This question is being answered just in case something like this happens during a weekend swim party. We have all heard the horror stories of fecal matter contaminating pools with cryptosporidium. Cryptosporidium is a nasty little bug that can cause a bad stomach and intestinal illness. If this does happen everyone should get out of the pool. The fecal matter should be scooped out and filter ran continuously. The pool should be safe to re-enter 1 hr. later. We use 100% pure chlorine gas and the chlorine level should be sufficient to kill any bacteria left in the water. If you want some peace of mind then you could shock the pool with 2 chlorine shock packs available at any local retailer and swim 1 hr. later.