.
If I missed something, someone else will pipe in...
Other than that, bacteria or act of God.
If I missed something, someone else will pipe in...
- May 3, 2014
- 62,719
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
Most likely testing error - either test.
Otherwise, a one off oddity.
Otherwise, a one off oddity.
I am going to shock tonight taking advantage of the low CYA so that should take care of any bacteria. I will then will start adding CYA to bring it back up.
I'm convinced that high water temps have something to say. My water temp has been 90-96F (no heater) since June and even though I've been adding a lot of dichlor pucks and shock (no hate - leftover supply to raise CYA and spare my SWCG), my CYA has stayed steady at 60ppm. Browsing the forum it seems other have had a similar experience.
- May 3, 2014
- 62,719
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
You can lose 10-15 ppm CYA per month with elevated water temperature, but not 50 ppm plus.