Just a post to share a shocker we discovered this week. Had to run a low volume drain line through two walls from an espresso machine to a floor drain. Opted for braided PVC flexible hose so we could navigate the fall line and the bends and turns. After drilling a hole in an old stucco wall (now an interior wall) through the interior drywall, the hose was fished through. On the stucco side, the newbie used fast setting cement to pack the edges of the hole. On the drywall side ... to discourage mice ... newbie used Fire Block foam liberally. Once the connections were made, we tested the drainage and to our surprise, there was a blockage somewhere. (?) After much fussing, I re-opened the stucco wall and checked the inside. The foam engulfed the hose, no mouse bites, ... but ... when I wiggled the hose and bits of FOAM started seeping back toward me in the blocked water! Then water started seeping around the hose. After some tugging, everybody was startled: The Fire Block had dissolved the hose and expanded into the line, blocking the drain! LESSON: Do not apply Fire Block to PVC hoses. SOLUTION: New hose inserted and all penetrations filled with fast-setting cement.