# How many leaks have been fixed on the ISS, roughly?

Leaks come in all sizes. Very small ones might be ignored or remain undetected, slightly faster ones might be identified and dispositioned; if they are slow and going to remain stable, they might not be repaired. Leaks that are faster-still, or that might be unstable however are likely to be fixed immediately.

The video below, found in Spaceflight Insider's How was the exact location of the recent ISS air leak found? shows clips of use of an ultrasonic leak detector aboard the ISS and at least one instance where it seems a leak was repaired.

After astronauts determined from which of the modules the leak is coming from, in this case the upper section of the Soyuz MS-09 spacecraft, they used a device called an ultrasonic leak detector (ULD) to find the precise location of the Soyuz spacecraft that was leaking atmosphere.

Question: Roughly how many leaks have been actively repaired (fixed) on the ISS?

If it's possible to answer, I'm also curious if the existence of any were initially discovered by ULD use, or if the leaks that were repaired were all first sought after a drop in pressure was recognized.

below: screenshot from a recent Roscosmos tweet of cosmonaut Sergey Prokopyev (presumably) talking about the lead detection and repair and showing an ULD? (I can't speak Russian, but presumably this is correct.) Translating the text using Google:

"Friends, I decided to shoot a video to answer your numerous comments and dispel rumors. Everything is calm on the ISS! "

• I've added the russia tag in hopes of getting this double-checked by someone who speaks Russian, thanks! – uhoh Sep 17 '18 at 6:56
• The ULD isn't brought out until a leak is confirmed; it's not routinely used to check the cabin. Leaks are found by pressure or dp/dt sensor trends.The only other "big" ISS leak I'm aware of was in the USOS at a window, IIRC because the crew had been using a piece of tubing as a handhold and loosened it. – Organic Marble Sep 17 '18 at 11:49
• @OrganicMarble that sounds exactly like what's shown in the video; a window with "handle-shaped" tube next to it. – uhoh Sep 17 '18 at 11:58
• Ah. I rarely watch videos in questions, and didn't this time. – Organic Marble Sep 17 '18 at 11:59
• does the toilet maintenance leak count? – JCRM Feb 12 at 10:35