Since there is a national law in Japan that requires annual pumping of all onsite systems, our best long term sludge accumulation data comes from Australia where it was determined that average time to reach pumpout depth is every 4 years. (Please refer to page 3 of the Technical Summary). Fuji Clean USA requires that sludge be measured at each 6 month service visit. As directed in the Fuji Clean O&M Manual, system pumpout should occur when sludge levels reach 24” in the sedimentation chamber (first chamber) or 18” in the anaerobic chamber (middle chamber). Based on “normal” full time household water use, we therefore recommend pumpout once every 2 years with higher frequency for higher hydraulic or organic strength flows – particularly if a garbage disposal is being used.