CYA not measureable?, TA high, ph Low

[eswenson]

I've got a 40,000 gallon pool with a CYA level that I can't measure (I'll explain), a TA that is now about 140ppm, and a ph that is 6.8 after adding Muriatic Acid to reduce the TA.

First, the CYA. I'm wondering about the Cyanuric Acid Reagent (R-0013) I purchased in a large bottle from Taylor. I ran out of the reagent that came with my Taylor K-1005 test kit so ordered more online. I used it the other day to measure my CYA and was unable to get the black dot at the bottom of the view tube to disappear after filling the tube completely with solution from the bottle. My view tube has its highest (lowest numerical value) at 30ppm. I don't know what this means, especially since before I got the new R-0013, but last year, I measured it at over 100ppm and went on a strict regimen of only liquid chlorine. But now, with a reading of under 30ppm (can't go any lower), I don't know whether the reagent is working or whether I really have a CYA level that low.

The TA, on the other hand, was about 170ppm when I tested it two days ago. I bought 2 gallons of Muriatic Acid, and poured all of it in my pool. The TA is now about 140ppm, so it probably helped. My test kit says that I need TA between 80-120, so my inclination is to buy more Muriatic Acid and add some more. However, prior to adding any Muriatic Acid, my pH was good. It was between 7.2 and 7.4. Now, my pH is 6.8.

What is the recommended order that I should try to fix things? I'm assuming I should get the TA under control first, then raise the pH and hope I don't raise the TA in the process. Then add chlorine (which is reading 0 and not "sticking" very long when I add 8 gallons of liquid chlorine, as I did a few weeks ago).

Also, how can I be sure that my CYA is actually good (and that I didn't purchase a reagent that was bad?

[doug]

cya of less than 30 not effective and stabilisation between 30 and 50 ideal range the higher you go the less effective the chlorine will be 100 will possibly lead to chlorine lock depending on chlorine type cyanuric acid will have some effect on ph but should be no problem to control 450grs acid for 10000 gals will raise reading by about 10ppm

[Denniswiseman]

See if the reagent has an expiry or manufacture date on it to check although it is chemically inert and should last for years
Get your PH up by aeration, spray the water in to the air in an arc (I tend to use a large pond aerater)
When it increases reduce the TA more with muriatic acid and then continue aeration
Check your CYA as high CYA renders the chlorine in effective

[eswenson]

I actually bought a test kit to test out my CYA measurement and proved that my testing is accurate, so I really do have exceedingly low CYA levels (below 20). So how do I raise the CYA level? I've tried using dichlor tablets instead of liquid chlorine for a couple months now, but the CYA level is still below 30.

[Denniswiseman]

That's very strange after using Dichlor for a couple of months your CYA should be sky high
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.
If you previously had a reading of 100ppm and the only way to reduce it is by partial drain and refill and you have been adding Dichlor since, I very much doubt that your CYA is that low and in fact the opposite
Can you check the Dichlor label for the ingredients and percentage as you may be using a low dosage

[eswenson]

I guess I was wrong. I have been putting trichlor tablets (HDC 99% 3" trichlor) in a floating container in my pool for the last couple months to try to raise Cl and CYA. I just measured pool chemistry today (haven't done it in 3 weeks) and found Cl=0ppm, pH=8.2, and TA=150. CYA was <20ppm. So I'm planning on adding 2 gallons (pool is 36,000 gals) of muriatic acid to reduce the TA and pH first. Then I'll re-measure. If TA/pH have been reduced to appropriate levels, I will work on the CYA and then Cl. Is it best to add Cl + stabilizer (dichlor/trichlor) to get the CYA levels up, or should I just add Cyanuric acid until my CYA levels are good -- and then work on Cl? -- Eric

[Denniswiseman]

If you use cyanuric acid to raise your CYA it's more controlable and instant although wait 24hrs to let it mix properly unless it's a liquid
Your chlorine level will be relative to your CYA although I would get some liquid chlorine in right now to prevent algae bloom ( a cya of 20ppm would require 3-5ppm chlorine with a shock of 10ppm)
Chlorine / CYA Chart
Use Pool Maths to work out volumes required
How come your ph was 6.8 and is now 8.2. What have you done to raise this

[eswenson]

Ok, I'll get some cyanuric acid to try to raise the CYA. I'll put some liquid chlorine in in the mean time.

I have no idea why pH has gone up. I had previously put in muriatic acid in order to lower the TA -- and that probably would have lowered the pH too. After that, my pH was 6.8. Nothing else but trichlor has gone in since the pH of 6.8. What causes pH to go up on its own? What is your recommendation on the order I should tackle these issues?

Cyanuric acid to raise the CYA, muriatic acid to lower TA and pH, then liquid chlorine?

-- Eric