PREVIOUSLY, A 12 "PIPE FOR PROTECTION OF A FUTURE PIPE WAS REQUIRED TO USE A TUNER FOR THE SPECIAL CROSSING, HOWEVER, THANKS TO THE 12" PIPE EXISTING IT COULD AVOID THE WORK TO USE TUNER, NOW IN STOCK WE HAD NO TDW CAPS 12 "x 6" we only had 10 "x 6" caps, so in the diagram you can see that there is a double pipe to protect the 6 "pipe, it should be made clear that the only pipe that has fluid is the pipe. 6 ", the 10" and 12 "pipes only serve as protection, however to avoid corrosion and for possible accumulation of gases is designed venting!