Drain Required with Each Pipe Drop Below Beam?

4/27/2021

In one of my jobs I have a fire sprinkler contractor who claims something that seemed strange to me. I have searched online but didn’t find the code section to show him.

He has laid out his Victaulic piping for two open space office under the beams and when I asked him why he didn't run them up high through the joists and instead only route the pipes underneath the beam where they have to, he responded that for each time that a pipe goes up and down, it requires a drain.

My question is in a wet sprinkler system in an office, do we need to provide drains for every time that a pipe is going few inches down and then back up? Since the entire system is wet and under pressure, are these drains necessary per any code? Whether we do require that or not, can anyone refer me to the pertaining code section?

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17 Comments

Jeremy Fowler

4/27/2021 08:14:01 am

Refer to 2016 NFPA 13 section 8.16.2.5 Auxiliary Drains. It pertains to how much water is trapped as to what the drain requirements are.

Bruce Seiler

4/27/2021 08:14:58 am

NFPA 13 (2019 Edition) Section 16.10.5.2 talks about auxiliary drains for Wet Pipe Systems. "Where the capacity of isolated trapped sections of pipe is 50 gal or more, the auxiliary drain shall consist of a valve not smaller than 1in. piped to an accessible location." If you are running a system high and dropping below beams, the likely hood of trapped sections containing more than 50 gallons (200 L)might be higher, although water would find its level and still drain where it could. If that trapped section of pipe is less than 5 gal ( 20 L), you merely need a plugged fitting or in the case of a Victaulic Grooved System, a grooved coupling. The reason for this requirement is to drain down the system properly when working on the system. If you don't have a properly drained/valved system, it will take a lot of 50 gallon drums to drain the system or a long hose running through the office building.

wnuk09

4/27/2021 08:19:31 am

I've come across this once before as well. In my opinion the contractor is correct in saying you need a drain where there's any location that water could become trapped. During some maintenance procedures, the entire wet pipe system needs to be drained for inspection. 2016 NFPA-13 8.16.2.5 addresses when an auxiliary drain is required.

Franck

4/27/2021 08:24:07 am

The purpose for properly draining all the system (even for wet system) is to limit possible corrosion issues (as well as to mimit water damages if you need to dismantle the pipes after drainage).

When you drain your entire system, all the pockets of water will be "fuel" for corrosion, and the longer you keep your system out of water, the more problems you will have.

Proper indication have been provided above on how to provide drain capacities depening on the trapped volume of water.

Glenn Berger

4/27/2021 08:26:27 am

When I am inspecting sprinkler system installations, one of the easiest punchlist items to spot is the omission of low point drains. No one has been able to prove that a drain is not required due to the small amount of water trapped.

It is recommended to put it in during the initial installation then trying to retrofit it during the inspection and test operations.

Franck

4/27/2021 08:29:41 am

Another explabation, for not going up and down, may also be related to the equivalent length for friction loss calcuation. If you go up and down and up again for each neam, this means 4 x 90° elbows, and dependning on the size of your pipe, this couild lead to high additionnaly friction losses in your system (as your feed main is used on its entire length with these up and down, not only at the most remote area).

Jesse

4/27/2021 08:31:10 am

Look at 2016 NFPA 13 Ch. 8.16.2.5.2 - this directs the size of the drain needed based upon the amount of trapped water.

James

4/27/2021 08:36:15 am

I see some architects/consultants request this kind of thing from time to time - just drop down below each beam and come back up.

It's easier said than done - not only is it a lot of fittings and a lot of friction loss, but there's far more labor cost to it as well. If pipe through the open-web joists is really desired, then the consultant should consider coordinating holes in the solid beams for a straight-run of branch lines. It would require significantly more coordination on the consultant's part, but it'd be cleaner and pipe would still be high. A good value-ad for being a consultant on the project.

Jon Sullivan

4/27/2021 09:34:21 am

Great advice. If you want to be on the structural engineer's good side, typically these penetrations should be in the middle 1/3 of the beam height and span.

It's a lot easier to have these fabricated in the steel shop rather than on site.

Casey Milhorn

4/27/2021 09:40:30 am

Agreed. We used to fight going "into the beams" but it's a great way to make sure you have the space all to yourself (mostly) and it's easier to get someone to move their stuff when you are in a designated spot and elevation. Might mean a few more couplings and little slower install, but I'll take the safe route over the unknown every time. But NEVER agree to torch the holes as a sprinkler sub. Way too much exposure in that AND sizes and locations must be approved by the structural engineer ahead of time. Also don't forget the seismic clearances required if on a seismic job. It could get very expensive using (2) flexible couplings at every hole.

Casey Milhorn

4/27/2021 08:53:55 am

Without looking it up, the old rule has been 5 gallons or less can be drained through a sprinkler in the pendent position or a plug or cap. Over 5 gallons to 50 gallons, a plugged valve of some sort is required. More than 50 gallons and a valve should be provided piped to an accessible location (typically outside, can wash, mop sink, near an outside door, etc). Those are my suggestions, not NFPAs. I don't think it goes into detail what an accessible location is. BUT, I would agree with the contractor that it is not a good practice to trap water without some very good reasons behind it. You are giving the building owner future headaches, corrosion issues, etc... that WILL translate into additional cost for the owner at some point down the road.

CJ Bonczyk

4/27/2021 09:18:03 am

Casey, completely agree with you and everyone else comments regarding this question. To answer your comment on what NFPA considers and accessible location... NFPA 13 2019 Handbook states accessible is the valve would be located approximately 7' A.F.F. to which a hose can be connected to discharge the water in an acceptable manner.

Jessica Lutz

4/27/2021 09:31:53 am

@CaseyMilhorn - THIS!!!!
Drainage consideration has come to the forefront in sprinkler design as of late. (The most annoying part of sprinkler systems...the necessary afterthought. I mean, for a long time the fitters would just take care of this in the field as they went along...not anymore.)
And I 100% agree with you on your guidelines.
Yep, and the "accessibility" definition angle...I've heard many interpretations.
I'd like to add, the larger capacity drains' termination points should be verified with all local building codes, as always.
Out in LA, they want them piped indirectly to sanitary hub drains.
In other surrounding counties, it's ok to pipe them to mopsinks, or floor sinks.

I could write a book...

Jon Sullivan

4/27/2021 01:39:13 pm

What plumbing code do they follow in LA? IPC allows any floor drain, mop sink, hub drain, or standpipe as an indirect waste receptor.

Jessica Lutz

4/27/2021 01:57:51 pm

@JonSullivan
They follow the CA Plbg Code, based on the UPC.
Sometimes, we're at the mercy of the inspectors also.
To avoid the argument altogether, I avoid trapping over 50 gal like the plague.

John Lane

4/27/2021 09:33:10 am

NFPA 13 (2016 Ed) Section 8.16.2.5.2.3 Covers everything Casey just said.

Jeff Garrison link

4/30/2021 09:18:05 am

We had CPVC in a residential highrise - 1.25" main where we
45'd maybe an inch under a few obstuctions (trapped water was about 8 oz.) and the AHJ made us put in a legal drain for each.
(cut-in and glued a tee w/ threaded plug outlet.)

Drain Required with Each Pipe Drop Below Beam?

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