Two other inmates have transported to an outside hospital for treament. Those inmates have not yet received an official diagnosis.
Sky 7 HD showed inmates Friday lining up outside to use portable toilets because the water was turned off.
The prison is trying to control the outbreak. Prison authorities turned off the plumbing and brought in portable toilets, creating long lines in places.
San Quentin Prison Lt. Sam Robinson ordered 100 portable toilets for 2,000 inmates who are actually using the facilities. That's one for every 200 men. There are a total of 3,742 inmates at San Quentin.
San Quentin confirmed the outbreak Thursday after testing one inmate sent out for treatment.
The prison says 30 inmates have severe, flu-like symptoms which include headaches, chills, fever, muscle pain, shortness of breath and nausea.
"This is across the entire prison," Robinson said.
The source of the outbreak is unknown, but Legionnaires'comes through bacteria in water. The Marin Health Department is investigating the outbreak.
For inmates, that means no showering, no inmate transfers to or from other prisons and no visitors, possibly through the weekend.
More correctional officers will be on duty to escort inmates to the portable toilets.
For now, inmates are drinking bottled water. The prison has ordered tanks filled with 7,000 gallons for other uses.
Karen Parodi works inside as a supervisor in the food preparation unit.
"Well, the way I look at this, things happen and you got to take care of yourself. If you are health conscious, you do what they ask you do to," Parodi said.
Inmates are advised to not drink or even touch the water.
Officials are not sure how long testing will take. All volunteer groups are not being allowed onto the grounds until the facility has been cleared.
According to the Centers for Disease Control and Prevention, symptoms for Legionnaires' disease resemble pneumonia and can include cough shortness of breath, high fever, muscle aches and headaches. The CDC says people get sick by breathing in mist or vapor containing the bacteria. Legionnaires is not spread person-to-person and is effectively treated with antibiotics.
While Legionnaires' disease doesn't seem very common, there have been several cases this year alone including outbreaks at a New York Hotel and an Illinois veterans' home. Two deaths are also blamed on the illness in Canada.