I worked at a  NTNC-Non-community non-transient water system for 3 years. water was used 24 hours a day 7 days a week.  I am now work at a Non-community non-transient water system. From 3:00 P.M. until 5:00 A.M the building is empty and no water usage. when I take my free chlorine reading the next day it takes for ever to get a reading at or above 0.2 any tricks to this type of system?

yes we use the hach dpd.

I go to the nearest sink turn the water on ( put a sign on faucet  water test in progress don’t turn off) I then go to the furthest sink  turn it on (put another sign on it) go to next building and do the same. I then return to the first sink and take a reading.  It takes about 15 to 20 min before I return and take a reading.  I am also questioning the Hach meter I can take the same sample and get two different reading. The reading are not even close to values.

I zero the meter each time with chlorine free water.

I agree running the water for 20 minutes is a waste. Without running the water we show no free chlorine and you need to have a residual at two sample points. After looking in to this deeper it was discovered the water in the holding tank was not being chlorinated the chlorine injector line was hooked up after the tank. So the water was being chlorinated as it was used.