edwa wrote:Interestingly, neither of them recommend descaling their Hx machines.
They're advocating water softening such that no scale is produced, not that you should do nothing and allow scale to build unabated. That's sound advice. The water in my town is soft already, so I monitor the "e61 mushroom" to determine if scale is building up:

My machine's has never reached the point seen below:
See Sputtering e61 & HX scale build-up - Cured! for more detailsedwa wrote:One reason given is that the descaling solutions will eventually pit the insides of the boiler.
Jim's
Water FAQ advocates "preventative descaling":
another_jim wrote:Descaling Solution - Generally, a flush through descaler uses about .5 to .75 fluid ounces (1 to 1.5 tablespoons, or 8 to 12 grams) of citric or tartaric (grape) acid powder dissolved in 1 liter of water. This is a 2.25% to 3.5% solution, equivalent to 33% to 50% dilute lemon juice. Cleancaf and other coffee manufacturers' descalers use this formula. Theoretically, these amounts will dissolve about 12 to 18 grams of scale per liter, but that would require leaving the solution in for several days; in practice, it is used for an hour or two to dissolve up to 5 grams of scale.
The formula is mild enough to be harmless to espresso machine components, but it will come out of brass or copper machines with a slight greenish tinge. This comes from milligram levels of dissolved copper and is no cause for alarm.
I would be surprised if a strength equivalent to 33% to 50% dilute lemon juice could pit the inside of the boiler, but I don't have Chris or Jim P's repair experience to refute their assertion.