Algaedyn working less effectively than previous years

[rocks911]

I started using Algaedyn two years ago and was blown away by its effectiveness. It was so effective that the only reason I needed to chlorinate the water was for sanitizing it. I could let the chlorine level go to just about zero and there would be no hint of algae.

Last year I repeated its use and it was not quite as effective. This year even less effective. I cannot for the life of me figure this out.
I have an 18,000 gallon pool and the rate of use for Algaedyn is a quart/20,000 gallon pool. I used 1 full quart for the initial treatment and have since run through more than another quart with additional treatments. I keep the chlorine at acceptable levels but the pool has green algae.

At $100 for 3 quarts I need this to be more effective. Any thoughts would be appreciated.

 

[pooldv]

My guess is that your CYA has been going up every year and reducing the effectiveness of the chlorine.

Here is the theory on how to maintain chlorine.
In order to keep the pool sanitary and not let algae grow the FC must be maintained at all times. FC level is set based on CYA and the [FC/CYA][/FC/CYA] chart. Keep it at target or a tad higher if needed. Never let it drop below minimum or the pool will be unsanitary and algae will start growing.

 

[rocks911]

My guess is that your CYA has been going up every year and reducing the effectiveness of the chlorine.

I appreciate the reply. When I first started maintaining a pool I did just that, let the CYA get entirely too high. I had to drain the pool and refill and do a lot of learning. This site was a great source of info. I have kept the CYA under control the last few years by using bleach mostly to chlorinate. In fact this spring I started to use granular exclusively because the CYA level was incredibly low. Now everything, with the exception of total alkalinity, is within normal limits. Maybe the alkalinity is a problem, it is very low, with all else being in range. I brush daily but still green algae. Not a lot of green algae but enough to annoy me because goodness knows I have been diligent in pool care, so its kinda frustrating.

 

[Donldson]

How are you testing? Can you please post up a full set of results and what you used to get them?

Silver is an effective algaecide but nothing is as effective as chlorine. If you maintain your FC level to the FC/CYA chart then you will not get green algae. If you keep a lower FC level and use supplemental algaecides as you are now then there isn't much we can advise you to do except to raise your FC level.

 

[pooldv]

I can say that the TA is not the issue. I also think some results might help.