You know that maximum water level line on heaters?

[Arcteryx]

I've been told that it's OK to dunk the entire heater into the water...i.e. past the maximum water line, control dial... thought I'd check with you folks to see who does that...

[The Guy]

That min. water line has to be on there, I think it has something to do with the approvals of the heater. The package usually says submersible. Any heater experts out there can you confirm this My new visi-therm heater has a min water line on it, but it's completely submersible. Hey I asked the same question when I got a heater.

[gklaw]

I think there may indeed be such thing as max level. It is a CSA certification issue.

I submerge mine

But if I tell you you can submersed them, you may come back to sue me if you get electrocuted

There are also heaters that will eventually leak as well. What are the consequence will be case specific.

[BelieveInBlue]

I completely submerge all my heaters, as I make sure to get ones that have "fully submersible" on the packaging. I've not had any problems yet, save for the occasional angelfish spawning on them...

[Immus21]

I've never submerged a "fully submergeable" heater but would assume that it is safe. You could always sue the manufacturer if it did malfunction..... ;-)

[Ursus sapien]

there's a world of difference between 'minimum' water line and 'maximum' water line.

Submersible heaters are designed to be submersed, and will over heat otherwise. That line just indicates the minimum amount of heat that must be in the water. Non-submersible heaters aren't water proof where plastic meets glass; they leak, and short out. Go higher than that line and water will wick into the wiring.

The same holds true for nonsubmersible heater placement near air stones and hob out-puts, where bubbles splater the exposed parts.

[gklaw]

Non-submersible heaters aren't water proof where plastic meets glass; they leak, and short out. Go higher than that line and water will wick into the wiring.

That is the sound approach. That is why there is CSA. Use submersible heater only when you need to submerge. If there is a CSA stamp and there is a max identified, stick with that. The manufacturer put a max. level there because they cannot demonstrate to CSA that it is safe to submerge beyond that level.

[fuzzysocks]

I completely submerge all my heaters, as I make sure to get ones that have "fully submersible" on the packaging. I've not had any problems yet, save for the occasional angelfish spawning on them...

Don't worry, all of my angels have eventually figured out that heaters lead to poached eggs, though it helps if you have large java ferns in the tank. Give yourself three weeks of rushing home to feed brine shrimp and daily water changes, and you'll wish they'd go back to spawning on the heaters!

[BelieveInBlue]

I have java fern, aponogeton, a nice flat piece of rock, and amazon swords; they still prefer the heater, or the glass... =.=

[AdamsB]

If a heater Isn't covered sufficiently It can overheat. I learned this the hard way. Doing a 80% water change on a fishless breeding tank, while refilling i heard a huge cracking noise. Turned off the water to see what happened and discovered a line the whole way down the heater where it split from the cold water hitting the hot surface. From then on I learned to turn off heaters before water changes. Oh beginner mistakes.

But back to your original question. I've had submersible and non submersible. All of which i submersed. My understanding is they are like water proof watches. Some are good to splash water on, some are good to 30m, some are good to 150m. Submersible are robust and can be placed anywhere in the tank. Non submersible are best left with the dial close to the water line. I'm open to correction though