Our house is a 3.5 bath with a sink and dishwasher in the kitchen as well as cloths washer in the laundry. The house is a 2 story older farm type house. The main coming into the meter is 2 inch. What happens after that is it turns to a 3/4 for about ten feet then everything branches of that to 1/2.

One bath room is on the second floor the kitchen, laundry room, a full bath and a half bath are on the main floor and a full bath is in the basement. Would it help to replace the existing 3/4 with and 1 inch and the 1/2 with 3/4 as far as I can without opening walls.

Also I am thinking about using PEX Vs copper but I am not sure about it. Is it really safe or am I just being paranoid?

Since you've failed to give me the material the pipes are made and their age I can't make much of a comment except to say that a 3/4" main is normal. As for the 1/2" branches, if there are no more then 3 fixtures using a 1/2" branch that too falls within code.
"Would it help to replace the existing 3/4 with and 1 inch and the 1/2 with 3/4 as far as I can without opening walls."
Not if you leave pipes that are choked with rust or mineral build up in the system.
"Also I am thinking about using PEX Vs copper but I am not sure about it. Is it really safe or am I just being paranoid"
While Pex had its problems at first they have been corrected. Pex is more "user friendly" the copper to install and it's a proven fact that plastic will outlast copper. Good luck Tom

Its copper it doesn't look that old nothing has turned green or anything. If the pipes are all choked that run into the wall what's the easiest way to replace these without opening up the wall?

Its copper it doesnt look that old nothing has turned green or anything. If the pipes are all choked that run into the wall whats the easiest way to replace these without opening up the wall?

Before I started replacing pipes I would begain to check the faucets for mineral build up that may be blocking the flow. Let me know what you find.
Regards, Tom

The bath room sink in the upstairs was pretty bad but the rest seem fine. We notice the problem mostly in the upstairs bath room would it help if we ran 3/4 copper all the way up there instead of the 1/2? Believe it or not I can actually get at those pipes pretty easily.

Thanks again Tom you are a ton of help.

The bath room sink in the upstairs was pretty bad but the rest seem fine. We notice the problem mostly in the upstairs bath room would it help if we ran 3/4 copper all the way up there instead of the 1/2? believe it or not I can actually get at those pipes pretty easily.

Thanks again Tom you are a ton of help.

Increasing the volume by going to 3/4" isn't going to help if the you have a blockage in the supplies or faucet. I think you're starting at the wrong end. Start where there pressure's the weakest and work back until you run into good pressure. Then start replacing from there. Good luck. Tom