Dealing with rope twists mid-pitch
We've all been there: the evil Rope Twist Gremlin decides that they’re gonna mess with you today, and your second arrives at the anchor with a rope in a mess of pigtails next to their tie in point.
Who knows how the twisties got there? It's your job to get ‘em out!
Once you start getting rope twists, you don’t want to continue with them. It can cause all manner of problems, ranging from problematic belaying, to a rope-snagging snarl at the anchor when you (try to) pull your rappel rope. (I've had some bad experiences with both of these issues!)
On a multi pitch route, solving this will probably mean that the second needs to completely untie from their end of the rope. Yes, this is little nerve-racking when you’re way off the deck!
There are a couple of ways to handle this.
If you have a tether, you can clip in direct to the anchor, untie from the rope, work the twists out, and then tie in again. Ideally, have your partner check every step of this operation.
If you don't have a tether, you can try a technique called the backside clove hitch. The photo above shows it pretty clearly. On the backside of the leader’s clove hitch tied to the anchor, the leader can tie a second knot. The second clips to this knot with a locking carabiner on to their belay loop. Now, the second can untie their retraced figure eight, remove the rope twists, and then tie in again. Have your partner check your knot after you tie in.
Here's a nice video from IFMGA certified guide Karsten Delap that shows the technique. The “removing rope twist” section starts about 4:05.