Manifolds that are too small ultimately will limit the department’s ability to flow higher volumes of water. Manifolds that are too large don’t accurately measure lower water flows, resulting in poor-quality finished foam. Dual plumbing of some discharges may allow a department to change the manifold size to best meet its needs. Departments need to work with the apparatus manufacturer to determine what will best meet their needs.

Similar to foam manifolds, each size of foam pump has its positives and negatives. Foam pump capabilities should be matched to the department’s needs. A department should ask:

1] What flow range can the foam pump meet? In CAF applications, concentrates typically range from 0.3% to 0.5% for wet foam and 0.7% to 1% for a drier foam. These percentages equate to relatively low flows of foam concentrate in a Class A application. Departments that require a Class A and Class B system will need to determine what the flow requirements are for each application. The injection rates for Class A and B are significantly different, and a foam pump that meets all your Class A requirements may not come close to meeting your class B needs.

Departments that don’t wish to have both dedicated Class A and Class B foam systems on their apparatus but still want the additional capabilities may consider an auxiliary foam pickup. Typically this is accomplished by adding a standard Class A/B selector valve assembly with the Class B side plumbed to a simple overboard pickup. This system allows the department the option to use Class B foam from pails through the plumbed foam system. Other benefits include the ability to try different types or brands of foam concentrates without needing to dump or flush the foam tank. However, some foam pumps have difficulty drawing foam concentrate from a pail as they typically operate from a flooded state with the foam coming from a foam tank located above the foam pump.

2] Does the foam pump start at a high flow and then reduce its injection rate to meet the desired flow rates? Some foam pumps will start their injection cycles at a high flow and then slowly reduce the inject rate to meet the selected flow. This initial high flow of foam concentrate may result in the increased use of foam concentrates.

3] Does the foam pump have an optional auto-on feature? Some foam pump manufacturers are providing a feature that automatically powers the unit up into its inject mode. In this mode, as soon as the pump operator flows water the foam pump begins injecting concentrate. This is one fewer operational step for the operator, but it could lead to unwanted use of foam concentrate.

4] Does the foam pump adjust for differences in foam concentrates and water? Some systems work volumetrically and inject concentrate in proportion. Other systems use conductivity to maintain the correct proportion. These systems compensate for variations in concentrate and water quality.