TLDR; The strobe lives and seems to be working normally after cleaning it up.

 

Yesterday I was doing my second dive of the day when one of my HF-1 strobes made a little tiny pop and stopped working. The green indicator light was off and turning it off and on again did nothing. I was at about 80-85 feet at the time. I turned it off, folded it away, and used the remaining strobe for the rest of the dive.

 

I had set up my camera and strobes on Friday night, and they headed out early Saturday morning for two shore dives about a 90-minute drive away. The conditions were not great, and I didn't take many photos maybe 50. I lightly rinsed the camera and strobes at the dive site and then soaked it in the sink once I got home. I had another pair of boat dives planned Sunday morning, also a 90 minute drive. Since I had not taken many photos I decided to leave the entire rig, camera and strobes alone and dive it again without opening or charging anything. I did a few test shots and packed it in the car. The first dive all worked normally and during the second dive both strobes worked until the Pop.

 

After I got home, I soaked and dried the entire rig and then went to see what was going on with the dead strobe. Had the batteries died suddenly, was the strobe broken? It didn't seem likely to me that it might had flooded. As such, I was a bit surprised to see moisture and a little black goo in the battery compartment. It made another little pop when opened, releasing pressure. There was NOT a lot of water in it. It was not fully flooded, just a bit wet. The batteries and strobes electrical contact showed some black goo and corrosion on the positive terminal at the bottom of the compartment. I dumped out the batteries as set them aside wrapped in paper towels. (they went to a can outside the house) I took the strobe and rinsed it repeatedly under the sink and scrubbed the battery compartment with a toothbrush. My handy electric blower dried it out quickly. I wrapped some sandpaper on the end of a chopstick and cleaned up the corroded Pos+ terminal at the bottom of the compartment.

 

I went to the manual and confirmed my recollection that the battery compartment is sealed from the rest of the strobe. The manual says "maybe" the strobe will survive a flood, and that unless it starts acting erratically you can keep on using it. After allowing it to continue to dry overnight, I loaded fresh batteries this morning and the strobe seems to be working correctly 100%. I'll dive it in a few days to confirm further, but the good news is that it seems to live up to the sealed compartment promise of the manual.

 

I really don't know what caused the flood. I am very meticulous in cleaning and lightly lubricating the orings and sealing surfaces with tribolube with each battery change. There was no hair or debris in the seal when I opened it. No cracks in the case or cap that I can detect. I removed the orings and cleaned the cap and groves carefully with a toothbrush and lint free laboratory wipe. The orings seem to be in good shape so I cleaned those too and put them in spares. I swapped in the spare set of orings that Backscatter provided with the HF-1 on both strobes. 

 

I didn't take any photos of the flood, but it was not very dramatic in any case. Just a touch of goo and corrosion. It just goes to show that every strobe or o-ring sealed device is never 100% foolproof and the best we can do is take care. Have a spare on hand if you can't afford to be down a strobe on a big trip. I have a couple of big trips coming up in April and May, so I'll be bringing at least 1 spare strobe and a few extra batteries!

Sorry to hear about the flood, but good the strobe appeared to survive.  I can see a maybe 3 possible leak sources, the general integrity of the cap,  the pressure relief valve in the cap and the o-rings themselves.

 

This strobe has an additional o-ring sometimes called a sand seal that the strobe cap contacts when installed.  I have one of these on my INON torch and my experience is there is no water entry past that o-ring, so that I don't get sand/grit on the o-rings and there are never any water droplets.  My INON Z240 strobes always have water drops on the o-rings in contrast.  Did you happen to check for water droplets on your o-rings?

 

For the other two entry points, I'm wondering if it might be worthwhile to get a new cap as a precaution? 

We'll see what happens when I dive it again this week. There is usually some water under the cap, but I don't know if the orings are wet. Perhaps the first one is, but I could not say for sure. 

 

I know there is an overpressure valve, I assume that is the metal disk as the center of the cap. It would be interesting to know how to test that independently.

On 4/7/2025 at 10:55 PM, Dave_Hicks said:

moisture and a little black goo in the battery compartment

Are you sure it was water intrusion from the outside? I've had batteries leak electrolyte inside my strobe - granted, those were NiMH AAs, but Li-Ion cells can do it as well.

Your story reminds me of one from a few months ago involving Retra. Diving on more than one day without opening and re-sealing. What can happen? One can only speculate. I have done multiple dives many times without changing batteries in my strobes within a day but not with a time gap of an overnight. I have for the camera housing (two days diving (as well as stream shooting) without recharging or removing cards).

Edited April 9Apr 9 by Tom Kline

Maybe it is worth to take the strobe  UW, for the first dive after the leak, without batteries and some paper towels inside...

(In case the leak is via the pressure relieve valve, it will be almost impossible to detect this by inspection)

7 hours ago, Tom Kline said:

Your story reminds me of one from a few months ago involving Retra. Diving on more than one day without opening and re-sealing. What can happen? One can only speculate. I have done multiple dives many times without changing batteries in my strobes within a day but not with a time gap of an overnight. I have for the camera housing (two days diving (as well as stream shooting) without recharging or removing cards).

Yes, i thought about that. Could a build up of pressure in the compartment cause the issue? Perhaps only if the batteries were the root cause and not an external flood.

7 hours ago, Architeuthis said:

Maybe it is worth to take the strobe  UW, for the first dive after the leak, without batteries and some paper towels inside...

(In case the leak is via the pressure relieve valve, it will be almost impossible to detect this by inspection)

Probably a good idea.

it is interesting how relatively frequently it seems that strobe floods occur when they have remained sealed for X amount of time after diving, and then diving again. The only strobes I've ever flooded happened this way and I recall several other accounts both here and on we**ixel that were in the same vein

4 minutes ago, MatthewSullivan said:

it is interesting how relatively frequently it seems that strobe floods occur when they have remained sealed for X amount of time after diving, and then diving again. The only strobes I've ever flooded happened this way and I recall several other accounts both here and on we**ixel that were in the same vein

I guess we need to add "burp your strobe" to the best practices of Underwater Photography. 🙂 🫧

I got seawater into an old Sea&sea strobe once - never touched any of those Orings before. It was after a few dives, sort of half-way during the vacation. I think the Orings that sealed the strobe itself were simply showing their age. (For an HF1 that is simply impossible at this point, though- too recent.) But when I finally did take it apart, I couldn‘t find any obvious source of the leak. 

 

For the record: The batteries had stayed dry, since the compartment is sealed… 

I did not want to speculate above but one possibility is gas expansion in the battery compartment pushing the o-ring in the wrong direction. BTW when I take a pressure reading of my housing using the Backscatter model housing sucker part (there is a gauge on it), the vacuum reading tends be lower (!) after use in local water (local mean water temp measured by a graduate student is 5°C). Housing is still cold; it takes hours to warm up at room temp.

Edited April 9Apr 9 by Tom Kline

3 hours ago, Tom Kline said:

I did not want to speculate above but one possibility is gas expansion in the battery compartment pushing the o-ring in the wrong direction. BTW when I take a pressure reading of my housing using the Backscatter model housing sucker part (there is a gauge on it), the vacuum reading tends be lower (!) after use in local water (local mean water temp measured by a graduate student is 5°C). Housing is still cold; it takes hours to warm up at room temp.

 

Whether or not an o-ring can withstand reverse pressure depends upon the design of the o-ring groove.  A surface o-ring like used in Ikelite and the Nauticam housings  with removable backs cannot as they rely upon the external pressure pushing the housing back into contact with the o-ring.  A piston o-ring such as INON caps or the HF-1 should be fine

 

Lubrication can also be an issue on clamshell and piston style o-rings.  The o-ring needs to be able to slide back and forth in its groove to press up against the sealing surfaces and form the seal.  If the o-ring hangs up up it might prevent the seal from forming.  I note with my Z-240 strobes I apply a very thin layer of  lube to the cap inside surface and it screws on very easily.  When I come to remove the the cap it is often quite tight, like as if the lubricant has washed away.  If you had internal pressure the o-ring would need to move.  Internal pressure is relative - you could have higher internal pressure from taking your strobe to a higher altitude.  Having said that I often leave the batteries in for extended periods after a dive particularly if I only do one dive.   So far I've been fine.

Perhaps @MatthewSullivan is onto something.

I had an HF-1 flood 2 weeks ago in Anilao. The strobe worked the entire dive and I left the batteries in overnight as I had not taken many shots. I turned the strobe on in the morning with no power. Opened it up and found some salt water and corroded batteries. Rinsed with fresh water, dried, rubbing alcohol, dried. Left it a day to sit. Next day it powered up and continued working for another 10 days, but started to fail after that. It would power up at the surface, but then at depth, it would not power on. I tested again on the surface and it powered on.

FYI: I contacted Backscatter, and they will repair the flooded strobe and replace the battery cap for $235. Strobe is now out for repair.

11 hours ago, JayceeB said:

Perhaps @MatthewSullivan is onto something.

I had an HF-1 flood 2 weeks ago in Anilao. The strobe worked the entire dive and I left the batteries in overnight as I had not taken many shots. I turned the strobe on in the morning with no power. Opened it up and found some salt water and corroded batteries. Rinsed with fresh water, dried, rubbing alcohol, dried. Left it a day to sit. Next day it powered up and continued working for another 10 days, but started to fail after that. It would power up at the surface, but then at depth, it would not power on. I tested again on the surface and it powered on.

FYI: I contacted Backscatter, and they will repair the flooded strobe and replace the battery cap for $235. Strobe is now out for repair.

You made some nice pictures at Anilao. Sad to hear about the strobe.

It would be interesting to compile all of these reports to look for common threads. I can see no reason why a strobe would leak after some period sitting sealed up with the batteries inside after working on the first dive. O-rings are not that complicated they should just work if they are installed without any grit or hairs present. Pressuring, de-pressuring and re-pressuring should make no difference, we do this all the time to the control o-rings in housings and probably quite often to port o-rings, when we leave the same port in place for multiple dive days.

There are several different designs of o-ring installations including a surface groove with a flat plate sealing against it and various variations of piston mounts including screw on caps and variations of push and turn. Each have their own risks, for example it is possibly more likely for a surface o-ring to leak via a hair laying across the ring, especially if a vacuum is not used to seat the plate. Is one type more susceptible than others?

O-rings whether they are installed in strobes or camera housings or torches should behave the same way. The only difference these days is that strobes don't have vacuum systems, while a great many housings sold today have one.

One possibility is if it's a small leak with only a few drops it may take time to kill the batteries. Quite possibly the o-ring leaked and the batteries kept going but after sitting for hours to days the water has worked its way in and done the damage. As the strobe was not opened after the dive it is not possible to prove or disprove this. Maybe moving the strobe around again after the time it was sitting is enough to get the water to move somewhere it can do damage, or the damage is minor but accelerates when the batteries are loaded?

19 hours ago, JayceeB said:

FYI: I contacted Backscatter, and they will repair the flooded strobe and replace the battery cap for $235. Strobe is now out for repair.

What is the reason for replacing the battery cap? Corrosion or a leaking overpressure valve?

1 hour ago, Architeuthis said:

What is the reason for replacing the battery cap? Corrosion or a leaking overpressure valve?

if the over pressure valve operates (lets expanding gas out) it will leak after so the cap needs to be replaced.

2 hours ago, Architeuthis said:

What is the reason for replacing the battery cap? Corrosion or a leaking overpressure valve?

I'm not positive on this one. I thought it was due to the risk of corrosion, but @cerich 's response makes sense too. I can say that after the leak and cleaning out the strobe and drying it, that the battery cap was still functional for another 10 days.

From a clear non-expert perspective: it is often recommended to leave the gear „open“ during air travel, presumably because the reverse pressure during flight may dislodge O-rings (?). Is this similar to surfacing at the end of the dive and then diving gain, or is the „travel-without-Oring“ advice overly cautious?

This has probably filled megabytes of forum threads already, so feel free to pm and enlight me.

9 hours ago, Klaus said:

From a clear non-expert perspective: it is often recommended to leave the gear „open“ during air travel, presumably because the reverse pressure during flight may dislodge O-rings (?). Is this similar to surfacing at the end of the dive and then diving gain, or is the „travel-without-Oring“ advice overly cautious?

This has probably filled megabytes of forum threads already, so feel free to pm and enlight me.

Reverse pressure won't impact most o-rings. Piston seal o-rings seal equally well both ways, a surface o-ring is generally not so good at reverse pressure, THis is the type which can trap a vacuum in a housing when taken on a flight, particularly if the clamps are not super tight. The force on the flat back plate is quite high and can cause it to lift and let out the internal pressure. When the plane descends it's like taking it for a shallow dive and it will trap the vacuum.

See the diagram on this page:

https://www.applerubber.com/seal-design-guide/oring-basics/dimensional-considerations/

The top one, the face seal may not do reverse pressure as well depending on clamping force applied, typically used on some housing backs for example which may have only 2-3 clamps around the perimeter. The other two seal both ways.

I'm curious about the rate of o-ring failure in housings equipped with vacuums. Certainly it makes good sense. As I think through the process of putting a vacuum into play - the pre-dive checkout - maybe the true value is noting errors during that process which prevents issues during the dive. After the check perhaps the vacuum isn't necessary.

The other thing that the vacuum does is to "load" the orings. This was critical in older housings like Ikelite with their original port clip system. They were kept sealed largely by water pressure compressing the port to the housing. In a dunk tank the slightest bump could make them leak. Today most housings use a mechanical latch to apply that initial load, but water pressure still magnifies it for a better seal.

11 hours ago, Dave_Hicks said:

The other thing that the vacuum does is to "load" the orings. This was critical in older housings like Ikelite with their original port clip system. They were kept sealed largely by water pressure compressing the port to the housing. In a dunk tank the slightest bump could make them leak. Today most housings use a mechanical latch to apply that initial load, but water pressure still magnifies it for a better seal.

Agree, this applies to every o-ring in the housing - pre-loading them helps prevent leaks on the surface. Even housings like the Nauticam only have two clip points and the clamping force is greater closest to the clamps. They rely on the stiffness of the housing back to evenly apply pressure all over the o-ring - probably a big benefit is the two locking pins which resist the housing back moving sideways. That's why flanges in pipe systems uses multiple symmetrical bolts. Housings are different in that they seal against external pressure, but getting even pressure on the o-ring is still important. Once UW the pressure is totally even but not so in the air unless you have a vacuum pulled.

It's not as bad as the old external clip housing like ikelite, but probably still not as good as the clam shell style backs many housing use.

I had the same issue before 2 weeks, let it closed overnight, and next day when I opened it, there was a little water inside. Luckily it worked after drying. I did not found any problem on o-ring or elsewhere. I changed the almost new o-ring without really thinking that this was the issue :-(.