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De-Scale - Back
1. Your water kettle in your kitchen will give you a good indication as to when you need or how often you need to De-Scale your machine. “At least as often as you need to clean the mineral deposits from your water kettle (by number of uses), you will need to clean your machine.”
2. If you have never used citric acid powder, buy some extra. A ¼ teaspoon in 12 ounces of water will de-scale your water kettle as new, a little more will de-scale your Silvia or it can just be added to your kitchen spices.
3. Find a good 12 ounce paper or plastic cup that can be wedged in the water tank with its rolled edge supported by the sides of the tank.
4. Remove 2/3 water from the water tank and fit the cup into the tank suspended from the top.
5. Now we need to empty some water from the boiler. The best way is to not allow the boiler to recharge after steaming milk which can be simulated by steaming some cold tap water. To do this, put some water in your steaming pitcher, turn on the steam switch and allow the boiler to heat to steam temperature. Open the steam valve with the wand in the pitcher and steam the water as you would steam milk. Yes, you can just let the steam run to the open air for the same amount of time you would normally froth milk.
6. Stop the steam and turn off machine. The PID should be off during the following procedure (until step 11) so the PID will not heat up the boiler; this way you will have the full control over the boiler (if your PID does not provide the on/off option, lower the temperature setting on the PID to zero or lower).
7. Fill the cup with water and add 1 flat teaspoon of citric acid. Mix with a plastic spoon because the citric acid will eat the finish on some metals. The citric acid solution is kept separate from the water remaining in the main tank to reduce the possibility of the solution dripping on the machine and to make a later flush with clean water easier.
8. To fill the boiler with the citric acid solution from the paper cup: Put the intake tube and the overflow tube in the cup. Place a pyrex glass under the steam wand, open the steam valve to let out the air and run the pump by turning on the machine and then the water switch to fill the boiler with the citric acid solution. Close steam valve when all air is out (water solution will start coming out of the wand) and stop the pump.
9. Any acid solution that came out of the steam wand and is still clear can be put back in the paper cup. If the solution that came through is already a blue/green color, the acid solution has already started to work.
10. Force some of the acid solution through the OPV by closing the steam valve, turning on the water switch, counting to 5 and turning off the water switch. This will force some of the acid solution through the OPV into the over flow tube and back to the paper cup in the tank. Now the boiler will be full and the citric acid solution will be spread throughout the machine.
11. Turn “on” the steam to heat up the boiler to between 212 and 230 on the PID readout and turn off the steam switch. This will have the effect of boiling the acid solution which accelerates the descaling process.
12. Cycle the water pump for 4 ± seconds to circulate hot water with acid through the OPV. and also let some solution out from the steam wand, (less then 1oz).
13. Turn off the machine and let it rest for 30 minutes with the citric acid solution in its boiler, tubes, fittings and piping. Then, turn on the brew switch to flush about 4 ounces of liquid into a bowl or cup placed under the grouphead just to see the color of the water.
14. Repeat steps 6 to 12 if the used acid solution came out very blue/green color or steam valve is not turning smoothly, you can reuse any remaining clear solution. If you are de-scaling after you have backflushed the machine with detergent so that the grouphead is free of oils, you can put a blind basket in the portafilter and turn on the brew switch momentarily to allow some of the solution to soak the grouphead. It will make the brass cleaner.
15. Once the used citric acid solution is coming out near clear, flush the machine, boiler and all tubes with at least one 1/2 liter of fresh water--or until the water coming through does not taste like lemon juice (if you want to taste it). During the fresh water flush make sure you flush the OPV and the overflow tube, by closing the steam valve and make sure the brew switch is off with the water switch “ON” to force clean water through the OPV to the overflow tube. To avoid having to take out the tank and fill it and put the tubes back during this flushing process, you can pour the fresh water into the cup after disposing of the used citric acid solution in the sink (with fresh water running).