Some sauna heaters can include a water tank — a vessel heated by the stove that provides hot water for washing or rinsing — and some (usually electric) offer a built-in steamer that produces controlled steam for added humidity. A water tank is a traditional feature of many wood heaters, giving hot water without separate plumbing, while a steamer lets you add humidity in a managed way beyond throwing water on the stones (löyly). Neither is essential — löyly on the stones gives steam, and a bucket gives washing water — but they're useful conveniences. Choose them based on how you'll use the sauna, and follow the heater manufacturer's guidance for use and safety.
Beyond simply heating the room, some sauna heaters offer two useful extras: a water tank for hot washing water, and a steamer for controlled humidity. Neither is essential — the stones give you löyly, and a bucket gives you water — but both are conveniences worth understanding when choosing a heater. This guide explains what they do and whether you need them.
The water tank
A water tank is a vessel heated by the stove — commonly on or beside a wood heater — that provides hot water for washing or rinsing without separate plumbing or a water heater. It’s a traditional feature of many wood-burning saunas, using the heater’s warmth to give you warm water for cleaning up.
- Traditional on many wood heaters.
- Hot water without plumbing.
- A convenience, not an essential — a bucket and cold plunge cover the basics.
The steamer
A steamer — usually a feature on some electric heaters — produces steam in a controlled way to add humidity, beyond the burst you get from löyly:
- Lets you manage humidity more precisely.
- Suits those wanting a consistently more humid sauna.
- Optional, since löyly on the stones already provides steam.
Steamer vs löyly
| Löyly (on the stones) | Steamer | |
|---|---|---|
| How | Ladle water on hot stones | Managed steam system |
| Timing | Momentary, session by session | Continuous, controlled |
| Control | Hands-on, by you | Set humidity level |
Löyly is the traditional, hands-on, momentary way to add steam; a steamer offers consistent, controlled humidity as a heater feature. Both add humidity — many saunas rely on löyly alone.
Do you need either?
No — both are optional conveniences. A sauna works fully without them:
- Löyly provides steam.
- A bucket plus a cold plunge or rinse covers washing and cooling.
Decide on how you’ll use the sauna: if hot washing water or consistent humidity matter to you, these features are worth considering; otherwise, a standard heater is enough. See choosing a sauna heater.
Winter care
Common mistakes
- Assuming you need a tank or steamer — löyly and a bucket suffice.
- Leaving water in a tank or steamer to freeze in winter.
- Expecting a steamer on every heater — it’s a specific feature.
- Ignoring the manufacturer’s guidance for use and winter care.
Next steps
If you want hot washing water, look for a wood heater with a water tank; if you want controlled humidity, consider an electric heater with a steamer. Both are optional — löyly and a bucket cover the essentials. Weigh them when choosing a heater, and remember to drain water features before freezing weather.
Frequently asked questions
What is a sauna heater water tank for?
A sauna heater water tank is a vessel heated by the stove (commonly on or beside a wood heater) that provides hot water for washing or rinsing, without needing separate plumbing or a water heater. It's a traditional feature of many wood-burning saunas, using the heater's warmth to give you hot water for cleaning up during or after a session. It's a convenience rather than an essential — a bucket and a cold plunge cover the basics — but many people value having warm water on hand. Follow the heater's guidance for filling and use.
What is a sauna steamer?
A sauna steamer is a feature, usually on some electric heaters, that produces steam in a controlled way to add humidity to the sauna, beyond the burst of steam you get from throwing water on the hot stones (löyly). It lets you manage humidity more precisely, which some people prefer for a consistently more humid sauna experience. It's an optional extra, not a requirement, since löyly on the stones already provides steam. If controlled humidity appeals to you, a heater with a steamer offers it; otherwise, löyly does the job.
How is a steamer different from löyly?
Löyly is the burst of steam and heat from ladling water onto the hot sauna stones — momentary and controlled by you, session by session. A built-in steamer produces steam in a more managed, continuous way to maintain a chosen humidity level. So löyly is the traditional, hands-on way to add steam, while a steamer offers more consistent, controlled humidity as a heater feature. Both add humidity; the difference is that löyly is manual and momentary, while a steamer is a managed system. Many saunas rely on löyly alone.
Do I need a water tank or steamer on my sauna heater?
No — both are optional conveniences, not essentials. Löyly on the hot stones provides steam, and a bucket plus a cold plunge or simple rinse covers washing and cooling, so a sauna works fully without either feature. A water tank adds hot water without plumbing, and a steamer adds controlled humidity, which some people value. Decide based on how you'll use the sauna: if hot washing water or consistent humidity matter to you, these features are worth considering; otherwise, a standard heater is enough.
Are water tanks common on wood sauna heaters?
Yes — a water tank is a traditional feature of many wood-burning sauna heaters, using the stove's heat to warm water for washing or rinsing without separate plumbing. It's a practical, long-standing part of wood sauna culture, especially where there's no plumbed hot water. Not every wood heater has one, and electric heaters more often use a steamer for humidity rather than a water tank, so check the specific heater. If a wood heater with a water tank appeals, look for that feature when choosing. See our wood-burning heater guide.
Do water tanks and steamers need special care in winter?
They can — any water left in a tank or steamer in an unheated outdoor sauna could freeze in a cold climate, so you may need to drain or manage the water when the sauna isn't in use, following the manufacturer's guidance. This is part of winterizing a sauna and preventing water freezing. Because the specifics depend on the feature and heater, follow the manufacturer's instructions for winter care. Draining water from tanks, steamers and containers before freezing weather is a sensible general precaution. See our winter water guidance.
