I have a drilled well. The expansion tank and pump controls and whole house canister filter are all down in the crawlspace. A space that as I get older, I like to visit less and less. I want to move the whole house filter, the pressure control switch and the pressure gauge up into a room on the first floor. That would place all this maybe 10' downstream of the expansion tank.

The new configuration as I envision it in the crawlspace, would be test valve, check valve, tee to expansion tank (with isolation valve and pressure relief valve.) Up in the house, ball valve, tee to pressure gauge (with isolation valve,) then pressure control switch, then filter.

I've spent hours on the internet looking for a source explaining why the pressure control switch and gauge are placed just before the expansion tank. I can find nothing.

Thanks for reading and I hope you can help with this.

I've spent hours on the internet looking for a source explaining why the pressure control switch and gauge are placed just before the expansion tank. I can find nothing. Here's some typical installations,(see image). Well for one thing the control box's attached to the pump and the gage could just as well install behind the expansion tank but it's handier next to the pump where there's a threaded outlet for it on top of the impeller cage.

The new configuration as I envision it in the crawlspace, would be test valve, check valve, tee to expansion tank (with isolation valve and pressure relief valve.) Up in the house, ball valve, tee to pressure gauge (with isolation valve,) then pressure control switch, then filter.
Test valve, Why would you want to put a test valve on the suction line?

Check valve, tee to expansion tank (with isolation valve and pressure relief valve.) This would put the expansion tank on the suction line. And why all the stuff on the bladder tank. Please explain why a PRV is needed?

Up in the house, ball valve, tee to pressure gauge (with isolation valve,) then pressure control switch, There's enough problems with the small pressure line from the pump to the control box. You would increase the length of the tube by how much?
Bottom line? I think the expense of moving the system up just to make it easier on yourself is a unnecessary expense and besides it wouldn't work the way you've laid it out. Just my opinion. Good luck, nTom

The pressure switch needs to be as near the pressure tank as possible. That's why they put the thread area for gauge and switch on the tank tees, as Tom said. If the pressure switch is to far away, it can cause quick cycling of the pressure switch, in turn burning your pump out prematurely. I don't think I would waste the time and money just to find that it doesn't work quite the way you planned. Sorry. If you really want sfuff out of the crawlspace, find an area where everything can me moved up. This way you won't have to go down there to change anything ever.

I remember a post several months ago from guy who was having problems with his well system. It turned out that, at least according to him, his pressure switch being so far from the tank was the problem. When he moved the switch close to the tank, the problem vanished. So I wouldn't move the switch. The switch shouldn't need maintanence anyway. Should be a "set it and forget it" type of thing.

I would suggest you keep the PRV. It's purpose is to prevent pressure from building to dangerously high levels in case your switch sticks "on" and the pump just keeps running.