RO Output Restriction?

I have a Deer Run 250 that has 1/2" I.D. flexible lines for the permeate and concentrate outputs. I need to extend my permeate line so that I can reach some extra storage tanks. I'm using a 1/2" insert fitting to add the extra line. The insert fitting reduces the I.D. of the line a bit. I didn't measure it, but I can see the ID of the barbed end is a bit smaller than the NPT side.

Will the smaller ID on the permeate create a restriction that would have any kind of effect on the flow rates of the RO itself?

You will be fine, if using the same ID tubing that is comming off the RO.
1 or 2 fittings in a line would not create enough restriction to effect anything.

Bricklayer is right, but if you use a SS insert coupler the restriction will be far less, beside it will last forever, the plastic ones fail after a few years and could fail and pump a lot of permeate on the ground, as well as if the outlet end of the line is in the permeate it could siphon that tank empty.

You could use an external compression coupler that would not restrict flow. The other option would be if you are adding a lot of distance, would be to change the hose at the RO to 5/8 or 3/4 in however long you need for less restriction over the distance.

All good info. Thanks for the input.