Sauna Heater Stones: How Often Should They Be Replaced?

Replacing sauna heater stones is often an overlooked maintenance task, but it is crucial for ensuring the reliability of your sauna and the best quality of steam. The heat quality and heating efficiency of the sauna heavily depend on the condition of the stones. Worn and cracked stones can hinder air circulation and heat unevenly. The replacement frequency for both electric and wood-fired sauna heater stones depends largely on the frequency of use. Let’s take a closer look at the recommendations for replacing heater stones.

Replacing Stones in Electric Sauna Heaters

For electric sauna heaters, the frequency of stone replacement is typically outlined in the manufacturer’s instructions, but the general recommendation is to replace the stones at least once a year. If the sauna heater is used more frequently—such as in commercial saunas or rental properties—the stones should be replaced every six months.

The stones in electric heaters are directly heated by the heating elements, which can cause them to degrade faster. Cracked or worn stones increase air resistance, putting extra stress on the heating elements and potentially shortening their lifespan. Therefore, regular stone replacement is important not only for energy efficiency but also to extend the heater’s lifespan.

Recommendation:

Regular home use: Replace stones once a year.
Intensive use (e.g., commercial or public saunas): Replace stones every six months.

Replacing Stones in Wood-Fired Sauna Heaters

In wood-fired heaters, the frequency of stone replacement is more flexible since the stones are naturally heated and cool down more gradually. However, the lifespan of the stones still depends on the frequency of use and how often water is poured on them. The general recommendation is to inspect the stones regularly and replace them at the first signs of wear or cracking—usually every 1–2 years.

In wood-fired saunas, the upper stones wear out faster as they are exposed to water more frequently. The lower stones, however, endure higher heat and maintain their shape better. As a result, it may be sufficient to replace only the upper layer while leaving the lower stones intact.

Recommendation:

Regular home use: Check stone condition annually and replace every 1–2 years.
Intensive use (e.g., daily heating): Replace stones at least once a year, or more frequently if needed.

Signs That Heater Stones Need Replacement

In addition to the recommended intervals, pay attention to the following signs that indicate the need for stone replacement:

Cracking and wear: Stones are cracked or have significantly reduced in size.
Uneven heating: Steam quality is inconsistent, and the heater is no longer performing at full capacity.
Reduced air circulation: Blocked airflow between stones leads to increased strain on the heater and higher energy consumption.

The Importance of Choosing the Right Stones

The choice of stones is also important, and it’s best to opt for stones specifically designed for sauna heaters. High-quality stones withstand high temperatures better and have a longer lifespan, reducing the need for frequent replacements. For instance, olivine diabase and gabbro-diabase are durable materials that retain their properties for a long time. After replacing the stones, rinse them before use to remove dust and debris that could clog the heater’s air gaps.

How to prepare heater stones for use?

Before using heater stones, it is essential to prepare them thoroughly to ensure efficient performance and prolong the heater’s lifespan. First, rinse the stones with clean water to remove dust and loose particles that could damage the heater or produce unpleasant odors during heating. Then, sort the stones by size—place larger stones at the bottom layer and smaller stones at the top to ensure even airflow and better heating. Make sure the stones are tightly packed but not too compressed, as overly compacted stones can hinder efficient heating.

Pro Tip: Before regular use, heat the stones to sauna temperature once and allow them to cool gradually without pouring water on them. This process prepares the stones for the first steam sessions.

How to Arrange Heater Stones in the Heater?

Watch the VIDEO

Bottom Layer – Larger Stones: Place larger stones at the bottom of the heater to help retain heat and provide a stable foundation. Ensure the stones do not press against the heating elements to avoid damage.
Upper Layers – Smaller Stones: Use smaller stones for the upper layers, which helps warm the air in the sauna more quickly and evenly.
Ensure Airflow: Do not pack the stones too tightly. Leave space between them to allow for proper air circulation, ensuring more efficient heating and avoiding overheating.
Top Layer: Make sure the top layer is even, allowing water to spread evenly over the stones for consistent steam quality.
But Sauna Stones Are Useless Without a Heater

For an elegant and efficient solution, consider the HUUM HIVE Mini 9kW electric heater, made in Estonia from high-quality stainless steel. It holds up to 170 kg of stones, ensuring long-lasting and luxurious steam. Why choose HUUM? Watch the video to find out!

Choose the right sauna stones here.