Filtration for espresso machines with stainless steel boilers

When selecting a water filter for your coffee machine, three key areas of filter performance should be taken into consideration:

  1. Sediment reduction– removal of algal spores as well as small particles of dirt, sand and rust will protect the flow path of of your machine. It will also prevent the boiler from accumulating sediment which can form a “sludge” which acts as a catalyst for scale development.
  2. Chemical reduction– reduction of chemicals such as chlorine which will negatively affect the taste of espresso
  3. Total hardness (TH) reduction: This refers to the presence of Magnesium and Calcium salts in the water. Some of these salts can precipitate to form scale. This scale coats boiler surfaces elements, valves, solenoids, gicleurs and water flow paths. Scale buildup can adversely affect water temperature, pressure, steam performance, water flow rate and taste. Whilst scale can be removed by chemically “descaling” the machine, minimising the accumulation of scale with the use of appropriate filtration will dramatically slow the rate of accumulation. Descaling requires the use of acid and this acid will ultimately degrade the thin copper tubing used to link machine components. We do not recommend routine descaling, rather the use of appropriate filtration. 

Whilst most filters adequately achieve the reduction of sediments and chemicals quite successfully, scale reduction is a little more complex. Please note that a drinking water filter as recommended by a plumber of retail store is unlikely to be a softening filter: i.e it will not remove scale. The use of a softening medium in a water filter can achieve a reduction of scale causing compounds of up to 90%.

Water softening is frequently achieved with the use of an ion exchange resin. This process involves the exchange of scale causing Calcium and Magnesium for Sodium. Whilst some Calcium and Sodium compounds are insoluble and deposit as scale, Sodium compounds are generally soluble and pass harmlessly through the espresso machine. Water softening reduces the total hardness of the water to an acceptable level without significant change to the pH of the water.

Total dissolved solids (TDS)

Total dissolved solids is a measure of all dissolved minerals in the water. A reading of over 300 parts per million (ppm) would suggest that a more complex filtration solution may be required to protect your machine. In general, Reverse Osmosis (RO) systems are not recommended for use with home espresso machines unless a remineralising medium is in place as well. RO is energy hungry and and wastes large quantities of water as well. Espresso machines rely on water conductivity to sense the presence of water. RO systems produce water without ionic content. The result is that the machine may not fill or may overfill with water.

How do I find out my TH and TDS?

Talk Coffee has testing equipment to test for TH, TDS and chlorine. Bring a water sample with you in a drinking water bottle and we can run a quick test for you. Comprehensive tests can be obtained for a small charge at places such as swimming pool chemical stores and aquariums. Your local water authority will also be able to provide general information. Note that water quality varies seasonally, so do ask for upper and lower levels. Our experience is that water quality can vary dramatically from house to house within one street, so the best results will be obtained with a test of your water.

My water is not that hard. Do I still need a filter which softens the water?

The heating and cooling of water in espresso machines is is the primary reason for scale formation. Home use machines are often switched on and off more than machines in commercial environments. This makes scale formation more likely- even in areas where the water is considered to be soft. The smaller boilers of home machines can further accentuate this. Please note that the level of scale reduction can and does vary according to the type of resin used in the filter and the local hardness of the water source. We recommend that regular use of the hot water available from your machine- to heat a cup of for a long black or cup of tea is a good thing. It helps flush scale causing minerals from your machine.

Will a Brita jug from the supermarket do?

Whilst these claim to soften water, the reality is that they’re good for a few litres at best. These jugs are really just for drinking water.

My machine has a resin softener attached to the inlet hose.

Whilst better than a Brita jug, in our experience, these do little more. The resin can be “refreshed” by removing the filter and soaking it in a tall glass of cold salt water every couple of weeks. We would only recommend these in areas of TDS <40ppm. If installed on your machine, they will not influence additional filtration and can be left in place.

Can I help prevent scale?

Yes! If you have a heat exchanger (HX) or dual boiler machine, use the hot water from your machine each day. Heat a cup or make a cup of tea. Many users never use the hot water- effectively removing water vapour as steam and then concentrating minerals in the boiler. This can lead to significant scale deposition even in areas where the local water is quite soft. Using water from your boiler will help dilute scale causing compounds.

What do I need?

In areas where TDS is under 250ppm, we recommend the Brita C150 finest which MUST be installed vertically. This filter employs a buffering system to maintain water pH whilst softening water. Conventional filters can lead to acidification of water where TDH is higher. The key issue is that the high requirement for softening resins can lead to the presence of chloramines  as well as acidification of water and this is frequently fatal for stainless steel boilers.  This filter overcomes this problem. We are now recommending that this filter be used wherever possible and always with machines which employ stainless steel boilers.

In areas of high TDS (over 300ppm), our information is that in cases of high TDS or high  Chloride (>100ppm) and/or Chloramine concentration, mains water will require reverse osmosis and remineralisation. We recommend that you have your water professionally tested to determine if this applies to your situation.

The options for these areas are:

  1. Filtered rainwater (if you have a tank). Ensure that the water is sanitary and use basic sediment and carbon filtration- as offered by most filters
  2. Use bottled water with low hardness (Ca and Mg), TDS and Chloride ion concentrations. The company selling the water should have specifications/readings they can give you
  3. Reverse osmosis with remineralisation. Aquacafe S900 P5 Reverse Osmosis system with remineralisation
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