Skimmer turned into a geyser?!

Well the other night, don't know what I did wrong but as I was adding a few gallons of water into my sump(while return pump and skimmer were on), once I was done all seemed fine and about a minute later out of nowhere my skimmer fills up with water and starts overflowing like a geyser! All of this happened within like 10 seconds and there was already about half and inch of water in the stand around the sump.
This is a dumb question, but should I have done this with the skimmer turned off or was the level of water too high for this malfunction?
Probably something simple like that, but I can imagine if I walked out of the room for a while and came back to see my whole room flooded.
POS skimmer or human error?!

Skimmer: Vertex IN180

 

From what I have seen, FW doesn't bubble the same as SW. The bubbles are usually much bigger and even with a needle wheel they didn't aerate the same. Were you adding the FW next to the skimmer? could have sucked in a big shot of FW water which might have messed with the water/air flow through the skimmer. I don't shut off the skimmer or return when I do my daily top off. I just make sure not to add too much FW at once. My sump has 3 chambers and I always top off in the return chamber which is the last and where I see my water loss.

 

What type of skimmer?

Skimmers that inject air into the chamber through the pump that also pumps water in (the majority of skimmers out there to this) can flood if the airline gets obstructed in some way. What happens here is that instead of pumping part air/part water they pump a higher volume of water which will fill your skimmer up and likely cause it to overflow.

Is it possible something got into the airline?

 

If the skimmer in question is an "in-sump" model, what you're experiencing is water depth variation. Many skimmers are sensitive to the depth of water they sit in due to the fact that the "base" water level will rise and fall in the skimmer body.

The best thing to do if you have a "picky" skimmer is adjust the level down before you fill the sump, then re-tweak it in once the sump is topped up.

 

I have been having a similar problem. My skimmer is in a constant water level in the sump but changes and does not want to dial in. After looking at this post I had changed where the ATO water is being added. Think you identified my issue as well. Thanks.

 

What kind of water? If its tap water with a conditioner, skimmers go bonkers. If its good RO/DI it should not have much of an effect, usually mine slows down when larger amounts of RO/DI are added.

 

If it's an insump skimmer, it's most likely caused the change in the level in your sump. My insump skimmer sometimes does the same thing but it's usually caused by calcium buildup in the venturi valve that sucks in air, changing the air/water mixture and filling up the skimmer body which then overflows into the cup causing that to overflow....but in my case it all goes back into the sump.