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Water hardness and the Miele dishwasher

Have you ever been a little confused about the issue of water hardness for Miele Dishwashers? Don’t worry, you’re not alone.

Like most you’d probably just consult the Miele manual:

The dishwasher is set at the factory for a hardness level of 0.2 – 0.7 mmol/l (1- 4 °d )” and “Mains water with a hardness level higher than 0.7 mmol/l (4 °d –German scale) needs to be softened.

– The water softener requires reactivation salt.
– The dishwasher must be programmed for the water hardness in your area.
– Your local water authority will be able to advise you of the water hardness level in your area”.

Now, unless you have a background in chemicals, this explanation is ‘as clear as mud’.

At this point, most people would look elsewhere for help. First stop probably the Sydney Water website. Unfortunately it’s also not very helpful for explaining what water hardness is, let alone what value you need for your Miele Dishwasher!

Here’s a much simpler explanation
In case you ever notice the salt light on in your Miele dishwasher, don’t despair. Here’s a quick explanation of what to do.

From my work and testing in certain service areas in Sydney, the average water hardness is 51 ppm. This value converts to 0.51 mmol/l, which is the value (mmol/l ) given by Miele in its operating manual (you’ll find this in the Before Using for the First Time section). As an aside, if you’re German, this basically relates to a hardness of 3 °d.

So, you need to set your Miele Dishwasher to setting 3. And you do not need salt.

You’ll see that while the manual says “mains water with a hardness level higher than 0.7 mmol/l (4 °d –German scale) needs to be softened”, this only applies to the areas I have listed on my website.

How did I arrive at this value?
A basic calculation. Your area’s water hardness (for Sydney Water) is worked out by calculating:

– ppm divided by 100.

This gives you mmol/l. Then, check the manual for the correct settings in German scale (°d). Simple.

Where did I source my data?
First, I used Choice magazine, which tests its water supply weekly (they’re located in Marrickville, which has an average water hardness value of 47 ppm). I also used my own water hardness strip tests and the Sydney Water website for Treatment Plants in the inner west, eastern suburbs and CBD. Interestingly, the water in all of the areas where my customers are located comes from the Kurnell Desalination Plant, which feeds in at the Potts Hill Plant and has the following hardness values:

45-57 ppm 0.45 -0.57 mmol/l 2 – 3 deg (German scale)

What’s more, it’s soft water according the German/European standard (2007) and is soft up to 8.4°d German scale.

Now for the issue of dishwasher salt …. Actually, I think that’s enough information for one day. You’ll find more about that in my next blog, so stay tuned.

Still unsure?
If you’re still a little unsure about water hardness, don’t worry, I’m here to help. Simply email me. I’ll be glad to hear from you. And if I’ve solved your problem, that’s great!

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