CYA Help Please

[TEXASERIC]

I have a in ground plaster/gunite pool approx. 17,000 gal. The pool is less than a year old, and I think my CYA levels are already high. Is this possible? I use tri-chlor tablets, and I know they sluff CYA but I was under the impression that it would take years. I am currently in the 80-85 range as best I can tell with the TF-100. I have never added stabilizer other than what is in the tablets that I know of, so dont know where its coming from. I don't want to have to drain/fill my new pool, especially since it is finally getting to be the perfect time for using it. My current numbers are:

FC - 10
CC - 0
TC - 10
Ph - 7.2
T/A - 70
CH - 230
CYA - 75-85 best I can tell
Temp - 88

I know the FC is high, but I juiced up the chlorinator to get rid of a few little algae spots after I hit them with the brush. Guess I should stick with liquid bleach when I need to raise the chlorine a lot instead of using the chlorinator? Any help with this would be great. I guess my big qestion is; is it possible for CYA to get that high that fast?

Thanks,
Eric

 

[JasonLion]

Yes, it certainly is possible. Trichlor adds 6 ppm of CYA for every 10 ppm of chlorine. If you are adding 2 ppm of chlorine per day (fairly common), that would be 67 days to get CYA up to 80, assuming no water replacement at all. There is always some splash out, so in practice it will be longer, but even half a season is long enough for CYA to get problematically high.

 

[TEXASERIC]

So how do you prevent it? Abandon the chlorinator and use bleach? hate having and paying for equipment and not being able to use it. Thanks

 

[JasonLion]

So how do you prevent it? Abandon the chlorinator and use bleach?

Bleach or a SWG, or replace water frequently.

 

[TEXASERIC]

So instead of a drain/fill to lower CYA, how about a feed and bleed? Will it work? Do that many people drain and fill their pools 4 or 5 times per year? If so that is crazy. This is my first pool, but many family members had pools when I was growing up and never remember seeing them drain and fill. Thanks again

 

[JasonLion]

If you have an undersized sand filter, which needs to be backwashed frequently, that can be enough water replacement to keep things under control. Undersized sand filters are amazingly common.

 

[TEXASERIC]

negative, 400sq.ft. cartridge filter. Guess I will try draining a little then refill and see where I am, like I said dont want to start from scratch right now.

 

[TEXASERIC]

also have ozoneator if that matters.

 

[chem geek]

Some pools are naturally low in algae nutrients (phosphate and nitrates) while some people use algicides or phosphate removers. These can all let one get away with higher CYA levels and not get algae growth. The most straightforward way to manage the CYA level is to use primarily chlorinating liquid or bleach which will increase neither CYA nor CH levels. It is less convenient since you need to add chlorine every day or two (unless you have an automated dosing system such as The Liquidator, peristaltic pump, or SWG), but it's what most people do on this forum and keep their pools free of algae using chlorine alone. It's also a lower cost approach.

As for the ozonator, that only helps to prevent algae that is free-floating and circulates to the ozonator, but it does nothing for algae that clings to pool surfaces. Also, unless your turnover rate is fairly fast, a good portion of the water doesn't get circulated faster than algae doubles in population.

If you have winter rains that dilute the water, then you can start out using Trichlor in the early part of the season if you want and then switch over to chlorinating liquid or bleach later. So long as you know the effects of various chemicals, it's up to you how you want to manage your pool.

 

[TEXASERIC]

Is there a tablet that I can put in my current feeder that wont raise CYA? Currently using Ram 3" trichlor tablets. Thanks

 

[JasonLion]

No. There are special feeders that will work with cal-hypo tablets, but they are designed differently.

 

[chem geek]

(wrote this when Jason was posting)

No. Only Trichlor tablets can be used in that feeder. The only other type of tablets are Cal-Hypo but they dissolve much more quickly and require their own type of feeder (and putting Cal-Hypo into a feeder that was used for Trichlor can result in an explosion so do NOT do that). Cal-Hypo not only dissolves too quickly, but the tablets tend to fall apart near the end and there is leftover binder residue. This is why the granular/powdered form of Cal-Hypo is the form more typically used. Also Cal-Hypo increases the Calcium Hardness (CH).

The chemistry of chlorine compounds unfortunately is such that there isn't a slow-dissolving tablet form that doesn't add something you don't want to accumulate in the pool. However, there are automated systems for dosing sodium hypochlorite (i.e. chlorinating liquid or bleach) including The Liquidator and peristaltic pumps. There are also saltwater chlorine generator systems that generate chlorine on-site from salt in the pool.

 

[TEXASERIC]

Thanks for all the help guys. I guess for now I will try to lower the CYA levels and chlorinate with bleach until I figure out and research the best system for my needs.