Been thinking about using distilled water, just to fill up the steam boiler in my HX machine. I would NOT use distilled water for brewing.

Any reason not to take this approach?

Why would you want to ..
How would you not use the water to brew with ?

The auto fill sensor requires some minerals in the water to function correctly. If you use distilled water, it will not register when it's full, and it will overfill the boiler. Don't do it.

Mrboots2u wrote:Why would you want to ..
How would you not use the water to brew with ?

Reason would be to prevent scale.

I would fill the boiler from the reservoir with the distilled water, then refill reservoir and use different water for brewing. The distilled water would remain in the boiler for steaming. I don't use the hot water tap so it would remain in there for quite a while, with the occasional auto fill. Eventually I would replace the water again.

Beezer wrote:The auto fill sensor requires some minerals in the water to function correctly. If you use distilled water, it will not register when it's full, and it will overfill the boiler. Don't do it.

Good point. I would need to add a bit of tap water so this would still work.

That's what I did with the Elektra Semiautomatica. Since its steam boiler is manually filled, I waited until the sight glass indicated the water level was below halfway and filled the reservoir with distilled water. To avoid leeching, I used regular water from time-to-time to refill the steam boiler. Since I don't make many cappuccinos, the steam boiler only needed to be filled once a month, if that.

Jim Schulman recommends regular boiler flushes with distilled / 0 TDS water on HX machines to reduce or eliminate descaling - post #5 ZeroWater: New Water Treatment Option for Pourover Espresso Machines

just wanna make sure there is SOME mineral content, so the autofill sensor can sense the water.

Adding a spot of tap water will do it, and the random autofill pulling from the reservoir will keep adding a little bit overtime.

That would be the only concern Id have. And its easily taken care of.

This keeps coming up, usually concerning RO water, with more or less the same comment about the sensor. I've used for extended periods RO water in all my espresso machines including my Magister Stella (HX) with no overfilling problem (In fact, the one time I did have a mysterious filling/pressure problem the machine had tap water in it.) The TDS of my RO water varies from 4 ppm to 12 ppm. Admittedly, distilled water (~zero TDS) is slightly more pure than RO water. As a retired EET, I know the theory is sound; low TDS water should cause problems. On the other hand, I've never heard of anyone personally experiencing this problem. I'd like to see posts from those who have actually experienced overfill sensor failure due to using distilled or RO water.

Likewise, I've heard that RO and distilled water due to their purity, will leach metal out of the boiler. I don't doubt that a few ions are exchanged here and there, but wonder if it is significant. I put a penny in a glass of RO water and let it sit for months. It discoloured a bit, but there was no evidence that any significant amount of metal was disappearing. This reason not to use RO/distilled water would be harder to pin down, but I think it would be good to hear from anyone who actually experienced a problem with their machine clearly attributable to RO/distilled water.

Finally, there is the taste argument, which keeps coming up. Since HX machines (and nearly all home machines) use the same water for steaming and brewing, whatever water is put in goes into the coffee. Lately, I've been adding in a small amount of tap water (85 to 120 ppm TDS), mostly to see if the coffee tastes better (result: my tired old taste buds can't detect it if there is a difference). Again, I don't doubt that there is a difference, but wonder about the significance. Has anyone actually tasted it in actual use?

One correction - HX machines don't need to use the same water for steaming and brewing. Steam will come from the steam boiler, which is prefilled (with distilled water in my case), And brew water will come fresh from the reservoir/heat exchanger with whatever water i want to use. This is the approach I am taking.

Today I emptied my boiler as best I could and filled with distilled water. Had no issue with the fill sensor, so I suspect there was enough water still in the boiler to add a bit of minerals back into the mix.

I'm not too worried about leaching as the water won't remain perfectly pure for very long as I steam, etc through daily use.