What is up with the CYA in a sock?

[Nightmare]

So I put about 32 oz of stabilizer (CYA) in a sock yesterday. I put the sock into the skimmer basket furthest from the pump (because everything said to add it slowly). I go out there this morning (pump running all night) and I still have a full, wet sock of white powder. If I squeeze the sock it will leak out white liquid.

Did I pick a sock with too much material? Or does it take a LONG time to leach out the CYA?

 

[mynewpool]

You should have the sock in front of a return.

 

[Ohm_Boy]

It takes a LONG time to fully dissolve CYA.
That is actually the reason for using a sock in the first place. Folks used to just add CYA to the skimmer, and that works well, but since it can literally take weeks to fully dissolve, it hangs around in the filter. If one were to backwash their filter during that time, the undissolved CYA would be unknowingly lost. If you know that, and can manage not to backwash your filter for a couple of weeks, you can forego the sock.

 

[Melt In The Sun]

patience patience... :-D

 

[Nightmare]

I moved the sock to the closer skimmer basket. It pulls more water.

I have a Jandy CL580 Cartridge Filter, so I don't need to backwash. I cleaned the filter for the first time a week ago.

The instructions from BioGuard said to:

"Broadcast directly into the pool, scattering over the surface. Brush up any undissolved product"
or
"For pools with plastic piping, Stabilizer 100 can be added VERY SLOWLY through the skimmer with the pump running. Circulate continuously for at least 24 hours. DO NOT BACKWASH FOR 48 HOURS IF ADDED THROUGH SKIMMER"

 

[Melt In The Sun]

Since you have a cartridge filter, I'd say just dump it down the skimmer and let it dissolve in there.

 

[Ohm_Boy]

Broadcasting and vacuuming is pretty much just adding it to the filter, as CYA is very slow to dissolve. Just be aware that with any method of application, it can take a fair bit of time before you see the full CYA reading on tests, again, due to long dissolve times. At least if it is in a sock hanging in the pool or skimmer, you will be readily aware that there is undissolved stock, and you will know why the readings are still below the expected levels.

Also, once you add it, you should chlorinate as if you had the fully dissolved amount of stabilizer in the water, regardless of how much has dissolved.

 

[chem geek]

I've used an old T-shirt that I covered over the skimmer basket, sort of like a skimmer sock, and then added the CYA to it. After overnight running the pump, most of the CYA is dissolved and within one day (24 hours) it is fully dissolved. That's for adding around 20 ppm CYA to a 16,000 gallon pool. Adding more CYA will likely take longer.

I suspect that the sock is too thick to have enough water flow through it. The use of a T-shirt, skimmer sock, or maybe even panty hose would probably make it go faster. Of course this is partly because some very small pieces will slip through, but it will give you a greater sense of accomplishment! Actually, I've measured the CYA after it looked like it was dissolved and it usually measures at least 3/4ths of the added CYA amount so most of it apparently does get fully dissolved.

The problem with having it get caught in the filter is that the flow rate there per surface area is VERY slow which is why it can take up to a week to dissolve. It may be dispersed, but the water flow rate is slow. In my pool at 48 GPM through my 340 square foot area cartridge filter this would be around 0.2 inches per minute water velocity through the filter. Yes, you read that right -- that's what an oversized cartridge filter will give you. In the skimmer basket given two floor drains and one skimmer, I figure around 10-15 GPM through the skimmer which with a 6" diameter at its base would be about 7-10 feet per minute water velocity, though of course when there's a lot of CYA there the flow is very restricted.

 

[JamesW]

When putting cyanuric acid in a cloth, most of the water flow will go around the bundle of cyanuric acid and so there will be very little water flow across the cyanuric acid. I have found that cyanuric acid dissolves much faster in a filter than when using a sock, towel or other cloth.

I poured some cyanuric acid into a skimmer and the cyanuric acid went into the filter. Since it is an acid, I was concerned about the pH dropping too much and causing damage to the heater, so I measured the pH of the water from a return and the pH was off the scale too low.

I also measured the TA, but it was not low due to the cyanuric acid being a weak acid and forming cyanurates. I quickly backwashed into a knee high stocking to get rid of the cyanuric acid and put the cyanuric acid in a towel to allow it to dissolve slower.

When testing the pH using a cloth, there was no noticeable pH drop.

 

[Flotsam]

I used an old "boot sock" - one that I used when hiking (its "mate" developed a hole in the toe so my wife pronounced the pair "dead") ... but I digress ...

I initially hung the CYA laden sock near the deep end ladder - it was still in the circulation pattern and "out of the way", but I noticed it wasn't dissolving as quickly as I wanted (water doesn't flow out of the faucet fast enough either) - so I moved it to the skimmer basket. It took about 2 days to dissolve.

My point is - the boot sock is a very heavy weave - yet very porus - so placing it into the skimmer with the additional flow seemed to dissolve the CYA much quicker than just hanging it off the ladder. None of the particles get hung up in the filter when pouring it straight into the skimmer and they don't settle to the bottom if broadcast dispersion is used.

I'm still kinda green with the BBB method and I'm learning every day from all the great posts here - just sharing my new observations. HTH !!!

Mike

 

[chem geek]

Flotsam, thanks for sharing your observations.

When putting cyanuric acid in a cloth, most of the water flow will go around the bundle of cyanuric acid and so there will be very little water flow across the cyanuric acid. I have found that cyanuric acid dissolves much faster in a filter than when using a sock, towel or other cloth.

That may be your experience, but for me the CYA was mostly dissolved through the skimmer T-shirt method overnight with the pump running continuously and after 24 hours most of it was measurable in the water. I've done this pretty much every year for at least 5 years when getting the pool ready in spring. I have never tried it directly added to the filter (by adding to the skimmer without obstruction) but others have reported doing this and not getting CYA to show a substantial increase for a few days or even longer. Perhaps it depends on the filter and flow rate through that filter -- my cartridge example would be somewhat extreme compared to a sand or DE filter. Sand filters have different effective filter areas, but range in the 1.5-3.5 square foot where obviously the water velocity would be far higher than the 340 square feet of the cartridge filter example I gave -- over 100 times higher water velocity (flow rate per area). That probably explains the difference in experiences (unless you have an oversized cartridge filter like I do).

So the recommendation for adding CYA through the skimmer to get caught in the filter might make sense for a sand filter, but not for a cartridge filter, especially if oversized.