How to make an eternal log and how much firewood can be saved with it

The controlled supply of water vapor to the furnace prolongs the burning of firewood and increases the heat transfer from the flame to the brickwork or metal parts of the boiler. To achieve this effect, the “eternal log” device is used. If you have a grinder, a drill and electric welding, you can do it yourself, while receiving savings on firewood of about 15% and higher.


  • steel pipe d72 mm along the length of the furnace;

  • thick sheet metal for plugging the pipe;

  • steel corner or tire;

  • nut and bolt M16;

  • steel rod d 6-10 mm.

Making eternal log

First you need to cut the pipe along the length of the furnace. Ideally, it should be equal to commonly used firewood. From a thick sheet metal 2 circles of d72 mm are cut out and welded at the ends of the pipe.

To prevent the log from turning over, 2 legs are welded to its bottom. They can be made from a corner, fittings or tires.

A hole is drilled at the top of the workpiece with a 16 mm drill. A nut is joined and welded to it. The result is a filler neck. As a cover, an M16 bolt is used.

So that it can be twisted by hand, you can weld a piece of rod or reinforcement to the head.

At the top of the log, one row of holes is made with a 2 mm drill. The drilling step is 4 cm. Steam will come out through them in the future.

How it works

Through the neck, water is poured into the log, preferably hot. The lid-bolt is twisted, and the device is placed in the firebox with firewood. After the boiler is ignited, water from the eternal log begins to evaporate, affecting the combustion process.

What a saving

To evaluate the effectiveness of the eternal log, you can make a comparative experiment using the same amount of firewood. The first day, kindle a boiler with logs, measuring the temperature obtained and the duration of combustion, and on the second day, heat the stove without a device. In my case with the eternal log, burning with almost the same temperature lasted 15% longer. This is the saving on wood, allowing you to spend much less fuel over the winter.

Such a device really works, but it should not be used in stoves of the old type. Unburned water vapor will make soot sticky and lead to condensation. If a direct chimney comes out of the boiler, then the eternal log fits perfectly. In a long chimney with many channels from the device there will be more problems than good.