There are two part chemical tanks in various sizes to "spray" foam chemical in that expands and grows. We will also "back fill" with dry foam chuncks that had been extracted as filler. We continue to spray foam in until the spa is again well insulated.
The size of the job, determines the appropriate size of the tanks. Spot repairs are done with 1 to 22 "board" feet and get progressively larger. We use tanks of 180 board feet so we are prepared for any job.