#TBT from the NFPA Archives:  Break in the ten inch high pressure water main, San Francisco, 1913

Blog Post created by maryelizabethwoodruff Employee on Aug 4, 2016


From the NFPA Quarterly, v. 7, no. 1

“A contractor was clearing out and excavating an old vacant lot which had not been used since the fire of 1906.  The street was held back by an old brick retaining wall.  When he began excavating below this wall it caved in, allowing all the earth and pavement from the area wall back to the street care lines to fall into this excavation.  This left approximately 150 feet of 10 inch high pressure main suspended in the air and it naturally broke of its own weight.


The present practice is to cut off by means of gates at the corners, any block in which similar work is being done.  As the high pressure is a gridiron system, with gates at each corner, any block may be cut out without affecting the remainder of the system.


When this break occurred the large amount of water rushing out under a static pressure of 180 pounds carried away all other piping and conduits on that side of the street.


Approximately fifteen minutes elapsed form the time the break occurred to the time the water was shut off.  When it is considered this was the first accident the system has had, the work of the Fire Department appears to have been very credible.”