In a single-riser foam system, where is the water source feeding the bladder located relative to the system control valve?

• A. Above the system control valve
• B. Below the system control valve
• C. At the same level as the control valve
• D. Far away from the valve

Answer: (A)

In a single-riser foam system, the bladder must be charged with water so it can push the foam concentrate into the discharge path when the control valve opens. Having the water source feeding the bladder located above the system control valve creates a hydrostatic head that helps water flow into the bladder as soon as flow begins. This gravity-assisted feed ensures the bladder fills quickly, air pockets are minimized, and the system achieves immediate pressure to proportion foam correctly. If the water source were below or at the same level as the valve, there’d be less or no gravitational assist, potentially slower filling and less reliable actuation. A distant source would reduce pressure and slow the response.