The AF soap not only will keep the lines from freezing. (KR works for me but you need to vary the dilution) But if a customer comes in and the temp has been below freezing fro a while the non AF foam soap may very well freeze as it is applied. Even if you use warm water for the Foam Brush the air injection brings the temp down as does the 50 foot or more run from the equip room to the brush head.How well do the antifreeze soaps work in foam brushes? I weep now, thinking about going to the antifreeze soap. My supplier said the purge system was not worth it. Thanks