Approximate water flow 20-35LPM.10” by 4.5” whole house system was good value, better for family less than 5 members. Approximate water flow 25-40LPM.20” by 4.5” whole house system was highest in value, adequate water flow even for double story house with low water pressure supply. Designed for high flow and numerous consumption user.All the water flow(LPM) marked for reference only, actual flow depend on pressure supplied, size of piping and design of water circuit. Go for larger capacity to avoid insufficient water supply.All inquiry welcomed, please provide accurate information of water source (city, rain, bore), water nature (chlorine, turbidity, bacteria), floor plan (single double story, No. of toilets) and how many people in the house. Kill 99.99% Bacteria his system is designed for both mains and rainwater supply to kill 99.99% of bacteria in untreated water supplies. UV technology has been trusted as a safe, cost-effective way to purify water and eliminate harmful microorganisms. It is a proven endorsed technology that is currently being used by thousands of cities, bottled water manufacturers and homeowners around the world. UV does not change the taste, odor or color of the water. More effective than chlorine: Unlike chlorine, UV systems are effective against both Cryptosporidium and Giardia. UV systems are capable of treating a single faucet or an entire home in a minimal amount of space with the only maintenance being an annual lamp and filter replacements. If you are on tank water this is a perfect cost effective quality combo that will offer complete protection against Bacteria Coli, Giardia and Cryptosporidium.