It's the
length of the output hose that's important, the input hose is irrelevant. That's why SHURflo's so-called
pump silencer kit doesn't live up to it's name - the two hoses are each only 3' long. :R
Prove it to yourself - remove the pump entirely and put it on your workbench, drop a short hose into a container of water, and connect a looped 25' length of potable water hose to the output. Turn the pump on and what will you see? ... the looped output hose where it's connected to the pump will vibrate like crazy but as you look further along the length of the hose you'll notice the vibrations diminish appreciably and at the end of the hose there's little to none. No amount of pump isolation, wrapping hose in foam pipe wrap, adding an accumulator tank, nothing will come close to dampening pump vibration as will an extended length of output hose.
But hey, if you choose to not believe the video proof I provided then go ahead and ignore this solution which absolutely
does solve the problem. :R