Image displaying the orange contents of the tube test glass

Coffee machine water filters and water hardness test kit

Why use a coffee machine water filter?

First of all, the most important reason, preventative maintenance. The majority of coffee machine breakdowns are directly related to scale. A coffee machine water filter will protect equipment from this risk, when used correctly. For best results combine this with a water hardness test kit.

Secondly, to prevent the passing of unwanted particles, into machines. The most commonly found particles in water are rust and silica.

Heavy metals such as copper and lead as well as organic pollutants and pesticides must be filtered. Chlorine in water can make a good quality coffee taste awful.

Put simply all of the above will degrade the taste and the aroma of coffee if left unfiltered. Moreover the appearance of coffee and tea is completely different when made with filtered water, it will be darker and if left a scum cloud will appear on the top.

Filtered water accelerates the extraction of flavour in coffee. This is subjective, however it is obvious to everyone that filtered water always makes a better coffee. This is even more so when the filtration enables the quality of water to fall within a certain crosshair of variables.

Image displaying a coffee machine water filter head.

Coffee machine water filter head.

How calcium enters rain water

Rain collects carbon dioxide whilst falling through the air. Carbon dioxide then sieves through the ground collecting solid lime scale (CAC03). The scale is dissolved by the Carbon Dioxide and retained within the rain water mixture.

The result is CA2+ (Calcium) and 2HCO3 (hydrogen carbonate), a deadly combination so far as coffee machines are concerned.

When disaster strikes

The nasties contained within tap water mostly fall under the description of TDS, aka temporary dissolvable solids. TDS is also referred to as carbonate hardness. The levels of TDS can be detected using the water hardness test kit.

Temporary dissolvable solids dissolve when water temperature reaches 60 degrees and above. When this happens all hell breaks loose and the destruction of expensive machinery begins.

The breakup or separation of hydrogen carbonate into carbonate and carbon dioxide occurs at a temperature of 60 degrees and above. The carbon dioxide is burnt off leaving calcium and carbonate to team up creating a near insoluble danger. It’s lime scale precipitation time.

Image displaying a water hardness test kit with a purple result.

Water hardness test kit after adding a few drops of testing liquid, the water turns purple.

How a coffee machine water filter works

All good coffee machine water filters work predominantly using a process named Ion Exchange.  Calcium is a component of lime, hence the phrase lime scale. Calcium or CA2+ is drawn to the Ion exchanger whereby Hydrogen is released.

In simple terms the Calcium is exchanged with the Hydrogen and the calcium is cancelled out. In a Brita filter the Ion exchange happens with beads. The beads have a limited life span. When filtering capacity is quoted as an input of litres or one year whichever is sooner, this is why.

Once the beads have been compromised they will only last for a maximum of one year. This is regardless of how much or little water is put through. Filters are a food safe product, the 12 month maximum is therefore very important.

The hydrogen Ion exchange system is only applicable to Brita filters of the type Purity C. At Happy Donkey this is the system used the most.

The Purity C Brita filters use either a standard 30% bypass head, or an adjustable 0 – 70% head. The purity C filter cartridge contains both non Ion exchange resin and ion exchange resin. The level at which the bypass is set to, determines the percentage of water going through the non Ion exchange resin beads only.

In simple terms set the head to 70% to allow only 30% of the water through the Ion exchange part of the filter. The 70% remaining water will only be filtered by the non Ion exchange beads (activated carbon). The two meet at the other end and flow as one. So beautiful.

Image displaying brita coffee machine water filter heads from the front view.

The two coffee machine water filter heads, left is the 0-70% adjustable model and on the right is the fixed 30% bypass version.

Ion exchange resin

Filters and works like a magnet attacking scale and heavy metals examples being copper, lead and Aluminium. Ion exchange helps to promote great tasting coffee with a good aroma. Protects coffee making equipment from lime scale and magnesium..

In the Purity C filter this is the 2nd stage of filtration, the first being the filtering of large particles via a particle filtration fleece.

Activated carbon in a coffee machine water filter.

A black particle bead that filters like a sponge would. Made from coconut shells. Excellent at absorbing chlorine, pesticides, odour and organic particles. Reduces carbonate hardness levels. Carbon is a proven bacteria killer. This is the 3rd stage of filtration in the Purity C filter.

The final stage of filtration involves holding back the finest particles found in tap water.

Image displaying Ion exchange and activated carbon filter beads

Ion exchange and activated carbon beads.

The water life cycle.

Water is not born bad. Rain water is slightly acidic by nature. It is the journey of the water, once earth bound which dictates the held qualities and attributes.

Water settled and worked through a lake will have a completely different profile to that which has settled and worked through porous rock. Water is a product of the environment in which it travels through, much like people.

Supplied Water in the uk in modern times does not necessarily originate locally.

The knock on effect of this is the practice of pumping water up and down the country as required. There is no longer such a thing as a permanent hard or soft water area any more.

The focus therefore should not be on the area in which we are working but the water which we receive from the tap in that area.

Image displaying the water hardness test kit components.

The water hardness test kit comprises of a tube and tester liquid, easy to use for accurate results.

Testing water for Carbonate hardness using the water hardness test kit.

Testing for carbonate hardness is a great place to start when figuring out what filtration is required from a coffee machine water filter. Using a Brita adjustable bypass ratio head it is possible to get really accurate filtering of the water used to make the coffee with.

Shown below is the measuring guide using the Brita carbonate hardness testing kit.  Use the result of the kit and the chart below it to work out what filtration is required.

Instructions for using the Brita water testing kit.

  1. Run the cold  tap for 30 seconds
  2. Fill the tube with 5ml of cold tap water
  3. Counting  each drop carefully, add one drop of test liquid at a time
  4. When the liquid turns yellow stop. The amount of drops used to get to yellow is the carbonate hardness or KH score.

If uncertain of the colour add one more drop, if the yellow does not get stronger as a colour then use the previous count, ignoring the last drop. Most noteworthy is if warm or hot water is used in the test a false result will be given.

Image displying the water hardness test kit with yellow liquid, this test is complete.

The liquid has turned hard yellow, this indicates the water hardness test is complete.

Using the water hardness test kit result.

Presuming the result of the test was a score of 4 or above. The charts indicate various sizes of Brita Purity C cartridge. How much effective capacity of filtration they will give and level of bypass to use.

In the first chart a recommended bypass is shown in relation to the score. This makes the presumption a 0-70% variable bypass head is being used. This chart is for espresso, coffee and vending machines.

For example if the carbonate hardness test score is 8 then a 50% bypass setting on the adjustable head is suggested. Looking across the column we see a Purity C500 cartridge will effectively filtrate 10094 Litres of tap water.

A litre is 1000 ml, a double shot of espresso is 60ml. Therefore it is usual to expect around 16 double shots of espresso to every litre. We have 10,000 Litres, so we should get approximately 16,000 double shots from that filter on a 50% bypass setting. Or one years use whichever comes soonest.

The Brita Flow meter is worth a purchase, this will record exactly how much litreage has passed through the machine.

Most noteworthy is the ability to remember that coffee machine are not only used for espresso shots. All water run through the espresso coffee machine should be accounted for and added to the used volume figure.

To be safe take away 20% of the volume to start with then divide the remaining figure by 60. If all this does your head in, mail the result in to Happy Donkey and it will be done for you provided the water testing kit was purchased at Happy Donkey of course.

Espresso, Coffee and Vending machines Brita Purity C using 0-70% head, bypass showing litres based on Brita filter cartridge size.

Carbonate Hardness scoreRecommended by-pass settingPurity C50 capacity in LitresPurity C150 capacity in LitresPurity C300 capacity in LitresPurity C500 capacity in LitresPurity C110 capacity in Litres

More charts

Next is the 30% bypass chart, this also applies to espresso coffee machines and presumes the fixed 30% bypass head will be used. The same prinicple of measurement should be used as discussed above. Again use in conjunction with the water hardness test kit.

Brita Purity C using 30% bypass showing litres based on Brita filter cartridge size.

Carbonate Hardness scoreRecommended by-pass settingPurity C50 Capacity in LitresPurity C150 Capacity in LitresPurity C300 Capacity in LitresPurity C500 Capacity in LitresPurity C1100 Capacity in Litres

Going hardcore with the filtration this chart uses figures relating to a 0% bypass.  This is not usually a good idea, but if the urge is there here is the data.

Brita Purity C using 0% bypass showing litres based on Brita filter cartridge size.

Carbonate Hardness ScoreRecommended by-pass settingPurity C50 Capacity in LitresPurity C150 Capacity in LitresPurity C300 Capacity in LitresPurity C500 Capacity in LitresPurity 1100 Capacity in Litres
4 - 60%100025084167708311979

Last but not least a chart for those using the Purity C on a combination or conventional oven. Note well this chart relates specifically to steam filter heads an cartridges which is different to a coffee machine water filter.

Combi and conventional oven filtration using Brita Purity C with 0-70% head, bypass showing litres based on Brita filter cartridge size.

Carbonate Hardness scoreRecommended by-pass settingPurity C50 capacity in LitresPurity C150 capacity in LitresPurity C300 capacity in LitresPurity C500 capacity in LitresPurity C110 capacity in Litres

Which coffee machine water filter?

Generalising is a dangerous thing to do with water filters for coffee machines. Most noteworthy is the requirement to test the water and use the charts above.

If time is of the essence and a filter needs to be ordered before testing can be done, then as a ballpark figure note the following:

1 group machine – Purity C300

2 group machine – Purity C500

3 group machine – Purity C1100

1 or 2 group machine in a very soft water area – Purity C Fresh

Please do not buy a filter and then not bother to test the water. This can lead to problems.

Image displaying a c150 coffee machine water filter

Brita Purity C150 filter cartridge top.

When water bites back

Water becomes active when stripped of all  mineral content. What this means is the water actively seeks to take on minerals and metals, strange but true.

Over time active water can eat holes in copper boilers and pipe destroying a coffee machines internals. This will be true of water which is over filtered or even run through a reverse osmosis system.

Selling a coffee made with reverse osmosis water is illegal in the UK. This is for health reasons. Water carries nutrition which helps the human body.

This highlights the importance of using a water hardness test kit before a coffee machine water filter is fitted.

Coffee machine Water fIlter for domestic espresso machines.

For machines enabling access to the water intake pipe in the tank, there is the domfilter. A domfilter contains the same Ion exchange and active carbon beads as the commercial machine filters.

Use of bottled spring water such as Highland Spring can reduce the amount of inpurities going into the machine. Spring water certainly does away with Chrlorine and pesticides too.  Most noteworthy is that spring water does contain calcium, so be aware.

Filter jugs can also work well, for best results use the water hardness test kit and combine all three of the above. The battle against scale is never over.

Image displaying domfilters for domestic espresso coffee machine filtration.

Domfilters are a great way to keep scale at bay ! Cheap and effective domfilters can save a lot of heartache in the future.

To buy any of the items mentioned in the article buy at Happy Donkey.

Keeping the water supply filtered is important and so is keeping coffee grinders clean why not give this a read: guide to cleaning coffee grinder blades

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