The Product Manager is out of the office. I read the literature. The flow sensor feature gives alarms with high/low flow readings. The flow rates are 'learned' during the installation process. The controller operates each station for a couple minutes to let flow settle down and then records the 'standard' flow. There is a default high and low flow threshold which is adjustable. The default high and low flow thresholds are different and can be independently changed. In other words, it is not a set percent plus/minus for high and low. It could 110% as the high flow threshold and 60% for low flow threshold. A zone can 'by-pass' the flow sensor function. In other words, if there is a zone where a high/low alarm is not desired, it can be disabled for that zone. If I learn more after talking to the Product Manager, I will give an update.