How to Fix Too Much Shock in a Swimming Pool
Purchase a swimming pool chlorine water test kit that specifically measures for free chlorine in the pool. A pool with too much shock will have high levels of free chlorine. Follow the manufacturer's instructions to read the results of the test kit, since different kits vary.
Evacuate the pool. No swimmers should be in the pool when you treat for too much chlorine.
Turn on pool filtration pumps. Add one-half ounce of sodium thiosulfate granules per 1,000 gallons of swimming pool water directly into the center of the pool. Allow swimming pool water to circulate with the sodium thiosulfate granules in the water for about 30 minutes.
Turn off pool filtration pumps and unplug from the electrical source. Test the swimming pool water for free chlorine levels. If levels are still too high, repeat Step 3.
Remove pool filters when optimum free chlorine levels are reached. Replace with new pool filters.
Plug back in and turn pool filtration pumps back on. Test chlorine levels weekly. Carefully measure and follow manufacturer's instructions when adding additional chlorine to the swimming pool to prevent future episodes of too much shock in swimming pool water.