My Holding Tank heater is flappin....

As far as I know, all waste tanks in a typical class C & B+ are completely exposed to the elements. A Super C might be different. Because it is so, many manufactures fully insulate their heated waste tanks.

Since you are down under gluing & taping, why not add a 1/4" thick silver-backed insulation blanket in the process so the heating pad is so much more effective? You can buy such insulation by the roll, cheap at home improvement centers. Between contact cement (or special 2-sided tape) and single-sided EternaBond tape, it won't go anywhere.

Don't forget to insulate the top of the tank as best you can. The better the coverage, the better the heat is retained inside.

I put in my own heating pads and reinforced their adhesive with double stick 3M tape that is recommended for adhering solar panels to the roof. Yes, I cleaned everything well before I taped them on. I also put reflectix over the pads to insulate the heater a bit. My tanks are not enclosed.

I have this same issue on my View. Spray adhesive does not seem like it would be enough.

Charles

Clean it up and clean tank area around the pad

Get a can of spray adhesive.spray light coating on tank and pad
Place pad against tank and hold firmly..........pressing pad flat

Then use EternaBond Tape around the edges making sure pad lays flat/tight against tank and to seal edges so it doesn't come down again