Fire Hydrants Are Designed To Shear

Sheared fire hydrant

We came across this scene while walking to lunch the other day. It was clearly a standpipe missing its fire hydrant with a bit of water slowly weeping out. The missing fire hydrant wasn’t too surprising; people hit those all the time creating a giant geyser. What was weird was the little worms of silicone sticking out of the bolt flange. We realized then that the 3/4″ fire hydrant bolts are designed to shear off when hit. I suspect this is so that the impact doesn’t damage the vertical pipe which would require excavation to replace. It might also reduce the force of the accident better than hitting a truly fixed object. It looks like this flange is too low and will have to be dug out before they can put a a new hydrant in.


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