We have a Bosch Filtrino water heater for heating water for tea & coffee, as it heats 250ml of water at a time, by induction, saving energy compared with a kettle's power requirements.
There are two indicators to the bottom-left of the device. The upper indicator lights wen a certain number of measures have been dispensed, indicating that the filter probably needs changing. This light has been lit for a few months, as we promptly lost the manual and don't know the process for extinguishing the light. The lower indicator is the relevant one here, though.
It lit a few weeks ago. Looking online, I see that it means that the device needs to be de-scaled. We live in a very hard water area, so it's no surprise that de-scaling is needed, and our previous water heater had to be thrown away after lexcessive limescale build-up clogged all the internals and the motor burned out.
So, we're aware that we need to perform regular maintenance. As I mentioned, we lost the manual. So, we didn't bother doing it.
Anyway, it stopped working last week. I decided to bite the bullet and find a manual online that would tell me how to de-scale the device.
After perhaps 30 minutes searching, I finally found the manual. It wasn't easy to find. The manual had a whole section on how to de-scale the device.
I read the instructions ... turn the device off, empty the water chamber, refill it to a "de-scaling mark" with limescale-removing solution, turn the device on while holding the "power" button down, and wait 10 seconds, until the solution is passed through the device. When completed, run 3 tanks of water through the device to make sure all the de-scaler is removed.
Ok, all sounds straightforward.
Until I reach the "limescale-removing solution". I double- and triple-check the instructions, and they read "use the instructions for your limescale remover to produce the correct strength of de-scaling solution". I read the instructions on the bottle of "Limelight" that I have. It just says "Safe for use throughout the bathroom and the kitchen. Can be used neat or diluted". this presents me with a dilemma. Should I use it neat, pouring the whole 500ml bottle of limescale remover into the water heater, or should I dilute it?
I decide that I should dilute it, because I can always retry the process if it doesn't work very well, adding more limescale remover until it works properly. So I add a couple of long squirts of the limescale remover to 500ml of water, and begin the process.
The water doesn't flow very fast, but it DOES flow. After it's finished, I can see some flakes of limescale in the jug, but the "please de-scale me" light is still lit, so I pour the waste water back into the chamber and try again.
The water flows a little faster this time, with more flakes, but the light is still lit. I try again.
The water flows faster still, with a cloud of limescale in the waste, but the light is still lit. I wait for it to settle in the jug before decanting into the chamber and trying again.
The water is almost back to its original flow-rate, with more cloudy waste water. Eventually, after perhaps 10 of these run-throughs, the "please de-scale me" light is extinguished.
Folling instructions, I run 3 tanks of water through the device. I run another three tanks, just in case.
I heat water for a coffee. It tastes of de-scaler. I pour the coffee away.
I run another three tanks of water through the device. No change - still tastes like de-scaler.
I run tanks of water through the device for hours. When I'm finally fed up with this, I make coffee for Doris and myself. Doris complains that it tastes of de-scaler, but dammit - I'm going to drink it anyway.
For the next week, I have instant coffee and I have to brew filter coffee for Doris. She eventually relents, saying that the taste is almost gone. This leaves me with one question: if limescale remover is safe to use throughout the bathroom and kitchen, how toxic is it going to be if drunk?