Dow Filmtec LP-4040 Low Pressure Membrane None Imported Features the industry's thickest feed spacer (34 mil), which lessens the impact of fouling Dow Filmtec membranes are available in a variety of sizes to meet a range of space requirements May be cleaned over a wide range of pH levels (pH 1-13) for maximum cleaning effectiveness Maximum Pressure Drop: 13 psig Free Chlorine Tolerance: &lt;0.1 ppm