Heating alternatives...

To recap: the pod has built-in resistive heating pads in the bottom, with a temperature control unit. But Brian thinks these will wear out -- and having the system fail is bad, as the pipes will burst when the heating fails and the temperature drops, allowing the salt to come out of solution and expand. (The option I liked before, with a coil-around-tube solution doesn't actually exist in ready-to-go form. It's evolved into option (1) below.)

So, I need to look at other possible alternatives, at least as a backup. Here are the contenders.

1) Hot tub heater, pumping water through a thermocouple, in line with the existing filter/pump system. [Link] (Cannot use hot tub heater on salt water directly, as it will burn out the element rapidly.)
PRO: Excellent digital controls. Could also use it to potential provide control for the air pump, lights, etc.
CON: Substantial engineering challenges. Have to run both pumps together, always. Fairly expensive. It's noisy when the pumps run. Expensive ($1000+)

2) Hot tub heater, pumping water through stainless steel pipes that run directly through the water in the tub. [Link] (This is how Brian's tub is heated.)
PRO: Excellent digital controls. Same as above.
CON: Some engineering challenges. Means cutting 2-4 holes in the tank. It's noisy when the pumps run. Don't have to coordinate the two pump systems. ($1000+)

3) Water bed heaters, glued to bottom (outside) of tank. [Link]
PRO: Simple. Cheap. (~$150 for a pair)
CON: Probably poor temperature control -- would need to improve control system, very possibly. Some concern about getting good thermal coupling between heaters and water.

4) Submersible plastic heater, with built-in temperature control unit; typically used to heat baptismal fonts or koi ponds. [Link]
PRO: Simple. Moderate price. ($375)
CON: Means having a warm non-secured (though this could be solved) heating rod sitting in the bottom of the tank. Might need two elements for sufficient power.


(1) and (2) involve a lot of work, but should provide the long term best solution. (3) seem viable but crufty. (4) Seems most likely to work with least effort and moderate cost.

I'm leaning towards (4) as a way to be sure I have a good backup. Even if I eventually go with (1) or (2) , having a simple, reliable backup heater isn't a bad thing.


In terms of news... Brian has had a guy (Ted) work on this type of project before, and he's planning to come out Saturday to do ALL the plumbing work. It'll cost us something but at least it'll be forward progress! Hurrah!