CYA disappearing and CC on way up

[PolareNJ]

I started using the TFP methodology last year and am comfortable using the TF-100 test kit. We are 'lucky' enough to have the special bacteria that consumes CYA over the winter, which was a blessing/nightmare last year when the process resulted in extremely high ammonia readings. We got thru that and kept the CYA at around 40 last year, resulting in a much lower ammonia reading of 0.5 - 1.0 ppm ammonia when we opened the pool this year and <20 ppm CYA. The ammonia level disappeared to 0 quickly. The pool cleared in 18 hours and has been sparkling ever since. We managed to get the CYA up to about 25, and we have been SLAMing for 10 days. I've kept the FC at 12-15 and got the CYA up to 25. However, I haven't been able to get the CC down lower that 1 (2 drops using TFP-100 test kit), so we keep SLAMing. We've added stabilizer in low doses over a few days, and tested the CYA this morning and it is back below 20 ppm and the CC has increased to 1.5 - 2.0. I'm concerned that the CYA eating bacteria is still present even after high FC levels for 10 days and that by adding more stabilizer we are feeding the CC. If so, we have a vicious cycle. Any thoughts/advice?

Other metrics: TA is 90 and pH was 72-75 before SLAM. Pool is in sun 12 hrs a day and water temperature is now 78 degrees. Less than an inch of rain since opening pool. The only other possible issue is a relatively high phosphate reading of 880, but I've read that this can be controlled with good chlorine levels.

Thanks for any help.

 

[flygirl516]

(Disclaimer: I am no where near a pool expert like many of the folks here, but I'll try to help!)

How often do you check your FC level? And how much FC are you losing?
How are you adding your CYA?

To rule out ammonia, try this:
Treatment for Ammonia:
1. Begin a SLAM and dose FC up to SLAM level. Do not add additional CYA at this point.
2. Retest FC at 10-minute intervals.
a. If FC loss is greater than 50%, add FC to bring back up to SLAM level and continue retesting FC @ 10-minute intervals.
b. IF FC loss is 50% or less, add FC to bring back up to SLAM level. Go to Step 3.
3. If CYA is below 30 ppm, add enough CYA to bring level up to 30 ppm.
4. Continue SLAM as directed in the SLAM article until the SLAM Criteria of Done are met. Test as directed in the SLAM article - no longer need to test FC at 10 minute increments at this point.

Someone may have a better explanation for CYA loss. I did a quick search and didn't see anything obvious though.

As for your CC level, you're still fighting something. Are you brushing daily? Have you gotten in your pool and scrubbed behind ladders, stairs, skimmer basket, etc?

 

[duraleigh]

One step at a time. If you have ammonia still present in your pool, Your FC will disappear down to zero in about 10 minutes. Is that your case?

 

[PolareNJ]

Thanks for your responses.
Duraleigh: The test strips show no ammonia at present (down from 0.5 - 1.0 ppm when we opened pool) and FC has been over 11 ppm with no bottoming out. Just can't get CC down to 0.5 ppm.

Flygirl516: We are generally holding FC levels of 11-15 ppm and have been since SLAMing started. FC (and CC) has been the same at the 11 p.m. reading as at the 6 a.m. reading. Testing at least four times a day at this point as FC is not being completely depleted. During the day, more FC is lost (due to lack of CYA and long exposure to sun). So we have passed two of the criteria to complete the SLAM: clear water and a loss of <1ppm of FC using the overnight test.
CC levels have remained at 1 ppm for the past ten days of SLAMing. CC level went up to 1.5 ppm at 6 a.m. this morning and 2.5 ppm
at 10 a.m. and the new CYA reading showed that the CYA has decreased from 25 to about 20.
Filter running all night. Because we are SLAMing at a higher dosage (15 - 16 ppm), the increased CC has not resulted in a FC of < 11
ppm.
Water sparkling clear.
Using stabilizer from pool store to increase CYA and today added three Tri-clor tablets as a last resort to add CYA and keep FC up
during the day. These are removed in the evening.

I understand that we have an unusual situation because of the disappearance of CYA every winter and am wondering if our inability to increase the CYA is due to our CYA eating bacteria. Does anyone have any experience with this?

 

[Texas Splash]

Your loss of CYA could be a result of what you describe at type of anaerobic bacteria, coupled with average monthly loss and any water exchange. One of the biggest impacts of CYA loss is how the pool was closed. Either way, it's not uncommon for those who winterize each fall to experience CYA loss over the winter. Each location (even within the NE region) and environmental factors of the pool impact that loss. As long as you are able to hold FC in the spring to rule-out ammonia, simply increase CYA and adjust as necessary.

 

[PolareNJ]

Thanks, Texas Splash. Our problem was maintaining the CYA, but we may have resolved that.

Update: Our readings this morning (6 a.m.):

FC = 17 (down from 18 at 11 p.m. last night)
CC = 2 (4 drops using the TFP-100 test kit), same as last night's test
CYA = looks like 28, so this is better than yesterday morning's 20 or less.
Water still sparkling clear.
We'll monitor FC during the day and try to keep it at 16, (well above the 12 needed for CYA <30). Really need to break this CC. We'll increase brushing of sides to find anything that may be hiding.

Here's hoping! I'll report back.

 

[PolareNJ]

Here is our update. While away for five days, we used the Tri-chlor pucks in the old chlorinator and the CYA is now up to 40. We have switched back to liquid chlorine. Our issue was that testing continually showed that the CC was between 1 and 2 (2-4 drops using the TF-100 test kit). This was confusing as the water passed the overnight test for FC. I had to pick up more chlorine at the pool shop today and had them test the water. It showed a CC of 0.08! Got me to thinking of what, if anything, could be compromising our test. All the solutions were new this year, but I was using the "Chlorine only" vial from last year. The vial had been cleaned after every use, but had a very slight discoloration. And that seems to have been the problem. When I used the new "Chlorine only" vial I ordered this year, the CC =0. I did 2 sets of tests again using the new and old vials, and the results were the same: Old vial showed CC and new vial showed no CC. Problem solved (knock wood). I knew we had to order new solutions at the start of pool season, but didn't know that the old vial (obviously with contaminants) would cause problems. Lesson learned.

 

[Texas Splash]

Glad you made progress. Have you tried cleaning the old tube with straight bleach? That's what we recommend as needed. Let the bleach sit in there for a few minutes then rinse it out. Might help.

 

[PolareNJ]

I had cleaned the vial as directed last year, and quite honestly, the problem might have occurred this year when we were testing so often. We're using the new vial and the old vial is soaking in bleach now, and we will use this as a back-up if needed. The vials themselves are not expensive and I'll probably buy a new one every year in the future.

Thanks for your help.