Heat or moisture infiltration can cause icing in various areas of a walk-in. This could be caused by gaps in panels, door alignment, propping/holding doors open, or inefficient refrigeration equipment.

Temperature spikes can happen but should stay in a food safety zone. Your refrigeration equipment may need to be serviced or replaced.

Doors can go out of adjustment over time. Heavy usage, propping doors open with heavy objects, unlevel flooring or even the door sweep or gaskets could be damaged, causing the door to not close properly. A door hinge or door closer adjustment can easily correct this issue.

Yes and no. If your refrigeration system is a remote system, it will need to have a drain. The evaporators inside go through multiple defrost times per day/night which melt off any excess ice or frost, turning it to water. If it does not leave the evaporator pan, it could spill out onto the floor causing a slip hazard or worse, cause your evaporator to freeze over and stop cooling properly.

If the refrigeration system is self-contained, there are models of self-contained refrigeration systems that do not require a drain, but use internal moisture dissipation to remove the waste water.

Other options are available if your location does not have access to a floor drain, mop sink or any other drainage access.