Now the (seatpost and QR) has been practically replaced by an (internally routed riser setpost) tightened with a torque wrench.

I disagree with the accepted answer here - sometimes above 1 liter of water accumulates. And stays there for a month.

But the old advice of "remove the seat, leave bike upside down overnight" is not practical anymore. Now what?

  • Do you have access to a compressor ? A stream of dry compressed air can help, more so if its an old compressor with lubricating oil in the airflow. How does so much water enter your fame ? I'd be looking to block that entrance to reduce the problem, or stop riding in deep water.
    – Criggie
    Mar 9, 2020 at 7:37
  • My bike came with a hole drilled in the bottom bracket for mounting a cable guide. Sticking one of those in your frame would fix the issue. Mar 9, 2020 at 17:15
  • What material is your frame made of? Mar 9, 2020 at 20:27

2 Answers 2


Barring a drain hole somewhere, a drain hole allows air to move so equalizes pressure. A sealed system will create negative pressure with temperature changes and suck in water around moving parts. The bottom bracket or fork are the only other places a typical frame has holes that would allow water to escape.

Given these probably about as inconvenient to remove as the seat post, the only real option you have is a drain hole.

You could always upgrade :) to an external routed dropper so its possible to remove the post, or install a long enough dropper cable that you can pull the seat post, and either cable tie it in a loop after it exits the frame (I know, you are rolling your eyes right now.)

Question I have to wonder is where is the liter getting in.


Frame access points:

Chainstays typically have a vent hole you can use this for draining by tipping the bike and rotating to get the water to come out

Water bottle bosses open to the seat tube and down tube and can help with getting the frame to dry completely.

To help displacing the water, 90% isopropyl alcohol can be squirted into the frame and will mix with the water to flush it out quicker. Use a little and make multiple attempts to drain the water and alcohol mix. Any remaining alcohol will evaporate much faster than the water to help avoid rust.

Acetone is even more volatile and works great BUT it also attacks lots of synthetics so I'd avoid that.

IMO the most efficient method is to drill a small drain hole in the center of the bottom bracket shell and plug it with a short stainless sheet metal screw or for a more clean approach use a tap to thread the hole and use an M9 bolt or similar. Bottom brackets have had drain holes forever so I wouldn't be concerned with compromising the strength of the BB shell.

Once you sort out how to drain the water I'd suggest a serious look into where/how that much water is getting into the bike. There are lots of simple measures like sealing drain holes with electrical tape, lube around the seat post, etc. Unless of course the bike is being ridden through deep water in which case yeah you're going to get water through the bottom bracket and other sources.

  • 1
    There are those silicon-rubber collars that slip over the seatpost before it is put in place. Quite a lot of water ingress happens along the seatpost, especially if there is a slot at the top of the seat-tube (this mainly on steel frames).
    – Carel
    Mar 9, 2020 at 20:32

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