Before you start using them you will need to find out how much they are really dosing per minute. I think you are supposed to let it run for 10 minutes and then measure the output and divide by 10. Mine doses 1.9ml per minute. After you determine that, it is as easy as doing some simple math to figure out how long to run the timer. So if your doser does put out 1.1ml per minute and you want to does 100 ml per day then divide 1.1 by 100 and you get 90.9 minutes.