Yes, WaStop causes the lowest pressure loss of all the available non-return valves on the market. A pipe system works using pressure differences. When the upstream pressure is higher than the downstream pressure, this allows flow in the correct direction. Anything added to a system subsequent to the original installation/design will change the resistance in the pipes. Use of the WaStop non-return valve will slightly limit the system, but the pressure loss will be less than with any of the other non-return valves available.