This is a normal amount of water left in the sump of a washing machine. If the machine is not used for a day or two then the water will go stagnent and start to smell, especially if it's a warm day. Low temp washes encourage this as bacteria can survive in washes that do not exceed 60 c. A rinse would be better than emptying filter too often as the seals will wear and will leak from filter.
paul
June 2010