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How our coil heats your tub

The thermosyphon effect

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Safety & best use: Welcome

What is the thermosyphon effect?

The thermosyphon effect is a natural circulation process where water moves due to temperature differences. Here's a simple breakdown:

  1. Heating Water:  When water is heated, it expands and becomes less dense.

  2. Rising Hot Water:  Because the hot water is less dense, it rises to the top.

  3. Cooling Water:  As the water cools down, it becomes denser.

  4. Sinking Cool Water:  The cooler, denser water sinks to the bottom.

  5. Cycle Repeats:  This creates a continuous circulation of water without the need for a pump.

When you correctly connect one of our coils to a full tub/tank of water, then light a fire inside the coil, the heat from the fire pulls water into the bottom of the coil through its lower tail. The fire heats that water and it rises up the coil. When the water gets to the top of the coil, it returns to the tub/tank a few degrees warmer. The cycle repeats over and over until your tub/tank gets to your desired temperature - at that stage you should bank the fire in your coil. 

If water does not seem to be flowing through your coil properly, the coil is spurting out very hot water, or you hear clunking/knocking sounds - the thermosyphon effect isn't working properly. Put out your fire immediately. See below for what can stop the thermosyphon effect from working. 


What would cause the thermosyphon effect not to work?

The thermosyphon effect works less well, sometimes not at all, in the following situations:

  • The coil isn't correctly connected to the tub/tank - such as the hose not having a snug fit to the coil, or connectors not being properly attached/fitted. This will allow air bubbles into the system.

  • The hose between the coil and the tub/tank is very long, especially if it sags. The thermosyphon effect powerful enough to drive the water much distance beyond the heated coil.

  • The coil is set on lower ground than the tub/tank, so the warm water has to travel significantly upward to return (for the same reason as above). 

The first issue can be addressed by carefully checking your set-up before and during first use, to minimise any chance of airleaks. The second two issues - if you cannot make the hose shorter or set the coil higher - can be rectified with a small electric water pump. 

Please see our Safety and Best Use page for more guidance on using our coils. 

Safety & best use: Text
Safety & best use: Text
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