(Update 7:44PM PST) TEPCO's morning presser over. It seems the quality of the reporters has gone down while I wasn't watching...
(Update) The [AREVA] system uses 6 different chemicals. There are at least 6 other similar joints, which will need to be checked.
(Update) Watching TEPCO's press conference, ongoing. The operator was a worker from TEPCO affiliate company. He was doing the remote monitoring and noticed the leak. About 50 liters of chemical leaked before the system was stopped.
Bad quality screen capture of the joint that leaked (not uploaded yet as press handout):
(UPDATE @7:22PM Pacific Standard Time) The leak is at the pipe joint. A rather vigorous leak. Cause yet unknown.
It happened before the earthquake.
Tweet from a journalist who regularly attends TEPCO's press conference:
According to the email from TEPCO, at 4:53AM today, at the coprecipitation and coagulation unit of the contaminated water treatment system at Fukushima I Nuclear Power Plant, a leak was found at the line that feeds the chemicals. The operation of the unit was stopped.