Descaling
Started descaling the plumbing and boiler with some citric acid. The boiler had about 8mm of scale in the bottom…so much so that the drain plug was missing and it was still holding water. Based on calculation, it holds 12 liters of water. When it started leaking, I realized the only thing holding water in the boiler was the scale itself. Add that to the list of replacement parts…
Most of the copper tubing being descaled 
The 12 liter boiler being descaled, one half at a time
