Coating a heater

[apastuszak]

When you use friend Google to look up information about about aquarium heaters, there isn't a single major brand that doesn't have a failure story. Heaters with glass tubes have at least one story where the glass tube cracked and the fish got electrocuted.

So, I a wondering now....

Has anyone ever cover a glass tube submersible heater in pasti-dip, or some rubber coating, so that, if the glass cracks, everything stays together and fish (and owner) don't get electrocuted? I understand the challenges of making sure the the temperature control gauge still turns, the temperature setting is visible and you can see the on/off light. But it would be interesting to see if someone had pulled it off.

 

[Wild West]

Back in the day I had almost 30 tanks, I used black "shatterproof" submersibles in every single one. I never had one fail. I have looked for them now that I am back in the hobby after a long time, but yikes they are more expensive than I remember. On the other hand, probably worth the $$ for a reliable non-glass heater.

 

[Narwhal72]

If the glass cracks water is still going to penetrate. Even if it stays together. No real advantage there.

Rubber is going to act like an insulator which prevents the heat from transferring to the water. This ends up making the interior of the heater a lot hotter than it should be.

All glass heaters are made with borosilicate glass. Same as Pyrex. They are made for high heat applications and transfer heat well. Cracking tends to happen either from damage (drops, impacts,etc...) or (far more common) sudden changes in temperature. The most common cause of heater failure is forgetting to unplug it during a water change, causing the heating element to become exposed to air and get extremely hot, then refilling with cool water. This sudden change will often cause the glass to crack.

 

[apastuszak]

Sadly, in the US, Pyrex is now made of soda lime glass. I don't use Pyrex any more.

 

[Rbishop]

You might try shielding it with a guard, but that won't cure the most often failure issues as Narwhal noted, of lowering level on a water change. I prefer titanium tubed ones, but even they have failure rates.

 

[fishorama]

Yeah, I was going to suggest titanium heaters but you can't see any condensation inside...but again, I haven't gone that far...I've never tried them. But I still might say a controller w/1 heater might work better...if an investment for safety vs 2 heaters of any kind.

My big concern is with overheating not a non-working heater, IMO+E fish can stand low temps much better than cooking.

 

[apastuszak]

I've been lucky. Been in the hobby now since 4th grade and have never had a heater cook my fish. Have had plenty of them stop heating.

But I do think a controller is a good idea. But even a controller can fail.

 

[tanker]

Why are you worried about the glass cracking? It will not crack by itself. The only way a glass heater would crack is
1) If it is attacked (like by an Oscar).
2) We pour cold water on a hot heats
3) We drop it when removing it from a tank.

 

[Rbishop]

or, if with a low water level the heater still on cracks.....

bumped by hardscape movement on a cleaning/rearrangement...

thin glass and heat stress from age.....

 

[pbeemer]

Sadly, in the US, Pyrex is now made of soda lime glass. I don't use Pyrex any more.

umm, if it's branded "pyrex" it's supposed to be borosilicate glass, not soda lime -- at least that is the limitation of the US trademark. corning's web site still says that it is borosilicate

to address the OP's question, i agree with comments above that coating the heater with rubber, while toughening it relative to mechanical and thermal shock, would substantially reduce the heat transfer. to get the same amount of heat through the coated walls, the insides would have to get at least twice as hot (estimating doubling the thermal resistance, which i think is very conservative); the innards of the heater are never going to be able to stand that and something catastrophic should happen pretty soon after it's plugged in.