So in my last two playthroughs I've noticed that the dupes will sometimes endlessly deliver contaminated water to anything that needs water. However since the machines they deliver it to wont accept the water they just end up deleting it and repeating the cycle. This normally happens when I either have no pure water available, or I have very little pure water. Specifically, the dupes will deliver endlessly to the 'Algae Terrariums' and 'Microbe Mushers'.
-Run out of pure water -have contaminated water available -let duplicates deliver water to machines.