While the timing of the problem start could be a good clue, I find in any kind of trouble shooting eliminating all possible causes starting with the cheapest and easiest ones is the quickest way to a solution.

Frost wrote: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'

You mentioned the gas--that is what I was wondering about--what could that be?

I clean the shower screen in Joe Glo and did that last weekend. It was descaled too. I clean the dispersion block regularly too. It doesn't look like coffee -- just this filmy bubbly stuff. But there is really a lot from the grouphead. And sometimes some from the steam wand.

Do you know the upper limit of good pH (I know that can go too high too...)?
Thanks.

EspressoGirl wrote:You mentioned the gas--that is what I was wondering about--what could that be?

I clean the shower screen in Joe Glo and did that last weekend. It was descaled too. I clean the dispersion block regularly too. It doesn't look like coffee -- just this filmy bubbly stuff. But there is really a lot from the grouphead. And sometimes some from the steam wand.

How much detergent do you use for your backflush? I'm wondering if the filmy bubbly stuff might be soap residue in the group and water path from using too much detergent. If that's a possibility, backflush with plain water until it goes away (2-3 seconds max per backflush.) You might want to drain and flush the boilers with bottled spring water, too. Crystal Geyser or Poland Springs should be safe scale-wise but will have some mineral content as well.

I'm not a water or minerals expert, but perhaps aluminum oxide debris swirling around in the boilers is somehow causing small air bubbles to get trapped in the water. Then it comes out of solution when it exits the group. The bubbles could be filmy because they're picking up a small amount of normal residual coffee oils.

Just wanted to add a bit of thoughts;

The bubbly water might be due to the pumps used on these machines. I do a fair bit of weird installations, and one of these are pressure sensitive membrane pumps for boats and RV's, or houses were fresh water is stored in tanks. These pumps seem to somehow (I haven't bothered looking up the physics behind it) agitate the water to the point were it exits the faucets "bubbly", almost like a soda. These bubbles disappear fast in a similar fashion as the OP described. Is it possible that the cheap vibe pumps (which I take are a version of a membrane pump) used in these machines could agitate the water in a similar fashion?

Did you ever try to descale it again? With proper citric acid? You can get the really chemically pure stuff from a pharmacy or brewing supply store, that way you know it's nothing but citric salt in it.

another_jim wrote: 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)

I have not yet read all the replies but the above is absolutely true. Water from upstate lakes used in NYC and Westchester County is about 50 ppm TDS will not require descaling after a year yet alone two months.