Richard
Its very sunny outside today in jersey so hopefully the Fc will burn off, I tested the water for ammonia this morning and its totaly clear..i am still getting a very high FC and PH level and i presume there is nothing to do but wait it out untill it all burns off. do you think that the high ph for the next few days can damage the plaster finish?
I use a nature 2 cartridge during the pool season to have low chlorine in the water. (i havent installed it yet becouse my water was not balanced). what is your feeling about the product? is it safe to keep the fc at 1% as they suggest?
26 gallons of 12.5% chlorinating liquid in 48,000 gallons would raise the FC by 67.7 ppm which is very high (yes, you added too much -- the 10 ppm FC at a time would have been better). You are lucky your pool didn't get cloudy and/or produce scale since the pH would have shot way up to around 8.6 from the chlorine and the saturation index would have been over +0.9. However, within the hour, the chlorine would have oxidized the ammonia and brought back down the pH a little. If I assume that the 4 ppm ammonia-nitrogen was correct and that this consumed about 30 ppm FC, then the pH would have dropped to around 8.4 and you'd have about 38 ppm FC left over and the saturation index would be +0.8. Still pretty high. So yes, let the sun burn that off, which it should do somewhat quickly since the CYA level isn't really high. You might have the FC drop by a third in one day -- maybe almost half if you are in a very intense sunny area (though we're not in June yet). The pH will drop as the chlorine gets broken down from the sun and should get back to around 7.5 to 7.8 depending on what FC level you let it get to.
In the future, use The Pool Calculator to figure out the dosing of chemicals for your pool.
Richard