I'm not so sure about the superchlorination having any real effect on CYA getting dissolved -- I doubt it. If the instructions say to do that, then they probably just want you to be safe in terms of the final Free Chlorine (FC) and Cyanuric Acid (CYA) levels you end up with because starting with something low like an FC of 1-2 ppm and adding 50 ppm CYA will end up with a situation where algae can grow. You wouldn't need to superchlorinate to prevent this, but would need to raise the FC somewhat to around 4 ppm or so.ReDDoG83 said:
Adding CYA to the skimmer, or not
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I would not put shock in the skimmer. Here's why. Whatever the shock may do eventually to the whole pool chemistry, this will be multiplied many times when the shock first passes through the skimmer line into the pump. This is because the amount of water involved is much less than the entire pool, so the shock is much more concentrated in the water that travels to the filter. That is just intuition so far, but here is my experience. We once had an automated chlorinator installed for use with acidic tablets. We had it installed upstream from the pump (big mistake), so that the highly concentrated solution went straight into the pump and then the filter. This was an old filter with brass fittings. A few months later, the handle for the filter controls came off in my hand. The brass innards of the filter were largely gone, dissolved by the acid. Shortly after that, the pump died, the metal parts inside largely gone. The amount of acid in those tablets would not have hurt if it had been dissolved in the entire pool, but it hurt a lot when dissolved in the small amount of water in the pipe. The situation here is the same, because the small amount of water passing through the skimmer may pick up a concentrated dose of whatever you are adding. I admit I am generalizing, but based on my experience, I would be inclined to assume that anything I put into a pipe that is headed for the pump may involve high concentration of chemicals that the pump and filter may not like.
Welcome to TFP! 
This is an over 3 year old thread and no one is saying to add chlorine (which is what I presume you mean by shock) into the skimmer. People are talking about adding Cyanuric Acid (CYA), which is different. It's a weak acid that will get caught into the filter and is added when the pump is running.
What you are talking about are Trichlor tabs and those are about twice as acidic than CYA (four times when accounting for chlorine usage/consumption) and they also release concentrated chlorine. The combination of high chlorine with low pH is a potent combination and is why Trichlor tabs should not be put into the skimmer. It will continue to dissolve slowly when the pump is off and has high chlorine and low pH in its vicinity that can cause damage. They are even a problem in floating chlorinators since they can park themselves near metal in the pool and corrode such metal. And as you point out, inline chlorinators can also be a problem, especially if they do not have check valves preventing the concentrated dissolved product from migrating towards pool equipment or when installed upstream of such equipment.
This is an over 3 year old thread and no one is saying to add chlorine (which is what I presume you mean by shock) into the skimmer. People are talking about adding Cyanuric Acid (CYA), which is different. It's a weak acid that will get caught into the filter and is added when the pump is running.
What you are talking about are Trichlor tabs and those are about twice as acidic than CYA (four times when accounting for chlorine usage/consumption) and they also release concentrated chlorine. The combination of high chlorine with low pH is a potent combination and is why Trichlor tabs should not be put into the skimmer. It will continue to dissolve slowly when the pump is off and has high chlorine and low pH in its vicinity that can cause damage. They are even a problem in floating chlorinators since they can park themselves near metal in the pool and corrode such metal. And as you point out, inline chlorinators can also be a problem, especially if they do not have check valves preventing the concentrated dissolved product from migrating towards pool equipment or when installed upstream of such equipment.
sunrise
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I am using Trichlor in granulated form. How to apply that and preventing putting it into the skimmer? Throwing it into the pool water already softened and even dissolved my grout between the floor tiles. I know there are floating dispensers for tablets but could not find anything for granular Trichlor. I tried a floating kitchen strainer (tips over occasionally and then the stuff ends up again on the floor eating my grout), a sock which is also eaten away by the Trichlor. Any recommendations? Installing a dispenser in the return after the filter made for liquid chlorine or for Tablets and putting a sock or other filter in there? What do the others use?
Is it possible to dissolve Trichlor granules first and then the solution still works when poured into the pool water or is it doing it´s job only in the dissolving jug?
Is it possible to dissolve Trichlor granules first and then the solution still works when poured into the pool water or is it doing it´s job only in the dissolving jug?
sunrise
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Not possible here. They have only Gallon containers and do neither state the percentage nor the production or expiration date.
