The water used in espresso machines is easily the single most important factor for their longevity and functionality - and our machines are no exception. Using the wrong water can lead to scale buildup, causing heater failures which require sending the machine back to our Hong Kong factory for repair - failures we cannot cover under warranty.
The good news: our machines are designed to safely use reverse osmosis (RO), distilled water, which is actually the ideal water choice. With sufficiently soft water (under approximately 30ppm TDS) there is no need to ever descale, since no scale will build up in the machine.
This document provides specific water recommendations based on your water source, guidance on when descaling is necessary, and explains why our machines benefit from softer water than typical espresso machines.
The Basics
Using RO or distilled water affords us the following:
RO and distilled water are both widely available for purchase in much of the world. Many bottled waters use reverse osmosis or distillation - take a look at the label. Other options naturally include reverse osmosis systems (both countertop and under-counter systems exist), and countertop water distillers.
Another viable option is very soft bottled water (Volvic, Crystal Geyser bottled in California or South Carolina, or Poland Springs), in which case we would recommend annual descaling.
Practically speaking, we have yet to see heater failures due to scale on machines running water under 120ppm TDS, and water like this tends to be quite safe. The machine is intentionally designed to reject scale and deposit it harmlessly in the water reservoir, and the simple fact that water is moving through the heaters (rather than stagnant) during use makes it more difficult for scale to build up.
We recommend descaling once per year with a 5% citric acid solution if using water between 30-120ppm TDS. Please do not descale with anything other than citric acid, since we cannot guarantee that other descaling agents will not damage the machine's components. We cannot cover damage caused by other descaling agents under warranty.
The water you use in your espresso machine is, far and away, the most important factor that determines the longevity of the machine's components. We'd love to see your machine running for as long as possible without parts failing! With reverse osmosis or distilled water, you will be less likely to see parts failures and can use your machine without having to worry about scale buildup.
The Fine Print
Adding minerals to the coffee after brewing leads to essentially the same results in the cup as brewing with those minerals already present (if not a little better in many cases), allows us to use the ideal water in the DE1, and additionally allows us to use ions, such as chlorides, that really should not be in the water used in the machine. Additionally, this approach also allows you to more easily switch from making espresso to filter, with ideal waters for each, which many users find helpful. Resources exist on Diaspora to help you make these concentrates.
Deionization media, (such as that in ZeroWater pitchers) produces water that is interchangeable with RO or distilled water for our purposes, since the water is stripped of essentially all dissolved solids.
Tankless reverse osmosis systems can exacerbate a phenomenon called “TDS creep” where the first few hundred mL of water from the reverse osmosis membrane has a much higher TDS than what comes after (once the membrane has reached steady-state). If the machine is plumbed into a tankless system like this, it is, in some rare cases, conceivable for the water the machine uses to rise to a high enough TDS that periodic descaling would be advisable. However, if you opt for a tankless RO system, we would, on balance, recommend a system that compensates for the TDS creep, ensuring the output water has a more consistent TDS. This has the added benefit of making your water (and therefore the taste of your coffee) more consistent.
If you choose to remineralize water going into the machine, please do not use chlorides (such as calcium or magnesium chloride) to do so, as the chloride ions greatly increase the corrosion risk. The major factors increasing corrosion risk to the stainless steel inside the machine are chlorides in the water and significant acidity. Third Wave Water uses minerals that will not deposit limescale, and adds no chloride that would increase corrosion risk, however it is possible for TWW to cause buildup in the steam heater over time which requires descaling to remove. To avoid this, we will frequently recommend using TWW at 3/4 strength or less. If using TWW, we recommend descaling annually if using it at half strength, or twice a year if at full strength.
“Pavlis water” where deionized water is remineralized with potassium or sodium bicarbonate only, is safe to use in the machine at typical addition rates of approximately 80ppm KH. If using water with only sodium or potassium bicarbonate added, it may be prudent to periodically run the descale cycle using plain deionized water, in order to clear out the steam heater from the dissolved solids left behind as the heater evaporates water, however we are unaware of any cases where not doing this has lead to a heater failure. Running the descale cycle with plain deionized water is not a substitute for descaling when using waters containing calcium or magnesium.
Any tap water should be filtered before use in the machine. However, note that carbon block/media filters do not appreciably change how much your water will deposit scale, since they do not significantly affect the amount of dissolved calcium and magnesium. If using treated tap water, be mindful of the chloride content, since chloride greatly increases the corrosion risk to the machine. Ideally, keep chloride under 10ppm. Anion‑exchange softeners (used to reduce nitrate or tannins, or for dealkalization) can substantially increase chloride levels. Typical salt-based (or potassium chloride-based) water softeners do not significantly increase chloride levels in the water.
Above roughly 30ppm, the risk of scale deposition starts to increase to the point where we can't give blanket recommendations not to descale. Scale deposition will vary with the TDS of your water, the calcium (and magnesium) carbonate content, and the pH. The more alkaline (higher pH) your water is, the more likely it is to deposit scale in the machine. If you must use something besides reverse osmosis or distilled water, then we recommend looking up water reports for your water or getting it tested, so that you can calculate the Langelier Saturation Index (LSI) of your water, which describes the water's propensity to deposit scale.Here is a link to a calculator made by Barista Hustle which can help with this.
If the water being used in the machine will deposit scale (positive LSI), we recommend periodic descaling. Scale buildup can lead to heater failures which require the heater be completely replaced, which is a repair that necessitates the machine be sent back to the factory in Hong Kong for our staff to repair. Repairs on machines that have experienced failures caused by using water hard enough to deposit scale, and not adequately descaling, are unfortunately not something we can cover under the warranty, since that falls under“damage caused by you.”
Here are some general starting recommendations for how often to descale, based on the LSI of the water:
As a rule of thumb:
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