Chlorine tablets in skimmer help

[kristalou]

I am wondering what the rule is for leaving 3lb chlorine tablets in the skimmer. Does the filter have to run constantly? I left one in my skimmer while I was gone for the weekend (not running the filter) and I came back to what looks like a stained vinyl cover. I have a 15 X48 vinyl pool. Is there an easier way to chlorinate without leaving a tablet in a skimmer? Thanks

[chem geek]

I think you mean 3" not 3 pound, didn't you? The 3" Trichlor tabs/pucks are usually around 8 ounces weight (half a pound). And these should NOT be put into the skimmer unless the pump is always running and even then it's risky if the power goes out. Trichlor is VERY acidic. Even in a floating feeder they are dangerous unless you park the feeder away from a pool edge.

[kristalou]

Is there an easier way to chlorinate without using the tablets then?

[chem geek]

Unfortunately, Trichlor tabs are the most convenient form of chlorine since they slowly dissolve and can be used in floating feeders. A saltwater chlorine generator (SWG) is even more convenient.

There are some slow-dissolving Cal-Hypo pucks but they may fall apart near the end and leave a residue (at least that's the way they used to be -- maybe new ones are better now). For every 1 ppm FC they add 0.7 ppm Calcium Hardness (CH), but in percentage terms that's not too bad since CH is usually around 300 ppm.

The more pure forms of chlorine that do not increase CYA nor CH are unfortunately not convenient in terms of slow delivery. Bleach or chlorinating liquid (both are sodium hypochlorite) must be added every day (usually) unless one has a pool cover. Lithium hypochlorite is similar in that respect.

So when using Trichlor you either need to use a weekly PolyQuat 60 algaecide to prevent algae (and then not worry too much about the CYA level) or you need to do partial drain/refill or more frequent backwashing to dilute the water to keep the CYA level lower or you need to maintain proportionately higher FC levels (target 11.5% of CYA level with absolute minimum of 7.5% of CYA level).

Richard