Very Persistent Algae

I have to admit, this has me quite perplexed. This is my 2nd season with the pool (24' above ground) and about halfway through last season I started with troublesome algae. Local pool stores have really not been much help. I'd like to adopt the BBB method and get this pool squared away, not much fun having a pool when you fight with it constantly.

So the persistent algae, which tends to show up on the steps esp., and the bottom, seems to be able to withstand high doses of bleach. I'm using test strips as I don't have a taylor kit (yet), but according to the strips, and the pool stores that have analyzed the water, it all looks good.

Last season I used Tri-Chlor 3" pucks and I think part of my problem was high CYA rendering the Chlorine ineffective, this year I'm trying to keep away from the pucks and my CYA is steady around 40-50.

I shocked the pool a few days ago (5L of 10% bleach) and yesterday I vacuumed, and backwashed. It's about 3pm and I have green on the bottom of the pool. I'm going away for the week, so I'm planning on hitting the pool with another 5L of bleach tonight.

Any advice is greatly appreciated

With a CYA of 40-50, your shock level is 15ppm. A liter is approximately 1/4 of a gallon so that means if you are adding 5L of 10% bleach, you are adding about 1.25 gallons which would add about 10.4ppm of chlorine. (For reference, each L will add 2ppm of chlorine. use that as a reference to help you figure out doses to add. Try and keep the chlorine at 15ppm as consistently as you can.) Once you get this cleared up, you'll want to keep the chlorine between 3-6 ALL the time or else the algae will come back. Read the Best Guess Chlorine Chart in my signature below for more info about the correlation between CYA and chlorine.

You are going to have to get a good test kit. We recommend the Taylor K-2006 or 2006C but Taylor kits cannot be shipped to Canada, so you'll have to order from the Canadian distributor. It is Lowry's or something like that. I'm going to have to check.

In the meantime, go to Walmart (I think you have Walmarts, right?) and see if they have the HTH 6-Way kit (not test strips). If not, get a cheap OTO/Phenol Red (yellow and red drops) to use. Either of these will only test to 5ppm but you can force it read higher with a dilution method. Take one part pool water and mix it with one part distilled water, test and multiply the results by 2. If you need to read higher than that, take one part pool water and two parts distilled water, test and multiply the results by 3. Each dilution loses a little accuracy, but it is better than nothing.

Post a current set of numbers when you get them.

Brush the pool daily and backwash your filter whenever the pressure rises 8-10 psi over clean filter pressure.

Please fill in the following pool chart with the information about your pool. This makes it easier for us to help you.

Pool Chart Entry Form
Pool Chart Results

Hope this helps. Welcome to the Pool Forum!