The new Greenstar System mini filter is a fantastic addition to the much sought after Worcester product range. The filter has been designed to be easier than ever to install and service with performance being improved and coming in a compact size.. The filter captures contaminants before they reach the boiler contributing to a longer-lasting, healthier system, central heating system water accumulates harmful dirt and debris, such as rust and solder fragments shed by radiators and boilers, all of which can cause considerable problems. The Worcester Greenstar System Mini Filter has been specifically designed to combat the damaging effects of system debris and pollutants by capturing contaminants before they reach your boiler. The new Greenstar System Filter has been designed to combat.