If you have an espresso machine, you will have limescale formation in your boiler. And you will have to descale it from time to time. And more often if your water is hard.
The main risk of not PROPERLY AND REGULARLY descaling is clogging your machine with small crystals that may travel through the system and reach a flow restrictor. This may permanently damage some components, affect the flavor of your coffee and also increase the energy consumption.
And when I say properly and regularly descaling, it’s to prevent things like this, that I found in a Gaggia Classic 2006 which, according to the previous owner, was regularly descaled:
In terms of health, I don’t know how bad it is since it’s just calcium carbonate that is not going to your cup? Maybe a biologist or a doctor can contribute here… I’ll ask a few people and update the post later, but I’m not courageous enough to drink a coffee from this boiler.
Index:
2 – How do I know if my water is hard or soft?
3 – What are the acceptable levels?
4 – What if I use water with zero TDS?
6 – Bill of materials for descaling
7 – Step by step instructions for the full descaling process
– Testing the electrical connections
– Testing for leakages and closing the machine
Disclaimer: this is the first version of a convoluted subject and cleaning process and I’m not a technician in espresso machine maintenances. My intention was only to raise the topic which seems to be neglected and share my best knowledge to help the community. Hence, do at your risk and if you feel prepared for these procedures which involves shock and burning hazards, among others. And if you find any flaw or points for improvements, please send a message to espressohackers@espressohackers.com.
So, what can I do?
First, to prevent limescale formation, I would avoid using hard water.
Second, you can descale your machine every 2-3 months with citric acid (40g/l of water) or the specific products/intervals recommended by the manufacturer.
If you bought second hand, or used tap water, and didn’t descale regularly in the last couple of years or didn’t descale at all in one year, I’d consider sending to the technical assistance or if you are comfortable in doing yourself, opening the boiler for the “hard” cleaning that I’ll describe below.
There are other parameters that you can monitor such as the water flow in your group. James Hoffmann recommends measuring the amount of water dispensed in 30s every 2 months (https://youtu.be/Bl7kuC1IQ-g?si=WZi5AxvUJhb3AXMo&t=977). When it starts to decline, it is potentially scale build up.
Another recommendation, from Whole Latte Love, was monitoring the chamber of the mushroom valve in a E61 group. If there’s some limescale there, you will probably have in other parts.
PS: in the video that I linked above, James talks about a frequent descaling with 2-5%. If you didn’t descale for a couple of years and you use hard water, the weak solution could not dissolve everything and some small particles could clog your machine. In this last case, an approach would be using a much higher concentration, 20% and leave it a lot longer to dissolve as much as possible.
Personally, I don’t feel comfortable in doing this, I’m afraid of still having some small bits of calcium carbonate clogging somewhere or corroding some parts. I prefer opening the boiler, descaling it, and visually inspecting. And I would also descale other parts such as pipes, group and solenoid valve (not the electrical part of course, only the tubes).
How do I know if my water is hard or soft?
You can get the data from your city administration if you use tap water, or from the labels if you use bottled water, and you may need an online calculator if they don’t provide the hardness levels. However, I can anticipate that it’s complex if you are not a chemistry related professional or student.
I’d just buy a cheap TDS meter on Aliexpress (https://s.click.aliexpress.com/e/_DEaNVrF) for around USD 5 and measure my water. This method is not super precise, but it’s easy and a smart approximation to give you some references.
In my case, I knew beforehand that the water in the Netherlands is much harder than ideal and bought a Zerowater kit including the TDS meter (https://amzn.to/415sVJl).
You can mix the water from Zerowater filter with tap water or remineralize it.
Other options to Zerowater are the expensive reverse osmosis systems, or buying distilled or deionized water.
Brita water filters (https://amzn.to/3Zywl5W) don’t remove as much minerals as Zerowater. In my tests with the TDS meter, Brita removed 25% and Zerowater 100%. However, Zerowater will be more expensive, I pay circa 16 euros per filter that can filter about 80 l (gross estimation) in a city with TDS at 240-250.
Now, you are wondering what are the acceptable levels?
According to La Marzocco “the ideal water for espresso extraction has a TDS of 90-150 ppm, with no extraneous odors or flavors that would interfere with taste, but still has enough TDS that the machine will be able to recognize it” (https://www.lamarzocco.com/tw/en/water-for-home-espresso-machines/#:~:text=Ideal%20water%20for%20espresso%20extraction,be%20able%20to%20recognize%20it).
The Specialty Coffee Association of America recommends a TDS between 35 and 85 PPM.
And what if you use water with zero TDS, would it prevent limescale formation forever?
That’s a tricky one. In theory, I believe that yes, it would prevent limescale formation since there’s zero calcium in the water. However, you need some minerals to extract the compounds in your coffee, but not much because it would mute the flavours as well.
Another risk is corrosion if your water is in the low extreme. This is a controversial topic, but I’ll leave the link with some information about water hardness: https://www.baristahustle.com/water-hardness/
If you want to go deeper into the science of water for coffee, how minerals like calcium, potassium and magnesium affect the taste of your coffee, the reference is Christopher Hendon and Maxwell Colonna-Dashwood. You can read their book (sold out but revised version to be soon released, it wasn’t until in Nov/2024), check some publications and videos like this one that is very comprehensive: https://youtu.be/h7Y3p2hTiFs?si=vB5RmLkhcR8H6Sqy
Please notice that water is so complex that even Maxwell and Chris are revising some concepts from the first to the second edition of their book, such as remineralizing the water or not: “The mineral salt choices themselves and the amount used both impact the brew heavily. The problem with using one or two mineral salts to make a water composition is that the resulting composition is abnormal and lacks the diversity found in typical waters whether filtered or not. Even utilising a wider array of salts has its challenges to match “natures” water. In the new book we explore this challenge and recommend some thresholds, whilst also recognising that source waters with a level of filtration will often provide a cleaner and balanced cup that displays origin characteristics well” (https://www.reddit.com/r/pourover/comments/1bemk3z/water_for_coffee_2_book_due_later_in_the_year).
What am I doing?
In my case, I’m using water with a TDS between 90-110 ppm. I didn’t descale my ECM Classika PID in the last 12 months, which may have been a mistake, but I’ll soon open the boiler for a visual inspection and take a decision on the “easy” descaling (2-5% concentration, few minutes and rinsing without needing to open the boiler) or the full descaling.
The reason why I didn’t descale is because I was monitoring the chamber of the mushroom valve as well as the 3 way valve, and I wasn’t seeing any sign of limescale. Soon, we’ll know if this method works or if I should have descaled before. You can bookmark this post and come back in 1 or 2 months, I’ll update this post with my findings.
The full descaling process
If you need to open your boiler for a full descaling process, this is how I did in the Gaggia Classic with that scaring boiler in the beginning of this post:
The Bill of Materials
The complete list of components, consumables and tools needed can be found in this Bill of Materials. Along this post I’m using links mostly to USA for illustrative purposes and for you to check the specs, but I’ll update later with more links for Europe and Aliexpress whenever possible.
In this list, all the specifications were checked but the seller may change over time (and it doesn’t mean that I didn’t make any mistake in the selection).
The descaling process is applicable to any boiler, however, I used a Gaggia Classic 2006 as an example to build this tutorial and you may need to check the specifics for your machine, e.g. screws size, gaskets’ specs, and logic tests for the electrical installation.
1 – Citric Acid or descaling solution: citric acid is cheaper, I paid EUR 3.5 in a local grocery store for 150g in Nov 2024, online you can pay less than 10 dollars or 900g (https://amzn.to/416doc2). I diluted circa 40g/l of water at 70-80 degrees, checking every 5 minutes and replacing the cold solution for a hot one from time to time.
I have already used the Saeco descaling solution in the past. It works well but costs circa 16 dollars per bottle (https://amzn.to/495GUAy) or 3 bottles for 24 dollars (https://amzn.to/3AUazQN). Saeco doesn’t recommend using citric acid or vinegar to descale, James Hoffman uses citric acid (https://youtu.be/Bl7kuC1IQ-g?si=Ef2DQ5k8zHFgh95y&t=893), make your choice.
A question that I always receive is if is possible to use Cafiza (https://amzn.to/3ZlpCfJ) or similar. And the answer is NO. They are not descaling products, they are detergents for coffee machines, and like any other soap, will remove oils and not limescale. It will also be hard to rinse if you circulate Cafiza in your machine, probably several litres of water.
2 – Brass brushes:
Manual brass brushes (https://s.click.aliexpress.com/e/_DdTZ7uV) vs Dremel brushes (https://amzn.to/4i56aet): the Dremel brushes can be quite aggressive, especially at high RPM. I’d consider only as a last resource for the most critical cases. In most of the cases, you will be able to clean your boiler with just the descaling solution and the regular manual brass brushes.
3 – Sanding paper: coarse to start and finer to finish. It may be needed to level the surface between the boiler and the group. I used a 120 grit.
4 – Gaskets: I recommend replacing all the boiler gaskets if you are opening the boiler, and also the group gasket. You may also want to replace the hoses, upgrade the shower screen and diffusion plate. Below a few links:
- Repair kits: https://amzn.to/4i5S3p5 or https://amzn.to/3OrpmFS
- Boiler gasket only: https://coffee-sensor.com/product/gaggia-classic-boiler-to-grouphead-silicone-gasket-code-12001021/ (please notice that there are different dimensions depending your model).
- Group gasket with grease included: https://amzn.to/49ojzdT
- Silicone hoses: https://www.bluestarcoffee.eu/en/ULKA-Silicon-Water-Inlet-hose-tube/m-471.aspx
- Molykote 111 (https://amzn.to/3Z00YQo for a USD 22 for a 150g tube or USD 10 for two 6g pack https://amzn.to/415qLtd): it is recommended to lubricate the gaskets with Molykote 111 or another food safe product like Haynes Lubri Film Plus (https://amzn.to/4eRFwTz USD 7.50for 115 grams). Molykote is a bit more expensive, but you will need a few grams per year if so, and the feedback from people that service these machines is that Molykote is thicker and lasts longer.
5 – Screws for the boiler: I recommend having some stainless steel screws at hand and I recommend replacing if they are rusty or you may break the screws in a next time and it’s a bit of a headache to remove broken screws. For a Gaggia Classic you will need 4 M6x16, but check the specs for your machine: https://www.bluestarcoffee.eu/en/Gaggia-Group-Screw-M6-x-16/m-4685.aspx
6 – You may consider making the OPV (https://amzn.to/3CETue0), dimmer, pressure gauge and PID mods. For the last 3, go to the main page where you will find all the instructions and parts needed.
7 – Tools:
- Wrenches: I used a 17 mm and an adjustable wrench (https://s.click.aliexpress.com/e/_DBAFM8F) only.
- Allen keys: I used 4 and 5 mm.
- Locking plier: the only thing that allowed me to remove two screws that were stuck. You can buy the famous Irwin vise-grips (https://amzn.to/4fJbgM1) for USD 15 or a cheaper one for circa USD 8.50 (https://amzn.to/3CJ8yr7).
- Multibits toolkit (https://s.click.aliexpress.com/e/_DCihKAT): for me it’s quite annoying to stop what I’m doing and go to the hardware store to buy that only bit or allen key that I don’t have. Then, I bought one of these kits, but depending on what you already have, you might not need, or buy just a set of allen keys or precision screwdrivers of better quality for the same price.
8 – Others: Philips and flathead screwdrivers, pliers, permanent markers, zip ties
Step by step instructions for the full descaling process:
Preparation
1 – WITH YOUR MACHINE COLD, drain the water from your boiler by activating the pump to release all the remaining water inside. TURN YOUR MACHINE OFF IMEDIATELLY AFTER TO AVOID DAMMAGING THE HEATING ELEMENT.
2 – For your safety, unplug your espresso machine.
3 – Take pictures or make videos of the disassembling process or you may not remember the sequence to reassemble, or which nuts and bolts go where.
4 – Remove the drip tray, the water tank, and the pipe that goes to the drip tray.
5 – Remember that the hoses will leak and you don’t want any drop of water in any electrical part.
Opening and disassembling
6 – Remove the lid on the water tank.
7 – Remove the two screws and carefully remove the top panel because the ground wire will be connected underneath.
8 – Before disconnecting any wire, label all of them.
9 – Remove the thermofuse holder:
10 – Remove the connectors gently to avoid breaking the plastic insulation. Many will be a bit tight, I recommend using a plier.
11 – Now that you have more space, loosen the copper steam pipe nut and the steam thermostat on the top. I used a 17 mm wrench here due to the limited space.
12 – In my upcoming video, the sequence was not optimal since I was trying to understand how to disassemble, but my recommendation is to follow the sequence described here.
13 – Loosen the nut (I used an adjustable wrench) that holds the PTFE tube and disconnect it from the elbow.
14 – Remove the nut that holds the discharging pipe from the solenoid to the drip tray:
15 – Pull the two silicone hoses from their holes to the top, one is connected to the OPV and the other to the pump. The objective is to have the boiler free to move when you remove the screws that fix it to the frame.
16 – If you didn’t do yet, remove the wires from the brew thermostat, solenoid valve and the pump.
17 – Remove the two screws that fix the pump to the frame. A magnetic screw may be helpful, especially for reassembling later. If you don’t have one, just be careful to not lose the tiny screws.
18 – Remove the pump and all the wiring if still inside.
19 – Remove the 4 screws under the panel that holds the boiler.
20 – Remove the boiler from the frame.
21 – Remove the screws that hold the solenoid valve, and the solenoid valve.
22 – Remove the two crews that hold the OPV and the OPV.
23 – Remove the brew thermostat on the lateral.
24 – Remove the screw that holds the shower screen and the shower screen.
25 – Remove the two screws that hold the dispersion plate.
26 – Remove the dispersion plate (mine was stuck).
27 – Remove the 4 screws that fix the top of the boiler to the group. If the screws are stuck, you may need a locking plier:
28 – Open the boiler in the sink or container since there will still be some water in the boiler.
29 – Remove the boiler gasket and clean the boiler inside, if needed with a brass brush, to remove the excessive limescale.
30 – If you didn’t do yet, remove also the group gasket. If it’s stuck, attach a wooden screw and pull with a plier. In my case, I had to do it a few times because it was in a super bad condition. PS: the screw should not trespass the gasket, just firmly hold it.
31 – Clean the group with a brass brush:
Descaling
The group you can soak in your descaling solution, but the top of the boiler not. THE TERMINALS OF THE HEATING ELEMENT CANNOT GET WET OR YOU MAY PERMANENTLY DAMAGE THE ISOLATION and in this case you may need to buy a new boiler.
32 – I diluted circa 40g/l of water at 70-80 degrees, checking every 5 minutes and replacing the cold solution for a hot one from time to time. Did the same for both the boiler and the group. However, the boiler was in a super bad condition and I had to replace the cold solution several times. The boiler I left upside down and put the solution only inside the boiler. From time to time, I brushed the inside to speed up the descaling process.
33 – There will be a point that visually, you may think that you didn’t remove 100%, there will be some white spots. If it’s not a crust, you should be fine. Excessively brushing is not recommended by technicians because the natural oxidation creates a layer that protects you from the excessive exposure to aluminium (polemic, but do your research) and it will be naturally re-created later. Then, it’s more for your visual satisfaction.
34 – At the base, if needed, you will need to level any big crust and let it plain enough to avoid leakages when you close the boiler again. In my case, the build up was only inside and I used only a small piece of sanding paper and gently removed the excess:
35 – The group was much easier to clean, but before descaling, I put it in hot water with Cafiza (https://amzn.to/3ZlpCfJ) to remove the oils and coffee residues first, then I brushed and put it in descaling solution for 5 min and brushed again:
36 – Before closing, you can wash and rinse the group with detergent and sponge. The boiler I recommend to rinse carefully since the heating element terminals cannot get wet.
37 – Lubricate the boiler gasket with Molykote 111 or similar, install and close the boiler.
38 – Before moving to the next steps, I recommend a simple continuity test in your heating elements to check if the isolation were preserved: with a multimeter in the continuity test or resistance measurement mode, connect one probe to one of the terminals and the other to the body of your boiler. If it beeps or the resistance is zero, you may have damaged the isolation and might need to replace the top of your boiler.
Re-assembling
39 – Before re-assembling, you want may to clean the frame.
40 – The first component that I recommend to fix is the pump because it will be more difficult to fix the screws later due to the limited space. Reconnect the wires as well.
41 – Re-install the solenoid valve, OPV, diffusion plate and shower screen in the boiler (undo steps 22 to 26).
42 – You don’t need to install the group gasket yet, but if so, apply a thin layer of Molykote 111. If doesn’t need to perfectly fit, you will finish the installation with your portafilter after reassembling the machine.
43 – If you are replacing the brew thermostat by a thermocouple to install a PID or the Gaggiuino mod, install your thermocouple in the lateral position (where the brew thermostat was). Otherwise, reinstall the thermostats in their original position.
44 – Position the boiler inside the machine.
45 – Insert the steam wand through its hole and fix the nut to the boiler.
46 – Put the black lid back:
47 – Insert the white silicone hoses in their respective holes.
48 – Fix the boiler to the frame.
49 – Reconnect the wires to the solenoid valve and the power internal plug.
50 – Fix the solenoid hose (black) to the frame (undo step 14).
51 – Put the thermofuse in the original position and screw with the original fixing (undo step 9).
52 – Reconnect the wires to the thermostats and heating element.
53 – Reconnect the wires to the switch.
54 – Reconnect the ground wires, remembering that one is attached to the top panel.
IMPORTANT: before turning on, double test the electrical connections
55 – I’d also recommend a few tests in the logic of your connections:
- With your Gaggia Classic off, you would expect energy flowing from one of the wires (labelled as 2 in my video) to the thermofuse, to one of the heating element connections (labelled as 13 in my video), to the pump (labelled as P2 in my video) and to the solenoid valve (labelled as S2 in my video). Disconnect 13 in your heating element. Connect one of the probes of your multimeter to 2 and the other to the points mentioned above, using the continuity or resistance test mode.
- Press the power button. The other phase of your outlet (labelled as 1 in my video) should flow to 4 in your switch. Connect one of the probes of your multimeter to 1 and the other to 4 and to the points below, using the continuity or resistance test mode.
- If you kept the brew thermostat, from 4, it should go to T2 in the brew thermostat, also on T1 because the thermostat will be below brewing temperature. If you installed the thermocouple and removed the brew thermostat, you need to put a jumper connecting the terminals that were in the thermostat to be able to make these tests (remember to remove after the tests).
- From T1 it should go to 17 and 9, and since the steam thermostat will be bellow steaming temperature, you should also see the energy flowing to 18, 15 and 12.
- Press the extraction button, and now the energy should flow from 1 also to 10, P1 and S1.
- Reconnect the wire 13 to the heating element.
56 – Connect the steam knob on the lateral.
57 – Lubricate the new group gasket with Molykote 111 and install in the group. If you cannot fit inside with your fingers, press with a round surface to avoid damaging the gasket. To finish, lock your portafilter in the group (without the basket), and it will accommodate the new gasket.
58 – Put the water reservoir back with water inside and connect the discharging pipe.
59 – Refill the BOILER with water. I refill the boiler by opening the steam valve and actioning the hot water button immediately after turning the machine on so that the pump can refill the boiler before the heating element gets too hot.
Testing for leakages and closing the machine
60 – First, I would extract some water from the group and from the steam wand without any pressure on the system.
61 – Check if you can see any leakage, any small drops of water in the frame, connections, around the end of the hoses fixed to connectors and around the boiler that you just closed.
62 – Then, remember to close the steam valve and use a blind filter in the portafilter to build some pressure in the system. Just lock the portafilter and turn your pump on for 10 seconds. Observe if there is any leakage.
64 – If all good or already resolved any leakage, connect the ground wire to the top panel, fix it with the two screws and put the lids back.