I just sent this e-mail to ThruNite since both of my T10's were not water-resistant out of the package! Here is what I told them:
"I would like to report a problem regarding waterproofing of both of my
Thrunite T10 lights. As you recall from our previous communication one
of my lights exhibited moisture under the lens. Today I took the time
to take both of my T10 lights and do a very simple waterproofing test.
The light with the moisture problem is my EDC while the other one is
brand new, I only keep it in case the first one is damaged and I need
a replacement. I was shocked to discover that the rubber o-ring at the
body of the light is NOT making proper contact. My test was to
submerge the lights in a glass of water, lens side up, with enough
water to cover approximately 1cm over the lens.
This is by no means a pressure test and a light that claims to be IPX8
should not even get moisture inside, otherwise the claim is false.
Immediately after I put the lights in the glass I noticed air bubbles
coming from the dividing line which meant that air was escaping and
water was getting inside! I removed the lights within 30 seconds as
the bubbles were getting less frequent. BOTH lights had small drops of
water on the inside of the battery tube and on the PCB. I assumed this
would be an o-ring problem so I replaced the o-rings with the ones
supplied as spares with the light. I did the test again and the
results were the same! This is a huge disappointment for a light that
claims to be ANSI-tested and has passed IPX8 water-resistance tests.
I then proceeded to clean and re-lubricate the threads and o-rings
with thick silicon grease, McNett brand made in the U.S.A. Both lights
have been under test for 15 minutes and NO air bubbles have escaped.
I hope that the problem was due to bad lubrication and not due to
faulty design, However, I have to note that the o-rings used in this
light are significantly smaller than the diameter of the threads. This
leads to stretching which in turn reduces the thickness of the o-ring
and makes the seal inefficient. I believe this is something you should
seriously consider, most people would expect a light that has passed
IPX8 testing to be water-resistant to at least 2m of water. This is
clearly not the case with both my lights."
What bothers me more than the possible lubricant issue, is the o-ring stretching and becoming thinner. Has anyone ever had a similar problem with lights with thin o-rings?