High CYA, low TA, what first?

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R

Rodex

Gold Supporter
Jun 2, 2019
304
Mansfield, TX
Pool Size
11000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool Edge-25
We bought our new house with a pool a few months ago, and we have never owned a pool before. I was testing with one of the Taylor kits and getting the extended tests at Leslie's until I found TFP and the TF100 kit that I just got in this past Saturday. First results are below. The water isn’t green or anything, but the CYA is a bit high and the TA is low. I started down this path because the TC from the Taylor kit always seemed either high or low. From looking through the forum, the high CYA seems like it could be from using the 3” tabs that Leslie’s suggested. If not those, what is recommended?

Where should I start - bring the CYA down first? Thanks for any help!

==========================================
Home
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Build Type: Plaster
Volume: 11000 gallons
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Latest Test Result Summary:
FC: 1.0 (10 hours ago)
CC: 0.5 (10 hours ago)
pH: 7.5 (10 hours ago)
TA: 60 (10 hours ago)
CH: 225 (10 hours ago)
CYA: 70 (10 hours ago)
==========================================
------------------------------------------
Test Results 06-02-2019 @ 09:30 AM
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Free Chlorine: 1.0
Combined Chlorine: 0.5
pH: 7.5
Total Alkalinity: 60
Calcium Hardness: 225
CYA: 70
 
You're very close. That's great. Welcome to TFP! Good to have you here :)

Overall, once you switch to liquid chlorine, most everything will come into line. Raise your FC to around 7 ppm, which is commensurate with your CYA level, per this chart: FC/CYA Levels The CYA will come down very gradually over time, and 70 ppm CYA is actually quite manageable.

That addition will also raise your pH just a little, which is needed right now. The trichlor pucks have been depressing your pH a little. The TA at 60 is a tad lower than our recommended levels, but many people like it right around 60, so I'd leave that as is.

You can rule out the presence of algae with this test: Overnight Chlorine Loss Test which is always a good step when taking over pool water management. Note that free-floating algae is invisible to the naked eye. By the time you see algae, you already have a lot of it.

Less urgent, but if it were mine, I'd also raise the calcium a little, to somewhere around 275/300. Along with all the other numbers in the correct range, the calcium helps protect the plaster.
 
My CYA is high and I dind't know why until marty posted this..Now I understand why they like Liquid Chlorine :)

Chlorine is a gas. It must be tied up with something. Solid chlorine is either Trichlor or dichlor, were it is ties to CYA, or Cal Hypo, were it is tied to calcium.

Liquid chlorine, aka sodium hypochlorite, the chlorine is tied to WATER.
 
Looks like Marty and I cross-posted. If anything sounds contradictory, just ask and we'll sort it out :) I agree with Marty there's a good chance you have free-floating algae, so the OCLT test is a good thing to do right now. Take the starting reading just before dark, with no sun on the pool, and after 30 minutes pump run time after adding the liquid chlorine.
 
mknauss said:
Welcome to the forum!
You can manage a CYA of 70, but, if you need to SLAM Process (sounds like it) it is easier at 30-40 ppm CYA. What does the water look like?
You need to use liquid chlorine exclusively with a high CYA. Follow FC/CYA Levels
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.
Click to expand...

Thanks! The water is clear, some days it’s bluer than others. I’ve seen a bit of green on the walls, then we brush and run the pump for a while and it’s gone for a few weeks.

Started reading through the ABCs, and I’ll do the OCLT tomorrow night and pick up some liquid chlorine. When I SLAM, I have the granular shock, but the site specifically mentions SLAMing with liquid chlorine. Was the granule shock a waste of $?
 
What is the granular shock?

Liquid chlorine is the way to chlorinate with the only side effect being added is water. Granular shock has either CYA or Calcium.
 
mknauss said:
What is the granular shock?

Liquid chlorine is the way to chlorinate with the only side effect being added is water. Granular shock has either CYA or Calcium.
Click to expand...
mknauss said:
What is the granular shock?

Liquid chlorine is the way to chlorinate with the only side effect being added is water. Granular shock has either CYA or Calcium.
Click to expand...

Power Powder Plus.

Ok, definitely will not be using it.
 

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As John mentioned it would be good for you to raise your CH a bit. So using the Cal Hypo will do that. Just track how much you add and use Effects of Adding Chemicals for how much CH that adds to your pool.
 
mknauss said:
As John mentioned it would be good for you to raise your CH a bit. So using the Cal Hypo will do that. Just track how much you add and use Effects of Adding Chemicals for how much CH that adds to your pool.
Click to expand...

For the OCLT, the instructions say to have the FC at least 3ppm, so I’ll need to raise it a bit. I bought Blue Whale liquid chlorine from the pool store, it says “sodium hypochlorite 12.5% other ingredients 87.5%”. I checked the offerings from Lowe’s and Walmart and both had the same verbiage. Any suggestion on how much to add to see the affect to bring it up to 3ppm? From the eBook, sounds like I’ll only want to add some every hour until it’s up to that level.
 
needsajet said:
Looks like Marty and I cross-posted. If anything sounds contradictory, just ask and we'll sort it out :) I agree with Marty there's a good chance you have free-floating algae, so the OCLT test is a good thing to do right now. Take the starting reading just before dark, with no sun on the pool, and after 30 minutes pump run time after adding the liquid chlorine.
Click to expand...

Got it to 3.5 ppm FC last night and tested this morning at 3.0 ppm. So, no need to SLAM?

If not, I’ll start targeting FC of 8 ppm. Thanks!
 
OK -- doing a OCLT at minimum FC for your CYA is not the best but go with it for now. Just raise your daily FC target to the 8 ppm.
 
mknauss said:
OK -- doing a OCLT at minimum FC for your CYA is not the best but go with it for now. Just raise your daily FC target to the 8 ppm.
Click to expand...

I’ve been adding the chlorine per the pool math app, and it’s not meeting the 8ppm - most I’ve achieved is 5ppm yesterday and today it’s down again to 2.5ppm. Is there any harm in going ahead and SLAMing? There was green mixed in with the silt at the bottom of the pool when I vacuumed today (I think the DE grid might have a hole in it).

pH went up to 7.8 but could that be from running the pump so much (aerating)?
 
Seeing green is all the reason you need to SLAM :)

Adding bleach temporarily raises the pH, so for your SLAM, an important step is to lower the pH before the first big addition of FC. I like to lower it to 7.2 myself, before starting a SLAM. The TFPC range is 7.2 to 7.5 before starting.
 

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