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 There is no point introducing pvc into the supply line.
 I would:
 Tee off from your main line with PEX crimp fittings
 Run a branch over to the RO unit.
 Add a ball valve where convenient to operate.
 Then step it down to a 1/4" quick connect to go to the RO unit.
 
 This ensures that the main lines in the house are using pex crimp rings.  The quick connect is after a valve so that if any issues arise you can ensure that its off.
 
 Personally I don't trust the shark-bit fittings or any other quick connects.
 The slightest damage to the exterior of the pipe before installation or the o-rings during and you have potential for failure.
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