Steam Generator Auto Flush and Auto-Drain Features

What Is Auto-Flush and Auto-Drain?

Auto-flush, also called auto-drain, is a feature on some steam generators that automatically drains and rinses the water tank after a steam bath. It removes water that has been heated, along with any dissolved minerals that have settled out as scale. The process is designed to keep the inside of the generator clean without requiring you to remember to do it yourself.

According to MrSteam, their AutoFlush system "automatically flushes the steam shower generator of sediment two hours after every steam bath." Similarly, Amerec offers an "ADK auto drain" option that automatically drains and flushes the generator after each use. Both manufacturers emphasize that this routine maintenance is key to a long-lasting unit.

Why Scale Builds Up in Steam Generators

Steam generators heat water to produce steam, and as water evaporates, minerals like calcium and magnesium remain behind, forming scale on the tank's interior and heating elements. This is especially problematic in areas with hard water. Amerec notes that "good water" is desirable "to protect the plumbing systems, including a steam generator, from the negative effects of hard water." Without intervention, scale can reduce heating efficiency, clog valves, and eventually lead to premature failure.

The buildup also affects steam quality. Residual scale and sediment can be carried into the steam, potentially making it less pure. An auto-flush system removes this residue before it accumulates, helping to keep the steam clean and the generator working at its best.

How Auto-Drain and Auto-Flush Systems Work

The mechanics are straightforward. After a steam session ends, a timer or control board triggers a drain cycle. The generator releases the remaining water through a drain line, and fresh water is used to rinse the tank. MrSteam's AutoFlush waits two hours after the bath, likely to allow components to cool and to prevent thermal shock.

For a successful auto-drain, Amerec recommends connecting a cold water supply so that "the optional automatic drain cycle can cool water in the tank before flushing." A drain line must also be installed to carry the flushed water away. This is part of the standard installation for a steam generator, so ask your installer to include it even if you choose a model without auto-drain, so you can add the feature later if needed.

Who Benefits Most From Auto-Flush

Auto-flush is not essential for every user, but it makes a significant difference in several situations.

Consider this feature if you:

• Use your steam shower multiple times a day or daily, because the more often the generator runs, the more scale accumulates.
• Live in an area with hard water, since mineral deposits build up faster and can be more aggressive.
• Prefer a low-maintenance routine and want to skip the monthly manual flush that Amerec describes.
• Plan to rent out a property or have a vacation home where you cannot perform regular maintenance.
• Want to extend the life of your generator, as Amerec states a properly maintained unit can last at least 10 years.

What to Look For in a Steam Generator

When shopping for a steam generator, check the specifications for an auto-drain or auto-flush function. Manufacturers may call it by different names, such as "auto drain" or "Automatic Drain System." If the feature is optional, confirm that the model you like can accept the add-on kit.

Beyond auto-drain, consider a water treatment solution. Amerec suggests that a whole-house water softener or a dedicated filter can "reduce scale build-up inside the generator water tank," which works alongside the flushing cycle. You can read more in our learn article on hard water and water softeners.

Also look for independent safety certification. Intertek explains that the ETL Listed mark is proof that a product has been tested and certified to safety standards by a Nationally Recognized Testing Laboratory. Choosing a certified generator helps ensure it meets electrical safety requirements.

For specific model comparisons, see our best steam generators for a shower guide and our Amerec and Mr. Steam roundups.

If Your Generator Lacks Auto-Flush

If your current generator doesn't have auto-drain, you'll need to manually flush it. Amerec advises that "your tank will need to be flushed monthly, or more often, depending on local water conditions." This means draining the tank and rinsing it to remove sediment, then refilling it before the next use.

Create a maintenance reminder to stay on schedule. Pair this with a periodic descaling routine, which is covered in our guide on descaling steam generators. If your water is very hard, you might also install a water softener or use distilled water, though be aware that some manufacturers have recommendations for water quality (see distilled water).

What to Pick for Your Use

Questions

Does auto-flush use a lot of water?

The flushing cycle uses water to rinse the tank, but the exact amount varies by model. Amerec states that a residential generator consumes less than 2 gallons of water during 30 minutes of operation, which includes steam generation. Since steam generators require electricity, homeowners in areas prone to outages often also review backup power generators. The flush itself is a short rinse and does not add substantially to water use.

Can I install auto-drain on an existing generator?

Some manufacturers offer auto-drain as an add-on kit, as Amerec does with its ADK option. Check with the manufacturer to see if your model supports it. You'll need a drain line and a cold water supply near the generator.

How often should I manually flush without auto-drain?

Amerec recommends flushing the tank monthly, or more often if you have hard water or use the generator frequently. If you notice scale buildup, increase the frequency.

Will auto-flush completely eliminate scale?

Auto-flush removes accumulated sediment and scale, but it does not prevent scale from forming in the first place. Using a water softener or filtration system reduces the minerals that cause scale, so combining both approaches gives the best protection.

Is a drain line required for a steam generator?

Yes, for auto-drain you'll need a drain line to carry away the flushed water. Even without auto-drain, Amerec recommends installing a drain line so the generator can be drained and flushed regularly.