Another area departments need to be concerned with is discharge plumbing, especially in the cases where departments specify a CAF-capable deck gun or large-diameter hose discharge. In the majority of foam systems today, the water flow being supplied to all foam-capable discharges is measured at a single point in the plumbing. This usually is the smallest point in the foam manifold. There are several ways apparatus manufacturers can provide these additional capabilities with fewer problems.

The first option is to have all foam-capable discharges, including deck gun and ldh, plumbed only off the foam manifold. This option presents the simplest and cheapest method of providing foam to the desired discharges; however, it also provides the greatest limitations to the department. With this method, all discharges plumbed to the foam manifold will be able to flow only foam. This design would prevent a department from running clear water from the deck gun while foam was being used.

Departments requesting a CAF-capable deck gun should strongly consider adding a static mixing device to properly agitate the caf solution. These devices work well while flowing compressed-air foam, but create a significant pressure drop when trying to flow water only. A single point of plumbing will require higher master pump discharge pressures when flowing high volumes to overcome either the restriction of the narrowing of the foam manifold or the static mixing devices.

Another option is to have all foam-capable discharges plumbed off the foam manifold with the deck gun or ldh discharge being dual-plumbed off both the foam manifold and the clear water manifold. This option provides the department with the ability to flow foam or clear water out of their high-flow discharges. Each discharge is provided with two sets of valves and pressure gauges, one set plumbed from the foam manifold and the second set from the clear-water manifold. These increased operation abilities are achieved at a higher cost due to additional plumbing, valves and gauges, as well as additional pump operator space.

Foam finish

Another area that departments must consider when speccing CAFS is the foam system itself. This typicality consists of two main components: the foam manifold where the water flow is measured, the foam is injected and the foam solution is delivered to specified discharges; and the foam pump, which delivers the proper amount of foam concentrate from the foam tank to the foam manifold.

Most manufacturers use a foam manifold with a single measuring point and foam concentrate injection point. These manifolds are premanufactured in several sizes or may be custom-built to meet specific requirements. Departments should be aware of the size of the manifold and of the possible restriction or limitation the manifold may place on the performance of the apparatus.