If it is comming out by the front rocker, there is a good chance that it is the drain tube for the Sunroof. My 5 series has the same but I believe that it is on the passenger side. Next time you wash the car, move it to a dry area and see if you see water coming from that area.

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2012 X5 50i ZAP(2VA, 336, 465), ZTP, ZPP, ZPS(6VC), ZCW, ZRC, 322, 4UB, 4NC, 610
2011 ///M3 Silverstone II
2011 X5 50i(lemon)
-- SOLD --
08 550 Msport
07 X5 4.8I sport
04 545i sport
02 4.4i sport
01 540I M/sport
00 SL500
97 SL500