A Foam tank is a very desirable add on for any engine incorporating a foam concentrate proportioning system. A properly designed, built, and maintained foam concentrate storage tank has several components as required by NFPA: 1) a
lockdown, sealable lid with a vent valve; 2) an electronic floating trip switch to signal a concentrate proportioning system that concentrate is low; 3) a discharge line shut off valve (for maintenance and line breaks). The discharge line must be at the low end of the tank and can also act as a drain line. And 4) A clean-out trap (wye) to catch any debris that might enter the foam
concentrate tank (you would be surprised).
Even depending on the concentrate systems capability to pull a draft, the foam tank should be mounted higher than the concentrate pump. Concentrate tanks can be any size based on the fire department’s needs.
If a truck has a broken or no foam concentrate tank, a siphon or pick up tube can be used along with a 5 gallon concentrate bucket. However, items 1-4 above would not be available if needed. And, if the apparatus has pump and roll capabilities, the bucket will have to be secured. The foam level in the bucket would have to be constantly monitored as the bucket has no way to signal low concentrate leaving the system to continue running without concentrate (Not a good thing!!).