In our city the water is very hard - 19.3 dH according to one of my lab tests. During the first year after the home we live in was constructed we didn't use any water softening system and a few problem came as a result:

  • Hot water tank outlet got clogged with the sediment resulting in a massive hot water pressure drop
  • Hot water circulation pump got clogged up and has almost no effect
  • Hot water automatic over-pressure valve is clogged and leaking since it can't fully close
  • And of course a ton of mineral deposits on sinks, bathroom walls and taps

Disclaimer: this post documents my experience as a consumer and is not a professional advice. Things may wary based on behavior of a particular unit and water contents in your area.

I took a cursory look on the options available and picked GENO-K4 without much research since it didn't require salt or maintenance and had no risk of water contamination through the salt tank. I didn't find any user reviews for it though. Should have changed my mind at that point.

Since I didn't do my homework, I was under a wrong impression that GENO-K4 removes the minerals from the water. It does not. Instead, calcium crystals are formed to prevent them from precipitating in the pipes.

From my experience, if the processed water dries on your tap or sink, the result would be about the same as without this system.


3258 EUR later the system was installed and working.

According to the manual, it has to process 10m3 of water in order to become fully operational and I did all my tests after that.

Experiment with a kettle

I think the system prevents deposition of minerals in the heating systems. Here's a little experiment with a kettle, cleaned with citric acid before each attempt:

Here's how it looks after boiling 1 liter of unprocessedwater. Notice the white flakes in the water and spots on the heating plate. Need a kettle with fine filter to get a drinkable tee:

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Boiling water that was processed by GENO-K4 shows no signs of mineral deposits:

Yellow water: don't set the water hardness too high

You control the device by setting the carbon water hardness, which is measured with a supplied testing kit. This is a different thing than your standard water hardness.

Technician initially measured 15-16 dKH but I re-measured a few times and had more like 18-19 dKH. I dialed in 18 dKH. Some weeks later, the tap water started to show yellow tint and I also saw a major increase in nitrite contents in the water.

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| Left: water from the pipe. Right: water from the tap. This is just one pair of test results and can be incorrect. |

Another technician came in to check this and dialed in 15 dKH after measuring the incoming water a few more times. About a week later, the water color returned to normal.

I'm still not sure which value is right, but since we prefer transparent water over yellow, we didn't change the setting since :-)

Mineral deposits on sinks and taps

I didn't notice any improvement here.

Unclear which hardness to set on appliances

Our dishwasher and the coffee machine also have the water hardness settings with affects how often they request to be cleaned. With GENO-K4 installed, I have no idea what to dial in there.

According to the lab test, the water hardness drops to 16.2 dH in the tap water. When I measure tap water with this kit, I still get ~19 dH.

At the same time, the kettle experiment shows that there's a major decrease in deposits which is likely equivalent to water being soft.

Power usage

The device uses about 0.8 kWh per m3. Electricity price is 0.3 EUR per kWh. For a family using 200m3 a year, additional spending would be 48 EUR / year.


The system does work but does not appear to help in cases where water is left to dry.

If I knew all this from the start, I'd just take the standard salt-based water softening system and save a ton of time and money - and have less sinks and taps to clean.

I hope to sell GENO-K4 at some point, but this is a major undertaking I'm not ready for at the moment.


I sold the GENO-K4 for 500 EUR and installed Grünbeck softliQ:SC18 instead.