Monday, May 9, 2016

Vane Type Water Flow Switches

Vane Type Water Flow Switches are used to generate a fire alarm signal based on a water flow discharge event from a wet pipe fire sprinkler system.  These devices are tested at least annually, sometimes quarterly.  These devices sometimes fail, and often they are incorrectly installed, maintained or tampered with. 

Pictured below is a small pipe vane type water flow switch (hereinafter flow switch).  This one has been removed from service. The arrow is pointing to the flexible plastic vane [which fits in the pipe].

Next, a wet riser is shown with two flow switches, only one is needed.  The top switch likely failed, wiring was disconnected and moved to the new [presumably] working switch. 

A close up of the above install below.  The top switch should be removed, the hole plugged (which won't be easy):

Below, an installed flow switch with a missing cover:

Below we have an in situ photo of an improper field modified flow switch.  The purpose of the modification is o defeat the switch, stop the vane from signaling.

Below is another switch with the same improper field modification.  This time it is a "black tywrap", making detection even more difficult:

For clarification, the photo below shows the same switch with the improper defeat device ("black tywrap") removed.  This is how the switch gear is suppose to look:

Below, a switch has "signage" attached, to aid inspectors in locating the gear from below (from floor level).  You will almost never see this on field installations:

Here is an in situ flow switch install, it is mounted on the side of the pipe.  It is recommended to mount this on the top of the pipe.

Another install below, the switch cover is incorrectly mounted.  There appears to be no wiring to/from this switch.  The switch would like not report water flow to the fire alarm system.  The vane may or may not move unrestricted with the cover in  this position.

Below, two water flow switches are shown.  Both appear not to be installed in accordance with manufacturer's instructions (installed at least 24" away from a valve or drain).  This is a possible design/install error.

For reference for the above installation see:

For another view of the same riser:

And another 2 sites, another 2  more examples:

Below a new system installation, arrow points to water flow switch:

A close up of the switch installation above shows evidence that the technician left the tamper screw removal tool behind:

The next series of photos show, as found on arrival, a disconnected flow switch [hanging in mid-air] and a flow switch on another riser with a missing cover:

Close ups follow:

Following switch may not be installed in accordance with manufacturer's instructions:

Switch below is mounted close to bottom of pipe, this is not recommended.

Switch photographed below is not wired, may not transmit signal to fire alarm control panel.  Control valve tamper may not be wired either.

Another site with the tamper screw removal tool left in the switch cover:

The following series of photos show a flow switch removed from service, electrical contacts failed, likely due to corrosion.  Corrosion may have resulted from a leak between water filled pipe and switch internal mechanism:

The same switch as above, except with vane/paddle attached:

The following two (2) photos show the above switch in situ, the wires were found cut, the FACP was found "green".  A technician had 'resistored" out the switch.  This was likely due to faults (trouble conditions) that the technician was unable to solve or repair.

Flow switches should not be painted:

And another one:


  1. Nice post. I was checking constantly this blog and I am impressed! Extremely helpful information specially the last part I care for such info a lot. I was seeking this particular information for a very long time. Thank you and good luck.
    Liquid Level Sensor

  2. Your welcome. I haven't updated the site in a few months due to travel and work, currently in Czech Republic, will be returning to Africa for work soon. Hope to update the site then. BB