How would this hold up to heat tape on water lines ?

This product can be used on water pipes.

Hello: Reflectix is basically shiny bubble wrap made from plastic, with a maximum service temperature of 180 degrees F. In addition, it will not be effective on pipes because you must create a sealed air gap when you install it; this air gap provides almost all of the claimed R-value. Lowes sells standard foam and fiberglass pipe insulation that is much more effective. For example: Frost King, Lowes Item # 24434 Model # P12XB/6. Even though these foam sleeves are self adhesive, be sure to seal the slit on the side with foil HVAC tape. See: 3M, Lowes Item # 350444 Model # 3340. If you live in an area with very cold winters, you can add another layer with fiberglass insulation sleeves that will fit around the foam. See: Frost King, Lowes Item # 145686 Model # F14X. Seal the slit on these sleeves with the same foil HVAC tape. I hope this is helpful.

Reflectix can withstand temperatures up to 180 degrees F. If the heat tape is under that temperature it should work fine. You would need to check with the heat tape manufacturer because some do not recommend using reflective products with their product.