Fire hydrant break off valve

A fire hydrant break off riser, comprising:

• a riser body comprising:
• a top flange for attachment to a fire hydrant;
• a bottom flange for seating against a water main;
• a downward facing tapered seat;
• pivot axle seats;
• and
• a trigger pocket formed between the top flange of the riser body and a hydrant flange of the fire hydrant;
• break away bolts attaching the fire hydrant to the riser body;
• a valve including an upward facing circumferential valve seat adapted to seat against the tapered seat in the riser body;
• at least one pivot axle pivot axle carried on bosses residing on a bottom surface of the valve, the at least one pivot axle pivotally connecting the valve to the riser body, the at least one pivot axle residing horizontally offset on an axle side of the valve about 57% of a radius R of the valve, and a height H of about one inch below a top surface of the valve;
• and
• a diagonal trigger residing in the trigger pocket at a second end, and pivotally attached to the valve at a first end, the first end opposite to the second end,
• wherein:
• the valve is held in an open position by the diagonal trigger while the second end of the diagonal trigger is restrained by the trigger pocket during normal operation;
• and
• when the fire hydrant breaks away from the riser body, the diagonal trigger is released from the trigger pocket, the valve pivots to a closed position, and the upward facing valve seat is forced against the downward facing tapered seat by water pressure.

A fire hydrant break off riser, comprising:

• a two piece riser body comprising:
• a bottom riser body comprising:
• a first top flange;
• a first bottom flange for seating against the water main;
• a downward facing tapered seat just below the first top flange;
• and
• pivot axle seats;
• a top riser body comprising:
• a second top flange for seating against the fire hydrant;
• a second bottom flange for seating against the first top flange of the bottom riser body;
• a circumferential notch between the second bottom flange and the second top flange creating a weak ring around the top riser body;
• a trigger pocket in an inside wall of the top riser body, above the circumferential notch;
• and
• a break way portion of the top riser body above the circumferential notch;
• the bottom riser body is attached to the fire hydrant by high strength bolts;
• the top riser body is attached to the bottom riser body by the high strength bolts;
• and
• the top riser body is attached to the fire hydrant by the high strength bolts;
• a valve including an upward facing circumferential valve seat adapted to seat against the tapered seat in the bottom riser body;
• at least one pivot axle carried on bosses residing on a bottom surface of the valve, the pivot axles pivotally connecting the valve to the bottom riser body, the at least one pivot axle residing horizontally offset on an axle side of the valve about 57% of a radius R of the valve, and a height H of about one inch below a top surface of the valve;
• and
• a diagonal trigger residing in the trigger pocket at a second end, and pivotally attached to the valve at a first end, the first end opposite to the second end,
• wherein the valve is held in an open position by the diagonal trigger while the second end of the diagonal trigger is restrained by the trigger pocket during normal operation, and the valve pivots to a closed position when the diagonal trigger is released from the trigger pocket when the top riser body breaks at the circumferential notch and the break away portion breaks away, and the upward facing valve seat is forced against the downward facing tapered seat by water pressure.