Gitzo tripods are favorites among professional photographers and for good reason. They are light, durable, and among the most stable tripods available. However they are far from perfect. The most common complaint is that the leg locks are slow and cumbersome to use. There's not much you can do about that though. The "slow" rotating collar leg locks are part of what makes them so stable and durable.
Another complaint with many models, such as my Gitzo 1228, is that the sections don't drop free and spring back and forth when you are extending/collapsing them . This is because the legs are almost airtight, and so when you pull the sections out, the partial vacuum pulls them back in, and vice versa. The only openings for air to pass through are around the collars which poses another problem. The gaps are big enough that they allow water to get in, but positioned where the water can not easily get out. Therefore, if you are wading in the water with your tripod, water will make its way through the collars and into the legs. It gets trapped in there and will slosh around until you disassemble a section to let it drain.
I'm not sure why Gitzo didn't just design the upper leg castings to have holes for air and water to pass through. If they thought it would reduce debris inside the legs, the existing design just makes thing worst by forcing debris through the wear surfaces of the collar, and trapping it in there. Well... always looking for an excuse to mod something, I thought I would break out the power drill and fix this problem.
First thing to figure out is where to drill. For my Gitzo 1228, I decided on the beveled face on the inside of the upper leg casting. The reasoning behind this was I wanted the hole to face inwards to minimize dust and debris getting in. I also wanted it in a spot that would not weaken the casting, hit the carbon fiber legs where it might propagate a crack, or interfere with the angle lock. Additionally I wanted the hole at the very end of the leg so that it would be easier to purge trapped water. Drilling down the bevel at ~ 30 degrees, the hole actually enters the inside of the casting through the top. Perfect for what I wanted.
You will want to completely disassemble the legs before drilling. It's fairly straightforward, simply remove the bolts, notice the 2 opposing bolts that hold the leg in place need to be torqued at the same time though. Make note of which side the washers face and do one leg at a time so you don't mix up the parts. It probably doesn't matter but if you have an old tripod, these wear surfaces have been broken-in against each other and so you don't want to mix things up. Remove all leg sections so that you don't get magnesium shavings in the legs and on the collars when you drill.
Make sure you hold your drill at an angle close to what you see here. If it's too perpendicular, you'll end up drilling into the hole on top of the casting for the bolt. I used a 3/32" drill bit. It isn't so big that it will weaken the casting or let a lot of debris in, but it's big enough to let a sufficient amount of air in and out and equalize the pressure in the leg.
After you are finished drilling, make sure you clean off all the shavings, especially on the inside of the leg. I just used a paper towel pushed in and out by a thin rod. Bolt it all back together and now you got a Gitzo tripod that is easier to extend and collapse. If you get water trapped inside the legs, now you can just turn it upside down and pump it out by collapsing the leg. Now if only I could figure out a way to make them less expensive.