A Check Valve Equivalent to BFP for Antifreeze?

10/19/2023

Our State Department of Natural Resources requires a double check on all water based sprinkler systems and an RPZ backflow when additives such as foam or antifreeze are used.

The rule is for containment. Meaning that the first available connection requires the backflow preventer.

With the details shown in NFPA 13 there are examples of check valves with a drilled clapper as well as an appropriate backflow preventer in the examples shown appear to be isolation devices.

NFPA 13 FIGURE 8.6.3.3 shows a backflow preventer and includes an expansion tank.

If the entire building is protected by an RPZ the water department is satisfied.

When approaching the antifreeze pipe arrangement FIGURE 8.6.3.3 wouldn’t a swing check without a drilled hole be equal to the backflow preventer?

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8 Comments

Mike

10/19/2023 08:09:23 am

I wouldn't say "equal" so much as "acceptable in lieu of". The check valve and drop loop minimizes but doesn't eliminate the possibility of dilution. NFPA doesn't mandate which arrangement you must pick. You really are weighing the cost to replace the premixed AF solution if it becomes too dilute vs the cost of an RPZ, expansion tank and forward flow testing the RPZ in the future. Premix AF is rather expensive, but so are RPZs and forward flow tests etc.

Dan Wilder

10/19/2023 08:28:22 am

No, a check valve does not perform the same as a backflow assembly. Even two check valves in line with each other do not perform the same.

The reason for a drilled hole in the clapper of a check valve is to allow thermal expansion of the anti-freeze back into the wet system, that is typically larger and can handle the pressure increase (essentially a very large expansion tank). Without that hole, a listed expansion tank or a pressure relief valve is required to handle that same thermal expansion.

8.6.3.1 would be for a connection to a wet system that "should" already have a pressure relief valve or at least a system that can handle the expansion. The 5' minimum drop is to prevent dilution of the nonfreezing solution as it interfaces with the wet system.

8.6.3.3 shows the backflow (or RPZ) with the expansion tank with no check valve (regardless of wet pipe supply) as there would be no loss of solution for thermal expansion/contraction thus no dilution.

8.6.3.4 shows the backflow without the expansion tank but with a pressure relief valve located above the incoming supply to allow pressure relief (loss of liquid) but would generally lose unmixed or lesser mixed solution due to the slower nature of pressure increase & drop (refill). You can also see that illustrated with the Water ->|<- Nonfreezing Solution delineation at the "A" valve.

SCHULMAN

10/19/2023 09:36:20 am

Dan's answer .... No, not the same.
Drilled holes in clappers went out of style many moons ago.

Anthony

10/19/2023 10:32:30 am

No. The purpose of a backflow device (BFD) is to prevent cross contamination with the water supply and check valves, even in series, does not do that. PRV's would work best of you are concerned about expansion issues but keep in mind a RPZ is still required for any hazardous system, not just foam or antifreeze.

Glenn Berger

10/19/2023 12:38:52 pm

A check valve is not a substitute for an approved backflow preventor.

RYAN HINSON

10/19/2023 01:04:18 pm

The location for the BFP required by your AHJ is indeed referencing the lead-in to your building and not at your antifreeze extension location. A backflow is already going to be required upstream of any non-potable system connection to a potable water supply per the applicable plumbing code for the jurisdiction (See IPC 2012 Section 608.16.4)...including any water-based sprinkler system.

Since you have antifreeze downstream of this connection, an RPZ would be required at the potable water interface upstream of any wet-pipe system per IPC Section 608.16.4.1. NFPA 13 requires 'listed' expansion chambers if the option consisting of "a backflow preventer with control valves" is provided per NFPA 13 Section 8.6.3.3 and Figure 8.6.3.3.

Perhaps it's an oversight, but I see nothing in NFPA 13 requiring a 'listed' BFP for separation between an auxiliary antifreeze system and a wet-pipe sprinkler system (as indicated in NFPA 13 (2022) Section 8.6.3.1.

As such, I want to agree with you that a check valve alone should be sufficient for the intent of this section...as currently written, however, Figure 8.6.3.4 includes mention of BOTH a 'check valve' AND a 'backflow preventer with control valves' where sprinklers are above valve A.

As indicated above, NFPA 13 does not require a listed backflow preventer at this location. One must go to NFPA 24 (2022) Section 5.4.2 to get the definition of a listed backflow prevention device. It says, "Where a backflow prevention device is installed to guard against possible cross-contamination of the public water system, it shall be listed for fire protection service."

Section 5.4.2.1 goes on to say, "Where a check valve or alarm check valve is permitted by the AHJ in lieu of a backflow preventer, it shall be listed for fire protection service."

Neither of these sections apply to the location your query is about IMO. Due to the fact that the BFP itself is optional under certain conditions per NFPA 13, this location is not required to meet the stipulations of plumbing code...since again, this is already handled upstream of the non-potable system piping.

Jesse

10/20/2023 08:21:22 am

No, not really. These aren't the same device

Mark

5/2/2024 10:12:41 pm

If you have an RP at the Anti-Freeze loop, are you required to have one at your riser as well? Or can you be ok with having a DC at the riser??

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A Check Valve Equivalent to BFP for Antifreeze?

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