Back pressure question

[Muleman]

My well is over 25 years old and plumbed with 1” black poly.  Haven’t used it for years since hooking up to county water.  Bought a CSV125 to hook up so we can use the well to water garden, yard, livestock and small pasture.  Only concern is back pressure and the old black poly.   The well supply line comes into the basement where I will install CSV and then connect to the hydrant line.  Question is if I use 1.25” pvc to connect supply line to csv and 1.25” to connect to hydrant line(about 10’) will the larger pipe change the back pressure?   

[Muleman]

Actually what i bought was PK1A sidekick kit.

[Cary Austin]

The pipe size has nothing to do with back pressure.  The back pressure will be whatever your pump can build.  Back pressure is normally less than 150 PSI unless the pump is way oversized for the water depth.