Adding CYA to a Pool

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  • Post last modified:April 11, 2021
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Adding CYA (Chlorine Stabilizer)

Up until a few weeks ago, on the rare occasion when I’d need to add CYA (CYanuric Acid / chlorine stabilizer / conditioner) to our pool water, I would go to Leslie’s and get their liquid conditioner. It is be pretty much instant mixing. No need to wait a few days for all of the stabilizer to dissolve like when using the granules. The downside, of course, is that the liquid instant conditioner is much more expensive.

In the interest of saving money, I decided to finally give the dry stabilizer a try. On my monthly trip to pick up muriatic acid to control our pH, I also picked up a four pound bucket of the dry stabilizer granules. I also then set out on a research mission as to what the best way is to add these to the water.

First things first: a quick note on adding CYA – this is not something you want to overshoot. Start with half the amount you think you need, and then add more later if you need to. If you end up with too much, the only reliable way to lower your CYA number is to partially drain and replace some of your water.

I measured my CYA at 40 and wanted to get to 70. Trouble Free Pool’s Pool Math calculator told me that I needed to add 40 oz of dry stabilizer by volume. I split that into two additions over two weekends. There are multiple ways you can do this. I’m going to detail my experience with using. a few of these methods over two separate weekends.

Method 1: Adding CYA to a Pool By Adding Directly to Skimmer

The first method I found: add the granules directly to the skimmer. This is basically the same way you add the instant (liquid) conditioner. I quickly ruled this method out, for a few reasons. The concentrated conditioner can cause issues with the pool equipment when added directly to the skimmer.

There’s no way of knowing when all granules have dissolved if doing it this way. The granules are going to be pulled through the skimmer to the filter and dissolve there. That makes it impossible to know if the entire dose of conditioner is dissolved inside the filter. That led me to method number two.

Method 2: Using a Skimmer Sock with Chlorine Stabilizer in Skimmer

I poured the granules into a skimmer sock, and put that tied off skimmer sock inside the skimmer basket. This makes it easy to see when all of the granules have dissolved. I actually tried this last weekend, for about an hour. This seems like it would work. However, I very quickly realized that the main issue with doing it this way is that it takes quite some time for the entire dose to dissolve. Some reports I’ve seen say it can take up to 3-4 DAYS for it to dissolve this way, which I wasn’t willing to do.

Since the pump has to run non-stop while it’s dissolving and mixing this stuff, I always do it on the weekend when electricity is cheaper. I’m not OK with running the pump 24/7 during the week, and paying a small fortune to do so.

Method 3: Adding CYA to a Pool by Hanging Chlorine Stabilizer Filled Skimmer Sock in Front of Return

That led me to look around for another option, and find method three. Instead of putting the sock full of granules in the skimmer basket, hang it in the pool in front of a return jet. Make sure it doesn’t touch the walls of the pool.

This worked well, and was much faster to dissolve the conditioner. I did have to give it a bit of a nudge every few hours by pulling the sock out of the water and squeezing it a few times. Using this method, it ended up taking about 36 hours to fully dissolve the entire 20 oz dose of stabilizer. Pretty good, but still I felt like I could find a better way.

Method 4 (OPTIMAL): Hang CYA Skimmer Sock in Water Feature

More research on Trouble Free Pool led me to a single post on the forum that ended up being life changing. Method four: hang the sock full of granules in one of your pool’s waterfalls, if you have any.

adding CYA to a pool by using chlorine stabilizer filled skimmer sock hanging in waterfall

I apologize for only having a night-time picture, but as you can see above, we took one of our aluminum poles (in this case the one we have the skimmer net on), removed the attachment, and laid it across the pool right above the waterfall. I then took a short length of rope and tied it around the skimmer sock. Wrap it around the pole at enough of a length that the sock sits just below the water surface and right in the middle of the spillover waterfall.

Total length of time from start to finish to dose the pool with CYA this way? Less than 12 hours. It’s basically the same as hanging the sock in front of a return jet, but on steroids. The constantly moving water falling over and flowing around the sock full of stabilizer granules dramatically speeds up the dissolution into the water.

Final Analysis

We don’t have to add CYA that often, but from now on I’ll be adding it this way whenever we do. Next time, I’ll try to get a better day-time picture and update this post accordingly. As mentioned above, I’ll also update the post next weekend with my water test results.

If you enjoyed this post, check out some of our other home projects!

UPDATE (8/8/2020): SUCCESS! Full water test numbers after CYA addition are: FC 7, CC 0, pH 7.5, TA 60, CH 950, CYA 70, temp 79.1, salt 3400, CSI -0.07. Perfectly balanced!


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