3.5"
Maximum PSI rating is on the outside rating of the pipe
A PVC pipe 2,640 feet long with an inside diameter of 10 inches has a volume of: 1,440 cubic feet.
A standard water line PVC pipe typically has a width (diameter) of either 1/2 inch, 3/4 inch, 1 inch, or 1.5 inches.
Typical weight and dimensions of PVC and CPVC pipes are indicated in the table below:PVC and CPVC Pipes - Schedule 40Nominal Pipe Size(inches)Outside Diameter(inches)Minimum Wall Thickness(inches)Nominal Inside Diameter(inches)Weight(lb/ft)PVCCPVC1/20.8400.1090.6220.160.173/41.0500.1130.8240.210.2311.3150.1331.0490.320.341 1/41.6600.1401.3800.430.461 1/21.9000.1451.6100.510.5522.3750.1542.0670.680.742 1/22.8750.2032.4691.071.1833.5000.2163.0681.411.5444.5000.2374.0262.012.2055.5630.2585.0472.7366.6250.2806.0653.533.8688.6250.3227.9815.395.811010.7500.36510.0207.558.241212.7500.40611.93810.0110.891414.0000.43813.12411.801616.0000.50015.00015.43PVC and CPVC Pipes - Schedule 80Nominal Pipe Size(inches)Outside Diameter(inches)Minimum Wall Thickness(inches)Nominal Inside Diameter(inches)Weight(lb/ft)PVCCPVC1/20.8400.1470.5460.200.223/41.0500.1540.7420.270.3011.3150.1790.9570.410.441 1/41.6600.1911.2780.520.611 1/21.9000.2001.5000.670.7422.3750.2181.9390.951.022 1/22.8750.2762.3231.451.5633.5000.3002.9001.942.0944.5000.3373.8262.753.0555.5630.3754.8133.8766.6250.4325.7615.425.8288.6250.5007.6258.058.831010.7500.5939.56412.0013.091212.7500.6871137616.5018.01414.0000.75012.50019.301616.0000.84314.31425.441 lb = 0.4536 kg1 ft (foot) = 0.3048 m1 in (inch) = 25.4 mm
3.75
It should, are you sure your pvc pipe is round
What schedule pipe?
Water flow rate half inch PVC pipe 65 psi?
It depends on the pipe schedule and diameter... For example. Schedule 40 1 Inch pipe has a minimum burst pressure pressure rating of 1440PSI and an operational PSI of 270. Google can provide a complete chart. Just search "PVC Pipes - Pressure Ratings"
Probably the wrong size flange. Is the flange a toilet collar? If so the pipe is probably 4 inch.
Not very much, but it will depend on the diameter of the conduit- and you did not tell us how big. It comes it different sizes.