For me, an ounce of prevention is better than a pound of cure when it comes to limescale. Yes, I know you can descale your machine, but why head down that path if you don't need to? Removing limescale tends not to improve the life of the seals in your machine, it is time consuming, and generally a pain in the butt.
Note that what I'm about to write doesn't specifically address the highly technical debate about the optimal composition of water for espresso, or indeed coffee in general. This has been addressed by Jim Schulman online already, fully supported with a detailed discussion of the chemistry at work. His recommendation for those of us wishing to just make some great coffee and get on with our lives (as opposed to embark on a doctorate in Chemistry, or just pontificate in general) was to use Volvic water. Readily available in numerous countries, relatively economical, won't scale your machine, and an acceptable taste for coffee (although not optimal in my opinion). So, Volvic provides a practical solution, which we thoroughly endorse.
Volvic brings the added benefit of standardisation, reducing a variable from the coffee equation. This allows you as a customer to know that we have optimised the roast using Volvic water and to use the very same water in your machine, eliminating a significant variable from the equation. This makes it easier for you to taste the coffee the same way as we did. Given that a cup of coffee is probably something like 98% water we think this is quite important.
Back to Brita. Last time we looked at Brita's offerings probably back in 2007, in domestic filtration at least, they were curiously silent on the suitability of their filters for the reduction of removal of limescale. This may have been an oversight on Brita's part, but rightly or wrongly the cynic in us tends to assume that if it isn't mentioned it isn't suitable. From looking at Brita's website this morning it is clear that their products are now specifically intended to reduce limescale to acceptable levels, and indeed they are looking to meet the needs of the speciality coffee consumer.
It's a long story, but what bought us 'back to Brita' was a call from a man in London who had purchased a Maximatic in Switzerland in 2010 and managed to limescale the daylights out of it in a few months. We made a house call and discovered that a machine that had supposedly received very little use had sufficient limescale deposits to result in the stainless steel ball valve in the base of the reservoir tank no longer sealing, causing the machine to leak.
The man was very cross at us, bizarrely as he wasn't a customer, saying he had a Jura machine before the Maximatic and that that Jura had a built in filtration system, which addressed the limescale issue among other things. He told us we shouldn't be selling a machine in the UK unless it had a built in filtration system to address the limescale issue and was generally lacking in Christmas spirit.
A tricky one as we had no previously dealings with the man, and if you have dealt with us you will know how we bang on ad nauseum about the importance of protecting your coffee equipment from limescale with the use of Volvic. We were also quite keen to introduce the man to Londinium espresso as he was using Monmouth coffee and never knew of our existence until he needed his Maximatic issues addressed in the UK.
While London water is high in limescale we didnt think it was high enough to be consistent with the extent of scaling that had occurred in the limited number of times is was claimed the machine had been used. We have our suspicions that some of the contents of the bottles of Evian water in the house were making their way into the machine, which would account for the extent of limescale in such a short period of time.
The point we are trying to illustrate is dont assume that bottled waters are suitable for espresso machines. Most aren't. The 'purity' halo that surrounds bottled water is a marketing triumph, but does not equate to suitability for espresso machines, and indeed any household appliances that are heating water (kettles, irons, etc). It is further complicated by the fact the hard water makes for good espresso, you just dont want this hardness to come from high levels of calcium carbonate otherwise you will experience limescale in your machine.
In the above case we recommended that Volvic be used, but this guy didn't feel it was acceptable that a machine had to use bottled water (despite the fact we are pretty sure he was using Evian, but wouldn't admit it). We rang another customer of ours who has a Cremina (and notoriously particular about his coffee) and he said he was using a Brita filter jug and had not seen any limescale in his Cremina after more than 12 months of using it all day every day (he works from home).
The Maximatic runs at higher boiler temperatures than the Cremina, and so it will be more vulnerable to limescale, but we thought a Brita filter would probably be suitable. We rang the Olympia factory in Switzerland to get their thoughts on the matter. They said yes, they were using the Brita aqua aroma crema model of water filter with much success. This was not a Brita product that I was aware of, I think it is relatively new to market or perhaps I just haven't been keeping up, so they sent me one. This arrived a couple of days ago. It is a product specifically developed to meet the needs of owners with domestic espresso machines that have a reservoir. It fits into the base of the reservoir in the Maximatic, being designed to work on a suction basis. It does not of course filter the water that goes into the boiler of the machine.
For the boiler you would need to continue using Volvic or filter your water using a Brita water jug. This makes more sense than it sounds, particularly for those of you who don't steam a lot of milk. At the moment we find ourselves hauling rather a lot of Volvic water home from the supermarket. The novelty wears off fairly quickly if you are doing this on foot, as you are likely to be doing if you live in central London, or indeed the centre of any large city. Critically, I think you may find the Brita filtration gives you a better tasting espresso than Volvic water, but this is merely an untested hypothesis at this stage.
We will get this out and learn how to fit it to our Maximatic demonstration machine when we have a moment, and we might even perform some Volvic versus Brita filtered London tap water to compare results. I suspect on a taste basis the Brita will probably beat the Volvic (my wife purchased a kettle with a built in Brita filter this week and when this water is used with a Swissgold filter the results are astounding). That kind of gourmet coffee experience, but delivered with ease and simplicity, completely encapsulates what Londinium Espresso is all about. Electric kettle with a built in Brita filter; add water and set to boil, grind coffee into KF300 Swissgold filter, sit KF300 Swissgold filter on coffee cup, water comes to boil, add to KF300, wait a minute or two; gourmet coffee. Simple! Lift off KF300 Swissgold filter, wash under hot tap, dry, place back in cupboard, sit down and enjoy coffee. Perfect coffee for people with busy lives. No poncing about.
The only thing to remember if you chose to go down the filtered water path is that the filter becomes progressively ineffective as it retains more and more contaminants. It is easy to forget to change the water filter as often as it needs to be. Brita address this on their water jugs with the addition of a 4 bar LED system that drops by one bar a week (i.e. time driven). This is a bit crude in that it is not driven by the volume of water processed by the filter, but that kind of metering is presumably more expensive to add to a consumer product. I suspect Brita manage to convince people to change the filter much more often with a time driven system too, as it works independent of how much you actually use the product, which is ideal for Brita.
Please understand this is not a plug for Brita. I am sure there are other products on the market the perform the same task to an equal of better standard, and most probably cheaper. Brita is simply a well known international brand that you are likely to be able to relate to and compare with other brands available where you live. We are not associated with, or affiliated to, or receive any kind of compensation, reward, benefit, or credit from Brita in anyway whatsoever.
I didn't find the Aqua aroma crema the easiest product to locate on the Brita website, so if you are interested here is the link. Note this page also contains the more informative pdf documents on the left had side. These contain the detailed product information that you are looking for.
http://www.brita.net/uk/professional_details.html?L=1&p_id=272&ps=crema