The one thing that kills machines faster than anything else is bad water (lime scale). I realise some machines have internal water filters, but in reality they are about as useful as snowshoes in the desert.

They don’t soften for very long and in the tank for more than a few weeks they tend to go mouldy inside (so don’t bother trying to recharge them)! You are far better off using boiler safe water if you live in a hard water area.  This can be certain bottled waters (NOT mineral waters), Volvic and Tesco Ashbeck are names that spring to mind. It’s important to get the calculation correct for estimating whether the mineral water is soft or not. It is only 2 minerals that cause hardness.

  • MgCO3 (Magnesium Carbonate)
  • CaCO3 (Calcium Carbonate)

Soft water is usually below 60 mg/L (milligrams per litre) of the combined total of these compounds. Moderately hard is 60-120 and hard is 120-180.

You have to multiply the calcium number by 2.5 and the magnesium number by 4 to get the real amount (it’s just chemistry).

This leaves you with a few solutions

  • Bottled Water
  • Renewable cartridge systems
  • Reverse Osmosis

Jug filters and inline cartridges I have not found to be particularily effective

Bottled Water

An example of 2 bottled waters shown below the first (Ashbeck) looks pretty good for the machine with a total hardness of 35 mg per litre, so it’s pretty soft. The dry residue is 80mg per litre, this is also not too bad. Dry residue is that which is left if the water is all boiled away. It shouldn’t cause problems unless very high, but best aim for the lowest dry residue you can.

The main issues here are plastic waste, transportation, storage and ultimately cost

This next bottled water would be totally unsuitable. It looks good at first glance, but it’s hardness is 152 (fairly hard) certainly much too high for a coffee machine. The dry residue of 219 is also way to high for comfort.

Renewable cartridge systems

These usually have a fitting plumbed into the water supply, a screw in cartridge and a tap fitted to the sink. The cartridge is typically located under the sink. There are different types and you have to choose carefully to get the right type for a coffee machine. An example of one manufacturer is

The main issue is one of cost and inconvenience, especially if you are in rented accommodation where fitting such a device may not be allowed..

Reverse osmosis

For me this has worked out to be the most convenient solution and for the way I use it ultimately the most cost effective. It’s also great for flats and rented accommodation.

So whatever you do, be very careful to get it right or seek advice about the many cartridge systems available to give boiler safe water. I use reverse osmosis with bicarbonate re-mineralisation if necessary.