Water pressure when changing pipe diameter
First, check on what @ThreePhaseEel said then, as a &quot;rule of thumb&quot;, a 2&quot; pipe can carry the flow of 4- 1&quot; pipes, so the 1&quot; pipe will only carry 1/4 of water of the 2&quot; supply pipe. Under a no flow condition the pressure will remain relatively the same but there will be reduced maximum flow and reduced pressure when a large flow is utilized.