Abstract: Discharge ports of liquid floor finish applicators are known to clog if proper steps are not taken immediately after use. Complicating this clogging problem are the facts that floor finishes are formulated to dry quickly when exposed to air and applicator cleaning creates waste and takes considerable time and effort. Accordingly, applicant's invention addresses the problem of clogging by using a liquid reservoir to enclose the applicator's discharge port thus preventing it from clogging when not in use. To illustrate applicant's invention, a backpack floor finish applicator system dispenses liquid floor finish through a hose and a pump that forces the finish through a nozzle onto the floor. The invention uses a non-contact switch that activates a light which alerts the operator when the nozzle is exposed to air which will cause clogging thereby reminding the operator to position the nozzle within the liquid reservoir when not in use.