I USE THE PP FROM WALMART, I'VE USED THE SAME BATCH FOR OVER A YEAR OR SO, I KEEP IT IN AN OLD ICE CONTAINER SITTING ON MY BASEMENT FLOOR. IT GETS WEAKER AFTER A WHILE, I DO KEEP A COVER ON IT, IT WILL EVAPORATE OVER TIME. I ALSO JUST FOUND OUT THE HARD WAY THAT WESLEY'S BLEACH WHITE WILL EAT THROUGH A CLOROX BLEECH BOTTLE