There is nothing more frustrating than failing a pre-flight vacuum test the day before an important dive. We suggest the following steps to help find that persistent leak:
- Mix a liquid soap solution in water (more soap than water) and fill into a small spray bottle (at least 1/3 full). Dishwashing liquid will do but avoid anti-bacterials
- Place a towel under the ROV and close all enclosure vents except the leaking enclosure. Make sure to protect the topside FathomX card from spray
- Using the brass fitting and tubing from the vacuum tester, connect the leaking enclosure’s vent to a bicycle hand pump (NOT electric)
- Carefully spray the leaking enclosure with the soap solution. We suggest starting with the rear end-cap and penetrators. If you aren’t able to find the leak there, repeat with the front end cap and flange edges.
- Gently pump air into the enclosure and look for bubbles. One or two pumps should be sufficient – too much pressure will cause the end caps to pop off. The bubbles will narrow down the location of the enclosure leak(s).
Possible causes could be a loose penetrator, a cut or broken o-ring, dirt or hair on the o-ring, not enough silicone, etc.