Pressure Gauge Req'd on Both Sides of Backflow?

1/3/2024

Would you require a pressure gauge on the bottom side of the backflow device?

NFPA 13 says pressure gauges shall be installed above and below each “alarm” check valve or “system riser” check valve where such devices are present.

Is the backflow preventer considered an alarm check or riser check valve?

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11 Comments

Pete H

1/3/2024 07:25:24 am

I could be entirely wrong, so take with a grain of salt:

From NFPA 13 (2016)

7.1.1.2 Pressure gauges shall be installed above and below each alarm check valve or system riser check valve where such devices are present.

8.16.1.1.2.5 A listed backflow prevention assembly shall be permitted to be considered a control valve, provided both control valves are listed for fire protection system use and an additional control valve not required.

8.16.1.1.3.2 A listed backflow prevention devices shall be considered a check valve, and an additional check valve shall not be required.

--

Since the device of the alarm check valve or system riser check valve is not technically present as much as they have a listed backflow device serving their purpose, 7.1.1.2 may not apply.

But I could also see the argument that since the backflow device is considered a check valve, and pressure gauges should be considered required, but I ultimately see that being up to AHJ interpretation of the code. I can read it either way.

Dan Wilder

1/3/2024 07:44:05 am

All references are to NFPA 13 - 2019

Yes, by using the available ports on the assembly. Test cock #2 & #3 provide the outlet locations needed to comply (on each side of the backflow clappers) and is downstream of the butterfly valve for access/maintenance. No different than an alarm check.

Worst case, use the #1 position for a gauge but no reason to add another outlet for a gauge on the supply side. Any service at this location requires building service shutdown of the incoming underground line.

The reason for that location (the pressure gauges) is to indicate an issue with the check valve (clappers of the backflow in this case) so no code/standard driven requirement for additional. It is nice to see if the UG supply is pressurized, but easily checked via cracking the control valve open a little. The control valve (butterfly/OS&Y) already has an indicating means for identifying an open/partial open/closed, closed valve condition.

As to what a backflow is defined as, firstly - the gauge requirement is for a "System Riser" which is defined below. Notice that there is no requirement for a check/backflow valve:

3.3.215 System Riser.
The aboveground horizontal or vertical pipe between the water supply and the mains (cross or feed) that contains a control valve (either directly or within its supply pipe), a pressure gauge, a drain, and a waterflow alarm device.

8.1.1.1 says only 1 gauge is required
8.1.1.2 says 2 gauges are required when an alarm check or system riser check valve is installed

Backflows aren't really discussed as a system riser until:
3.3.46* Control Valve. - A valve controlling flow to water-based fire protection systems and devices.
16.9.3 Control Valves
16.9.3.3.5
A listed backflow prevention assembly shall be permitted to be considered a control valve, provided both control valves are listed for fire protection system use and an additional control valve shall not be required.

Phew....getting all the definitions out of the way early this week!

Anthony

1/3/2024 07:51:37 am

A backflow preventer is definitely not considered an alarm check as it has no flow switch, alarm bell etc. I think the point of the code is to make sure the contractor actually installs the gauges in the ports provided by the alarm/riser check. I can see those getting skipped. I can see why it would be useful to have a gauge on the upstream side of the backflow preventer, but I would not require it as a specifying engineer.

Alex

1/3/2024 08:54:06 am

I do not believe a gauge is required. If there is an issue with the DCVA, it will be noticed during your forward flow test. Curious what others have to say.

sean

1/3/2024 09:03:47 am

The backflow device is not regulated by NFPA 13. If you see backflow protection is dictated by the local plumbing code. Your local plumbing code will dictate where gauges are required. If you use the International Plumbing Code 608.17.4.1 says you need a RP , RPZ, or RPDA device as a fire department connection is a second non-potable source.

Per SECTION 312 TESTS AND INSPECTIONS it appears you need to have the connection to support a gauge but may not required to keep it installed. Either way this plumbing device and shall be regulated by the local plumbing code.

Jack G

1/3/2024 10:04:57 am

To cover your bases( as AHJ ) may require, I ve been ordering the bfp with ports on each side of supply side gr valve. No difference in price, or replace the supply side with one that has the ports, or an os&y with ports. Easy gauge ports.

Casey Milhorn

1/3/2024 11:01:57 am

Lots of great comments. Some different viewpoints I hadn't considered.

I would be concerned #1 of modifying a listed assembly by adding a gauge to it in a permanent way. #2 if added below the backflow, you can get into some contamination concerns with how it's added. Black steel spool piece and mech tee? Galv pipe? The gauge assembly going to be okay with the water dept. before the backflow?

I don't see a need for a permanent gauge here. Backflows are tested annually, and even more often in some areas.

Glenn Berger

1/3/2024 07:15:18 pm

I do require pressure gauges on both sides of backflow preventors.

Having them allows the determination of actual pressure drop across the BFP when preforming the forward flow testing.

A BFP is not an alarm check valve or a riser check valve.

Dave

1/4/2024 11:22:53 am

Glenn, our specs require them too (yet it is never followed), but I was drawing a blank where it originated from.

Glenn Berger

1/4/2024 02:19:34 pm

Dave,

I have no qualms about issuing non-compliance reports when doing field reviews. Most of my clients like when I can quote paragraph numbers when the requirements of a contract are not followed.

Dwight Havens

1/6/2024 08:37:23 am

Another benefit to having a gauge on the supply side of the backflow prevention assembly (BFPA) is that it assures the ability to watch the supply side water pressure during main drain tests. I've seen a lot of confusion on which pressures to observe and record for this purpose, with many tests performed without ever relieving the pressure on the system side of the BFPA, especially on large systems. These results are then worthless in determining any change in the status of of the water supply.

Pressure Gauge Req'd on Both Sides of Backflow?

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