What is the purpose of Trichlor Tabs ??

[jsaldi]

A few years ago we had algae problems, despite keeping the chlorine up, and thanks to this pool forum(no help from Leslies) it was determined that my CYA levels were really high. Problem was solved over a couple years, running the chlorine levels high, getting a good test kit and gradually diluting the water.
Fast forward a few years, and darnit we did it again! We started getting some algae in spite of good chlorine levels and I tested the CYA today and sure enough it was about 100. A few months ago it was at 50. I didn't realize the pucks my husband bought from a coworker(with a pool biz on the side) contained CYA. I know how to deal with it this time, but my question is:
What is the purpose of the trichlor pucks if they keep adding CYA to your pool? I use bleach, but we keep pucks in the floater as well. Not any more though!
IG Pool, PebbleTec, @20K gal

[Watermom]

Trichlor pucks can be useful if your CYA is low. But, as you know, over time they add CYA and you have to stop using them. A lot of people use them when they go on vacation. You have no idea how many people come to the forum because of the very problem you have had --- getting algae despite having what they think is an adequate chlorine level. Not too many people, pool stores included, understand the connection between CYA and chlorine.

What kind of test kit are you using? A CYA reading of 100 doesn't necessarily mean 100. It can actually mean 100 or any number greater than that. Dilute a sample -- half pool water, half distilled water -- and then run the CYA test with that mixture. Multiply the results by 2 and then report that CYA reading here.

[CarlD]

Like anything, Tri-Chlor pucks when used correctly can be beneficial. Tri-Chlor adds about 6ppm of CYA for every 10ppm of chlorine. You can't prevent it--that's how Tri-chlor is made. It also is HIGHLY acidic and can severely lower your pH. When is this good?

An example many new hard-sided pools, while curing, tend to have a steadily rising pH, need Chlorine, and have not CYA yet. Pucks fill all three needs, perfectly

In fact, in any high-pH, low CYA situation, Tri-chlor tabs can be an all-in-one solution. But only temporarily and with regular monitoring of pH and CYA levels.

Di-chlor powder puts out more CYA but is less acidic.

In in a low pH, high CYA situation, bleach works. Cal-hypo can work, but only if the calcium hardness isn't high as well.

But you can just use the bleach and add Muriatic or Dry Acid + CYA powder as well.

[jsaldi]

I have the Taylor K2006 kit. I tested the CYA undiluted first and then when I saw it was over 100 tested it diluted 50/50 and it was about 90.
I shocked the hell out of it with the HTH Super Select 56% sodium hypochlorite, two bags yesterday and one today and will test the chlorine tomorrow. I use bleach normally but keep the HTH around for heavy rains, etc.The water looks clear but hubby said he saw algae . My PH jumped up since last week to 8.2, which is unusual because it has been pretty steady for several weeks, so I added some muriatic acid today.
When I had the high CYA problem years ago, I remember all too well that the pool store kept telling me everything was good. Thank goodness I found this forum and got it all straightened out!
I will be more careful with the Trichlor from now on!

[CarlD]

56% Sodium Hypochlorite? in a powder????? That doesn't sound right. Sodium hypchlorite is Bleach or liquid chlorine, in a brine solution, and never is more than 14%.

[BigDave]

I have the Taylor K2006 kit. I tested the CYA undiluted first and then when I saw it was over 100 tested it diluted 50/50 and it was about 90.

Sounds like that means CYA = 180. No?

I shocked the hell out of it with the HTH Super Select 56% sodium hypochlorite, two bags yesterday and one today and will test the chlorine tomorrow.

2lbs calcium hypochlorite would add a little less than 7ppm FC to 20,000gallons- not nearly enough to shock at 90ppm CYA much less 180ppm CYA.

[JimK]

You mentioned pH jumping suddenly.....keep in mind high chlorine levels can give you a false high pH reading.

[CarlD]

Sounds like that means CYA = 180. No?


2lbs calcium hypochlorite would add a little less than 7ppm FC to 20,000gallons- not nearly enough to shock at 90ppm CYA much less 180ppm CYA.

BigDave, I think you are right: jsaldi meant calcium hypochlorite, when he said sodium hypochlorite. Aka, Cal-Hypo.

[jsaldi]

Sorry I did mean Calcium Hypochlorite. So I have put 3 1 lb bags in 56% each bags in. I will test again in a bit and repost. I tested the PH before adding the third bag of shock.

[jsaldi]

OK I tested with my Taylor kit then took samples to a local independently owned pool as well as Leslies. All are close by my house so I would say all testing was done within 30 minutes..
My numbers:
TC: 10
CC: .2
PH: 8.2
TA: 70
hardness: 400
CYA 180(diluted 50/50 multiplied by two)

Next was small pool store:
TC 12.33
CC:0
PH:7.9
TA:46
TA(adjusted) 13
hardness: 438
CYA 100
He said his cya test went up to 300, that high CYA was skewing the TA, to take 1/3 of CYA and subtract it from TA to get adjusted TA.
Recommended draining the pool by 1/4 and adding baking soda I had on hand which is about 8 lbs.
He said I should drain the pool 1/4 to lower the calcium and CYA.

On to Leslies:
TC:10
FC: 10
PH: 7.6
TA:80
CYA: 100
hardness: 250
He said everything looked good. I questioned him about the high CYA and he said it was OK to run the pool at high CYA, up to 300.
Also my husband wanted to know if we should backflush the DE filter, even though pressure is good, because of seeing algae. I think someone told him algae could be in the DE inside the filter.