Ratio-Flow Controllers

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The Chemguard ratio flow controller is a device designed to meter the correct amount of Chemguard foam concentrate into the water stream over a wide range of flows and pressures with minimal pressure loss.  These devices are used in conjunction with either a bladder tank or a foam pump proportioning system.  Chemguard ratio flow controllers are UL Listed and FM Approved with certain Chemguard foam concentrates.  Typical applications include flammable liquid storage tanks, loading racks, aircraft hangars, and heliports or anywhere flammable liquids are used, stored, processed or transported.

The operating principle of the controller is based upon the use of a modified venturi.  As water passes through the inlet nozzle, pressure is reduced in the annular area of the nozzle.  This reduction allows the metering of foam concentrate into the water stream through a foam concentrate-metering orifice.


Chemguard offers the ratio flow controller body in five models.  The 2-1/2” ratio flow controller is a threaded controller designed with a 2-1/2” female NPT threaded inlet and 2-1/2” male NPT threaded outlet.  The 3”, 4”, 6” and 8” ratio flow controllers are “between the flanges” units designed to fit between two ANSI 150 lb. pipe flanges. Only the recovery section protrudes into the system water piping.  To ensure a complete gasket seal when installing between flanges, each face of the controller is machined with 20 grooves per inch.

The ratio flow controller body is cast from ASTM 85-5-5-5 brass.  The inlet nozzle and metering orifice are machined from SAE #72 Brass.  The inlet nozzle set screws and metering orifice retaining ring are of stainless steel.

The inlet nozzle is secured by two stainless steel set screws.  This allows the nozzle to be removed from the controller for cleaning and/or repair.

Metering orifices are sized appropriately for each specified type and percentage foam concentrate.  A stainless steel retaining ring secures the metering orifice in place.

The controller body is clearly marked with a flow direction arrow and label to identify the type of foam concentrate and injection percentage ratio.


The following table lists the nominal flow range for each size ratio controller.  The flow rates may vary when using other foam concentrates.  Please consult the Chemguard Engineering Department for specific applications.

2-1/2” 130-400 (492-1514) 40-400 (151-1514)
3” 245-700 (927-2649) 70-750 (264-2839)
4” 400-1500 (1514-5678) 200-1600 (757-6056)
6” 960-3000 (3633-11356) 300-3400 (1135-12870)
8” 1510-4500 (5715-17034) 500-5500 (1892-20819)


  1. To ensure correct operation of a ratio flow controller when used with a bladder tank, the pressure of the foam concentrate at the controller must be within 2 psi of the incoming water pressure.
  2. To ensure accurate proportioning over the flow range of the controller, minimum water inlet pressure of 30 psi must be available during operation of the system.
  3. Please review the controller dimension table for information on the minimum recommended length of straight pipe required upstream and downstream from the controller.

Technical Drawings


Ratio Flow Controller Size (Model) Dimensions
A B C D ***E F
in. (cm.) in. (cm.) in. (cm.) in. in. (cm.) lb. (kg)
2-1/2” (CPC2.5) 4.3 10.9 2.40 6.10 6.9 17.5 1 NPT 12 31 8 3.6
3” (CPC3.0) 5.3 13.5 2.50 6.35 6.3 16.0 1-1/4 NPT 15 39 12 5.4
4” (CPC4.0) 6.8 17.3 2.75 6.99 8.0 20.3 1-1/2 NPT 20 51 22 10.0
6” (CPC6.0) 8.5 21.6 3.25 8.26 12.4 31.5 2 NPT 30 77 38 17.2
8” (CPC8.0) 10.9 27.7 3.55 9.02 12.4 31.5 2-1/2 NPT 40 102 73 33.1

*** Straight pipe length required upstream and downstream.


A minimum of five (5) pipe diameters should be allowed at the inlet and outlet of the proportioner.


Foam Concentrate Type Ratio Flow Controller Part No.
2-1/2” 3” 4” 6” 8”
1% AFFF   EF10236  *EF10243  *EF10250   EF10257   EF10264
3% AFFF **EF10237 **EF10244 **EF10251 **EF10258 **EF10265
3% AR-AFFF **EF10238 **EF10245 **EF10252 **EF10259 **EF10266
6% AFFF   EF10239   EF10246   EF10253   EF10260   EF10267
3%/6% AR-AFFF @ 3%  *EF10240  *EF10247  *EF10254  *EF10261   EF10268
3%/6% AR-AFFF @ 6%  *EF10241  *EF10248  *EF10255  *EF10262   EF10269
2% High Expansion   EF10242   EF10249   EF10256   EF10263   EF10270
2% C2 (VEEFOAM)  *EF10322  *EF10323  *EF10324  *EF10325   EF10326
3% FP   EF10518   EF10519   EF10520   EF10521   EF10522

* UL Listed
** UL Listed and FM Approved
(Note:  For FM Approved unit, complete approved system purchase required, i.e. ratio flow controller, bladder tank, foam concentrate and discharge device.)