I'll be attempting this soon, and have tried to make Chris's useful article easier to read.This post in response to http://coffeesnobs.com.au/YaBB.pl?num=1274612190
The topic comes up pretty often, so it has been made a sticky item.
Its not that tough and Id be thrilled if I saw more machines in good condition rather than being full of barnacles. Its not a job I enjoy. :
I use Bombora activated descaler and one batch will normally do 2 descales for mild to moderate scale. Its cheap and effective. For bad scale, I use the lot (100g).
There is danger here as you will be working with a powered on machine and the job must be undertaken with extreme care. If you are not competent and dont hold the appropriate qualifications, leave it for a technician. 240V and water are not happy partners.
To descale a HX machine:
- First, with the machine switched off and cold, remove the mushroom (large hex nut on top of group) and examine for scale. If you dont see significant scale, you can stop here.
- Disassemble the machine sufficiently to allow access to the boiler water level probe
- Switch the machine on and allow it to come to working pressure. Start with a boiler as close to empty as possible. This is achieved by allowing the machine to come to pressure, switching it off and then opening the hot water wand. Boiler pressure will do the rest.
- Mix the descaler (not store purchased citric acid) according to the instructions
- Switch the machine on and allow the boiler to fill with descaler and the machine to come to pressure
- Key bit. Open the steam wand, remove the wire from the boiler probe and allow the machine to drink until descaler appears out of the wand and then replace the boiler probe wire. I often flick the power off then as you want to keep things dry in there. Close the wand off.
- NB. With a full boiler, some descaler may leave through the anti vac valve. If required, I open the steam wand for a bit and use towels if required to keep things dry.
- Allow 15 min and then run a little descaler through group and both wands..
- Repeat every 15 min until all the descaler is gone...Every time the machine drinks again, do the boiler probe bit again...
- One the descaler is all used, repeat with water from the beginning to rinse the boiler- but the 15 min bit can be omitted. I do this at least 3 times for 3 complete boiler flushes.
Its a fiddly job, and if youre not confident around electrikery, its not for you. AM has the emote to show you why....
We charge $150 + parts- because to do the job properly, it takes 2-3 hours.....Other service agents will do it as part of a service and charge pretty much nothing. They just throw some descaler in the tank and rinse the boiler. That approach wont work for HX machines as the boiler is only ever 1/2 full. It is however fine for single boiler machines- like a Silvia for example. Multi boiler machines are treated like a HX machine, but then the brew boiler may need to be flushed more or completely drained to clear it of descaler.
All of this will probably still be insufficient for really severe scale- the only option being complete disassembly.
Hope that helps.
I will try to add some photos of the process.