Moisture accumulation is normal. This results from condensation of the pressurized steam vapor as it cools upon contact with the surface. The longer you clean in one area and the higher the steam setting you use, the more moisture will build up. Wipe away this excess water with a towel or cloth periodically as you go & switch out saturated mop cloths as needed.
Models: STEVA+ STP010 / STEAM+ SMP010 / STEAMPAC+ SMP110 / STEAM FLR SMP002