Replace Recalled Sprinkler w/ Different K-Factor?

12/23/2020

I recently acquired a project where I'm replacing all sprinkler in a residential home. Apparently the original sprinkler heads were the OMEGA that were recalled some years ago on.

These specific heads had a K=factor of 3.9 and although I have found only one direct replacement with the 3.9 K=factor, they are not cheap!

My question is what would be an alternative replacement to these k-3.9 Omegas, and would replacements need to be the same k-factor?

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8 Comments

James Phifer

12/23/2020 09:28:05 am

Found this in NFPA 13, 2016 edition. Hope it helps.

11.3.1.4.1 Where replacing residential sprinklers manufactured
prior to 2003 that are no longer available from the
manufacturer and that are installed using a design density less
than 0.05 gpm/ft2 (2.04 mm/min), a residential sprinkler
with an equivalent K-factor (± 5 percent) shall be permitted to
be used provided the currently listed coverage area for the
replacement sprinkler is not exceeded.

Kelsey

12/23/2020 10:33:00 am

Came here to say this as well. The 5% has been close enough for me in a few situations but not all, and then more investigation is needed. Good luck to you!

Dave L.

12/23/2020 10:39:00 am

I'm confident a current replacement can be found with similar or better performance characteristics (and maybe similar takeout), and they should be replaced. But respectfully, are you certain it is an Omega with 3.9K? I don't recall (no pun) a 3.9K recalled Omega sprinkler.

12/23/2020 09:31:40 am

I've run into a similar situation. You either need to match the fire sprinkler characteristics or survey the existing system and run hydraulic calculations to make sure the calcs work with a different k-factor. It could definitely be worth some design time to save the cost of expensive sprinklers if you're replacing a large quantity of sprinklers.

Casey Milhorn

12/23/2020 09:43:11 am

Of course the correct thing to do if you using a different K factor is to recalculate the system. The issue will be the possible can of worms you are about to open by doing that. You don't know what it was originally designed to at the time (or maybe you do) and water supply could have deteriorated over time. You might be left with a system that doesn't work even with the original K factor heads. The K3.9s were during a time when some of the manufacturers were in a race to have a K factor for every different spacing and scenario. NFPA reigned them all in with standardized K factors thankfully. Even with the same K factor head, there is still a chance that the design parameters have changed for that particular head. All that being said, if the AHJ is reasonable, there should be no reason to use a little common sense and throw a 4.2K in there as a cost effective replacement. It should throw just as far, if not farther with almost the same pressure as the 3.9K. That's my two cents.

Franck

12/23/2020 09:55:38 am

I can’t answer from a regulation’s standpoint (not living in the US), but the answer from NK is technically correct.
If you replace with same k-factor (+/- 5% as indicated by James), you have the advantage that you don’t need to prove the efficiency of the system as it is the same design.
If you change the k-factor, you need to make new hydraulic calculations to proves that it works with your existing water supply. Normally, with greater k-factor you end up with a larger flow demand. The final pressure demand is then dependent on the pipe layout and should normally be lower when friction losses are limited, but could also be higher...
The advantages of having a different k-factor, in addition to the price in your case, is also to limit possible clogging of the orifice. The smaller the orifice and the older the pipes (if steel made) the more chances of obstructions.
For storage facilities (and larger design), the other advantage of larger orifices is to produce larger droplets that can better penetrate the heat plume. Thus the recommended practice from NFPA 13 to have larger orifices for higher densities with storage occupancies (8.0 or 11.2 rather than 5.6).

Franck

12/23/2020 10:01:07 am

Information from Casey are also good technical advices.
Of course, if you have the initial design parameters with the hydraulic demand at that time, it does make sense to ensure that your current water supply is still sufficient.
But this should apply in all cases, not only because you make a renovation.
If your water supply is not strong enough anymore, you would certainly have an issue.

Mark Fessenden

1/5/2021 12:26:04 pm

The Central R-1M was a 3.9 K residential pendent sprinkler. It's listed flow ratings ranged from 9 gpm at 12'x12' & 14'x14', 14 gpm at 16'x16' & 18'x18', and 16 gpm at 20'x20'. The face of fitting to finished ceiling distance was 1-1/16" Max to 7/16" min. Current 3.0 K res pendents have a reduced water demand at spacings 16'x16' or less. I am not aware of a currently listed residential sprinkler with a 3.0 K that is listed for 18'x18' or 20'x20'. If your original R-1M's are spaced at 18'x18' or 20'x20', you would need to reevaluate your calculations. If your spacing is 16'x16' or less, you can simply drop in the current 3.0 K. You will likely need an extension piece to make up the difference in take out.

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Replace Recalled Sprinkler w/ Different K-Factor?

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