Hope your week in fire protection is going well.
Standpipes within stairs can be an important item to coordinate with the project architect, as the fix for the lack of coordination can be extremely difficult to accomplish in the field. This week I'm breaking down an enlarged floor plan detail for a standpipe hose connection within a stairwell.
Avoiding the Egress Path
The image above shows the clear span that's required to maintain clearance. How do you know the radius of this line? Just take the width of the stair, set the center of your arc to the edge of the stair, and draw your arc from one end of the stair to the other. This is an extension of the required egress of the stair to turn on the landing and move the other direction.
Is it possible and allowed to locate small parts of the hose connection within this clear span? There could be a basis for it.
In design I try to avoid any controversy by locating both the standpipe and those valve entirely outside of this egress path. Doing so may require a little extra space on the landing, but it is far better than finding out after the stair is constructed that you're short on space.
A traditional new-construction stair will likely have support for the stairwell landing incorporated into the stair enclosure, or contain a beam across the landing where the landing meets the beginning of the stairs if it's a concrete stair. These new builds don't present too much of a challenge to coordinate with structure.
However, for retrofits or stairs that do not simply jog back and forth, beware of beams that could run where you'd like to locate the standpipe connections. Core drilling a 4-inch to 10-inch hole through a concrete beam will not make you good friends with the structural engineer.
The hose connection is required to have 3-inches of clearance on all sides of the handle. (NFPA 14 2013-19 4.7.5)
It's not enough to just stick your hand and start turning the valve, we have to remember that it's the firefighter's thermally insulated and rigid gloves that must turn the hose valve while the building is literally on fire. Giving 3-inches of clearance just feels like a minimally-nice gesture to thank your local first responder.
Lastly, don't forget about the drain riser.
If the standpipe includes pressure-reducing valves, these valves require testing and it's required to have a way to connect directly to an oversized drain riser that can handle the testing. This can be done with capped outlets on the drain riser that can accept a hose connection for testing.
NFPA 14 provides guidance on sizing the drain riser in this scenario: 3-inch drain riser for 2-1/2-inch pressure reducing devices, a 2-inch riser for 1-1/2-inch pressure reducing devices, or sized large enough to handle the full flow from the largest pressure reducing device. (NFPA 14 20037.12, 2007-19 7.11.1)
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Joseph Meyer, PE, owns/operates his own Fire Protection Engineering practice in St. Louis, Missouri. See bio on About page.