revit二次开发安装部分管道算量

怎么根据管径计算水管工程量
只会计算全部管径加到一起的

 //遍历全部水管


            FilteredElementCollector pipeCollector = new FilteredElementCollector(doc);
            List<Element> pipeList = pipeCollector.OfCategory(BuiltInCategory.OST_PipeCurves).OfClass(typeof(Pipe)).ToList();
            double pipeLength = 0;
            foreach (Element element in pipeCollector)
            {
                Pipe pipe1 = element as Pipe;
                pipeLength += element.LookupParameter("长度").AsDouble() * 0.3048;
            }
            TaskDialog.Show("工程量统计", "水管：" + pipeCollector.Count() + "个\n" + "总长度：" + pipeLength + "mm");