Maintaining 93.5 degrees.

A goal with the float tank is to have the water at skin temperature, about 93.5 degrees F. This way, the body doesn't register the contact with the water -- it's a neutral experience.

But... how do you keep the water hot in a float tank? Well, it's a lot like a hot tub, except with really salty water. Apparently, and I haven't fully researched this, the standard big-resistor-with-water-flowing-over-it-inside-a-pipe approach doesn't work well for float tanks because the salt induces a whole lot of corrosion. You need a heating element and a controller.

The LilyPad comes with a bunch of resistive heating elements mounted in the bottom of the tank, along with a suitable (if rather old-skool) temperature controller. The issue is, according to Brian that 1) the resistive elements (think: heating pad or electric blanket) will eventually wear out, and they are hard to replace and 2) you don't want to be sitting in all those electric fields. I'm not convinced at all about #2, but I hear #1. The solution is to go with a pump-based heater, like a hot tub has. Basically, a length of tube which acts as a heat transfer device.

Corrosion, however, makes this a problem. Brian spoke with a representative from Balboa, a hot tub equipment manufacturer, who thought about the conductivity of the water and concluded the element might last a couple weeks with the highly saline salt water flowing through it. It has something to do with the conductivity of the water and the extra corrosive properties that such water has when flowing past an electric field. I can beleive that.

So: what do other tanks do? They use resistive elements in the floor. Why don't I just use the system I have? Well, it might burn out. And that would suck. Then why not put in a standard hot tub element. Well, it makes noise - the pump has to be on - and, it'll corrode too fast. You'd like to have a perfectly quiet float, right?

The solution, I hear you cry, is, I think, this: get a heating element where the hot material COILS around the outside of a stainless steel tube (vs. being submerged in it) and use that as the primary heater for the tank. But, when in the tank (see note below), use the existing resistive pads. This should extend the life of the pads dramatically, while allowing a quiet float on a separate control system. These exist and can be purchased. (Fabricating new objects with clever theromdynamic properties is to be avoided.)

Brian's tank has a whole separate heating system, where regular water is pumped through stainless steel tubes which pass through the main body of water, acting as a heat exchanger. Great solution, but requires a lot of changes to the tank.

My plan, at this point, is to add a coiled-around-the-stainless-tube heat exchanger, put inline with the main filter circulation pump, and to turn this off and use the pads for heat control when in the tub WHEN TRYING TO MEDITATE and remain conscious. If trying to sleep, no reason not to use the pump -- I'm a sound sleeper. This will doubtless cause some control and UI problems later, but such is life. And I guess I'm not that concerned about harm from small electric fields.

I think this gives me the best of all words, save for some loss of efficiency in coil-heating vs resister-in-pipe heating -- quiet floating, long lifetime for the existing resistive pads, and relatively few changes to the existing setup.

We shall see.