Nappies are heavily soiled laundry, warm or hot water is the most effective way to remove soiling. All laundry detergents can be used in cold, warm or hot water, however, the effectiveness of laundry detergents is reduced as water temperature decreases. A hot wash will outperform a cold wash.
Higher water temperatures allow fibres to relax, allowing surfactants and enzymes to penetrate better.
The elevated temperature supports the reaction process of the detergent and many components in the detergents (e.g. sodium percarbonate and enzymes) either do not activate, or only partly activate in cold water.
Heat weakens the binding forces of the soiling to the fabric, therefore soiling will dissolve more readily the higher the temperature, textiles are going to be cleaned better with increasing temperature.
Through significant Facebook member feedback, and extensive Admin testing, it has been concluded that using only cold water does not work in the long term, in regards to ensuring that nappies are completely clean and smell free out of the wash.
While cold washing saves money on energy costs, the down side is eventually smells will occur. Higher washing temperatures result in higher microbial reduction levels, compared to cold water wash.
Modern front loader machines heat their own water. Top loaders require a hot water tap connection. If a hot water source is not available, or limited, an option is doing a cold pre wash cycle, then (carefully) bucketing in warm/hot water into the machine for the main wash.
 Textile Quality Depletion due to Household Machine Wash – Ways to Measure and Impacts of Wash Duration and Temperature on Textiles
 Antimicrobial Efficacy of Laundry Detergents with Regard to Time and Temperature in Domestic Washing Machines: Marlitt Honisch , Britta Brands , Mirko Weide , Horst-Dieter Speckmann , Rainer Stamminger and Dirk P. Bockmühl