Today I noticed a "NOT OK" signal from T2 water expansion tank warning level sensor.  I checked the water level in the tank and confirmed that the water level in the tank had indeed dropped.  The water package is currently not connected to the target so it is not possible for this water to enter the beam line.  

My initial suspicion is that the female Hansen fittings are leaking.  If this is the case, the water will be leaking onto the top of the T2 monolith.  The water lines were disconnected from the target on April 12, 2012 and at that time the expansion tank level was checked and confirmed to be full.   Approximately 7 liters of water has been lost since that time.  If the leak rate is steady this equates to 166mL per day.

I will investigate further on Monday morning.  If the cause of the leak is not obvious, a thorough investigation will have to wait until the M20 front end is covered as radiation levels are high around the T2 monolith and cooling package areas.  The current water level in the expansion tank has been recorded, and will be checked again Monday morning in order to see if the level is still decreasing and at what rate.