Historically, floatation tanks have used active heating. When a floatation tank is actively heated, heaters will heat the water if the temperature of the water deviates below the target temperature (of 93.5 deg F) during the float session. Even today, most floatation tanks use active heating.

However, around 15 years ago, we had a great yahoo group called “Float Talk” created by Frank Rodriguez that had many industry professionals on it. Tim Strudwick developed and announced his i-sopod tank to us on that group. I was shocked to learn that the water was only heated *between* float sessions, never while the floater was in the water. This was the first instance of passive heating that I encountered.

I thought Tim’s tank was the only such tank, but Dreampod also makes tanks with passive heating.

So we have 2 tanks that cost 5 figures designed for heavy professional use that use passive heating. Let’s look at the pros and cons of passive heating.

Pros

1. safer? I never understood how water could be heated without the possibility of electrocution. sure, you can put a GFCI shockbuster on the heater but what if the shockbuster is busted?
2. less electromagnetic interference – Tim mentioned that his clients could tell the difference between a tank that had electrical heating going on during the float session and greatly appreciated the absence of such electrical interference in his tank. Furthermore, in “The Deep Self”, Steven Conger eloquently states “… the wiring pattern creates a slight purely electrostatic field… a few persons are sensitive enough to detect when this is grounded: insulate the floor around the tank to avoid this effect.”
3. Easier to implement – this only applies to DIY tanks. The passive heating systems of the dreampod and i-so-pod tanks involve state-of-the art carpentry. However, for people with less-than-elite carpentry skills, one can manually place and remove water heaters and do so with the confidence that it supplies a quality float session. The Black Beauty DIY tank and the Ragtop DIY Tank both use passive heating in this manual fashion.

Cons

1. Extremely long sessions will eventually have temperature issues. If you want to sleep in a tank overnight or do a weekend intensive, the water will eventually become cold and you will interrupt your extended float session concerning yourself with heating. Tim Strudwick made it clear that for the 1st hour of a float you are radiating body heat. But eventually the amount of heat from the body will be less. At this point, unless the room is heated to 94 deg F the water will become cold.