Where to Run a Second Floor FP Drain?

9/14/2021

We have a floor control valve and 2-inch drain pipe on a multi-story building.

Where should I drain this?

If I drain directly to a floor drain in a toilet room, I'm not confident that the floor drain can accept the flow.

Can I connect it to an HDPE pipe and drain it underground to a gully trap?

I fear connecting it to anything under tile as the drain lines are PVC and may not afford the pressure.

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8 Comments

Alex

9/14/2021 07:12:45 am

Hi Anonymous,

I’m guessing you don’t have a main drain then? If you do, problem solved! If not, since you’re only on the second floor, is it possible to core a drain within the stairwell and discharge outside?

In my past experience, you do not want to drain into a floor drain as it may not accept the flow as you mentioned. Even if the floor drain is sized sufficiently, getting the water down the drain is the issue.

NFPA 13 (2016) 8.16.2.6.1 states that “direct interconnections shall not be made between sprinkler drains and sewers”. A gully trap is typically for odors and not backflow. I don’t believe this would be an acceptable design to protect the system. The code further reads that if you wish to pipe the discharge to the sewer, the drain should run to a sump, which in turn is discharged by gravity/pump to the sewer.

Best of luck with your design!
Alex

Jon Sullivan

9/14/2021 08:08:58 am

Hi Alex -

IPC does not specifically require a sump and pump in this situation. It does require a disconnect between the systems by a means of an air gap/break. This is typical for for wastes of this type. See IPC 2021 802.1.5

Dan Wilder

9/14/2021 07:26:22 am

Follow your feed main routing with the drain unless you have remote test location requirements, then I typically find a mechanical chase or roof drain box out as these are typically straight shots to the ground level.

You also stated multi-story but did not specify what edition you were working from. 13-16' 8.16.2.4.8 states that a "..common drain shall be one pipe size larger downstream of each size drain connection tying into it". You may need to increase the drain size to 2½" for the common (gang) drain.

matt

9/14/2021 08:09:27 am

I agree with Alex and Dan. Best bet is to run it directly outside or tie into another sprinkler drain.

Even if the plumbing could handle it in theory - we have seen MANY cases where a floor drain or mop sink is allowed to get a little bit clogged or drain slowly. It may not be a problem when you dump out a mop bucket, but you will find the slow drain very quickly when a technician opens the main drain.

Jon Sullivan

9/14/2021 08:19:13 am

If the plumbing engineer/designer has flow rate they can size the drains. We can work backwards from the drain (or RPZ) flow rate to establish a pipe size using 1 gpm is equivalent to 2 DFU and use an estimated ponding depth over the drain to arrive a required grate free area.

Glenn Berger

9/14/2021 08:25:19 am

Route drain to exterior if possible. Do not route to toilet of regular floor drain.

Manny Rios

9/14/2021 09:37:53 am

In our jurisdiction, these drains are to be installed with the flow directly to the exterior of the buildings.

The floor drains are not sized to accommodate the flow and through trial/error up flooding said area.

As already stated, if possible connect to other fp system drains or independently to the exterior of the buildings.

Good luck on your design.

Jessica Lutz

9/14/2021 10:26:20 am

Consult your local AHJ requirements...this can vary by state, city, county.

Some areas allow indirect drainage outside the building, some require indirect to sanitary inside the building.

If there's a plumber onboard, ask them.

The regular toilet room floor drain usually won't cut it.

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Where to Run a Second Floor FP Drain?

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