How long does it take liquid chlorine to degrade in strength? I bought some from my local Ace Hardware store and when I poured it in my pool is was clear not yellow like previous chlorine I have bought. Three hours after I added it I checked my chlorine and it did not change. My math indicated that it should have moved 3 PPM. There is no a doubt in my mind that the chlorine that I bought is the remnants from the end of last season could it have degraded to zero strength?