This is correct with one caveat. With commercial descaler, you will not neutralize the acid to a safe level with the scale in the machine, so one needs to watch the time. The 1.5 to 2 tablespoon citric per liter solution will be neutralized by heavy scale, and isn't all that aggressive to begin with, so it can be left in for a while. I go overnight on cold machines and 2 to 4 hours on a hot one (depending on how lazy I've been in scheduling).cannonfodder wrote:It really depends on the solution you use. I use a commercial descale solution that is very strong. I descale a commercial boiler that was many years old in 2 hours and it was clean as a whistle. That same solution will dissolve the edges off of copper bolts and hex heads if you leave it in solution to long, it is very strong stuff.
So the soak time needed will depend on the solution used to descale the machine, the severity of the scale and the temperature of the water. The hotter the water, the more aggressive it works.
The usual caveat -- this citric solution is roughly 50% to 75% the strength of lemon juice, and it'll pick up light scale. If you have a heavily scaled part, or a valve, orifice, or piping junction, that has scaled severely (even if it's not that much calcium), it won't do the job in a reasonable amount of time. You'll need to take a part like that out, sit it in a commercial or higher concentration of citric, and remove the chunks as they come loose. I've had emails on parts that would scale severely in a few months even with fairly soft water. A simple citric flush didn't do anything for them. These generally are found on new models, since such parts' designs are revised when they show up.
I have a force fill switch on my Tea for descaling, works great. I tried a 3 position switch with a grounded third position that disabled the autofill entirely, so it wouldn't mess up my shots. But after I forgot to put it back after a hectic session, I gave up on that idea.
Speaking of autofills -- since they carry current, they can attract scale (and an odd pasty sort of grunge) even in soft water. It's worth cleaning off the wand once a year, when doing a descale. Make sure to use a marker before removing it, so you know how deep to push it back.