I am taking on water from a recent high water table. This home has been dry for 12 years. All drains flow away from house. We had 5 inches of water, now a week later its 1-1.5" per day. I can pump it down, but it returns. Can I pump it down, then put a sump pump in or will the high water table create a bigger mess for me?

If my sump pump has an outlet pipe sizing of 1.5" what are the draw backs from using existing 1" pipe? Should I just run all new 1.5" to match the pump? Running up 10 feet, and 50 feet of horizontal then out to an existing 4" PVC to street.

If I understand you correctly, the water is already getting into the house. I doubt that making a hole in the floor for a sump will make it worse unless there is a lot of hydrostatic pressure under the floor.

As to the outlet piping for a sump pump, bigger is better. The smaller the pipe, the greater resistance to water flow and the less your pump will move for a given energy input and time. If at all possible get the output pipe at least as big as the pump outlet. A bit bigger, as in 2 inch, for the 50 ft run would not hurt.

I agree with EPM, a sump pump would help but without a curtain, perimeter tiles at the foundation, it will not be a great fix. If you have a basement with no sump and no tile the correct fix is to jack hammer a trench at the perimeter of the floor, install tile sloped to sump and then a pump. Sump Pit Installation - Don't Let it Get You Down in the Dumps

You should always match the pipe size with size of the pump outlet. Do not reduce. If you are getting lots of water, get 2" pump with 2" discharge pipe...