Hello Martin These pressurisers are made to increase the price in lines of driving with minimum precision. you place a pressurizer in a line that requires more price and we do not place it where it is not necessary. (Surely you already know that) Of course, in a 1 1/2 "pipe, the price and the flow are reduced if you place a device that reduces the diameter through which the water passes. However, you are placing a pressurizer that promises you (the manufacturer) to have a flow of 30 LPM, this means: if your pipe goes through a flow less than 30 lpm, with the pressurizer you will get 30 lpm. take into account that in the installation of an apparatus like this, it is recommended that you install it near the place of use (shower, sink, sink, etc.) and not after the water tank, since the price provided by the pressurizer would be distributed in the whole house and you wouldn't see much difference when using all the water intakes. Regards Martin I hope it helps you