If the white residue tastes of lemon, you may have gotten something weird, like citric acid plus xanthan gum. But I doubt it. If you live in NYC, there's a good change you have soft water. This means descaling anything is a waste of time, and the white stuff is anodic corrosion* from the infamous Gaggia brass/aluminum sandwich boiler. (*In the presence of soft water, which is slightly acidic, a join between two metals acts like a battery, with the anode, in this case the aluminum, supplying the metal ions. This means the aluminum gets eaten away. This is called anodic corrosion)

These boilers work and descale great in the hard water common in Italy, but they can fall apart in 6 months in very soft water. If you live in the part of Manhattan or Brooklyn that gets the Finger Lakes water, your machine is probably close to toast already. Alan Frew from Oz, where the water is similarly soft, once had lots of pictures up of corroded Gaggias. I'm not sure if they are still around.

Jim, 2 months with soft water will destroy the boiler? That seems odd. I would not think that one would need any type of descale after that short of time.

Apparently, some Gaggia boilers can malfunction after 6 months of very soft water. In that scenario, you'd start seeing corrosion coming out of the boilers after descaling almost immediately.

Again, I don't know if this is the problem. But if the white powder tastes like nothing, it's corroded aluminum oxide.

When my Gaggia boiler started pitting due to 4+ years of 6.5 pH Brita filtered water, the aluminum oxide bits were gray/black in color and heavy enough to sink to the bottom. I'm guessing (and hoping) that if your residue is white and floats, it may be scale deposits.

I am updating my initial post and thanks to everyone so far--I used clear glass measuring cups to see better last night and today:

Here is a more accurate picture of what it happening:
1)When I flush water through the group, I get something that looks like a somewhat cloudy suspension, like there is very tiny snow throughout the water. But as I waited and watched, these are actually not white particles but some kind of residue that eventually dissipates -- the surface residue actually moves a lot and you see tiny "bubbles" moving away from the center and towards the outer sides of the measuirng cup. AFter a few minutes, the water is clear but small bubbles remain on the outer walls of the cup. This is something like the phenomenon when you have cloudy, whitish-looking hot water come out of your sink faucet and if you let it sit a while the water becomes clear.

2)Last night the water I flushed through the steam wand looked clear--although 1-2 sand-sized gray particles (maybe aluminum?) were floating in the center of the cup during one test. Only once.

3)This morning the group had the same stuff coming out in the same manner AND a small amount of the same residue came out of steam wand.

Now I am seriously concerned that I am consuming aluminum or aluminum oxide. I don't know how to tell. It is tasteless and NOT citric in flavor. I don't know what calcium residue would look like (if it is not in the form of chunks or actual particles). Also, I flushed 2 tanks of water through and this did not remove the stuff. I don't want to get poisoned.

I live in Queens. As far as water, I don't know how it is. I thought the whole purpose of descaling was to take care of what is left by the water. I do use Brita filtered water.

Anyway, any other ideas on what this residue is, how I can find out what it is, and how to get it out for good. Is it possible it will never stop coming out?

Thanks to everyone again. I really appreciate your help.

Might not be the machine at all. It would be interesting to see the results if you were to try bottled water. Also if your water has a high ph, adding a pinch of baking soda will not only tame the acid but add back in a bit of flavor that filtering removed.

The white cloud that quickly dissipates is gas escaping. not a problem.
After all this clears, any solid particles are a problem. The best way to check for them is to flush the boiler through the steam wand.

Let the machine get fully warmed up, boiler full. Then turn on the steam switch and wait 30 seconds or so. Now open the steam valve fully and turn on the pump (brew button. ) Collect 6-8 oz in a cup and examine for solid particles. Based on my experience I'm betting anything white colored is mineral scale deposits and anything gray/black is aluminum oxide pitting from the boiler.

Brita filtered water is generally acidic, this is a problem in Gaggia aluminum boilers. You can get a pH tester at a Pet store for fish if you want to check it.

Gime2much wrote:Might not be the machine at all. It would be interesting to see the results if you were to try bottled water. Also if your water has a high ph, adding a pinch of baking soda will not only tame the acid but add back in a bit of flavor that filtering removed.

But this never happened until immediately after the citric acid event.

Frost wrote:The white cloud that quickly dissipates is gas escaping. not a problem.
After all this clears, any solid particles are a problem. The best way to check for them is to flush the boiler through the steam wand.

Let the machine get fully warmed up, boiler full. Then turn on the steam switch and wait 30 seconds or so. Now open the steam valve fully and turn on the pump (brew button. ) Collect 6-8 oz in a cup and examine for solid particles. Based on my experience I'm betting anything white colored is mineral scale deposits and anything gray/black is aluminum oxide pitting from the boiler.

Brita filtered water is generally acidic, this is a problem in Gaggia aluminum boilers. You can get a pH tester at a Pet store for fish if you want to check it.

It takes about 5 mins to dissipate. What would cause gas to be in the water?
I have been running water (full reservoirs of it) through the wand and the group and sometimes the wand water is completely clear with no problem at all. Sometimes it has the residue but the residue is way worse through the group so I can't figure out why that would be different than water from steam wand either.

What is the appropriate pH range if I get the tester?

Thanks.

EspressoGirl wrote: ....... the residue is way worse through the group so I can't figure out why that would be different than water from steam wand either.

What is the appropriate pH range if I get the tester?

Worse out the grouphead sounds like coffee residue maybe? Have you removed the shower screen and diispersion block for a good cleaning lately? Do you backflush the machine? (edit: just read where you did 4 days ago, but I would open and clean behing the shower screen and dispersion block)

pH should be 7 or above.

I really don't know what would cause your water to have 'excess gas'