Pilsen water - Ca too low?

I understand that the mash generally requires at least 50 ppm of Ca.

I further understand that Pilsen water only contains around 10 ppm.

My water in Singapore has very low mineral content (also about 10 ppm of Ca in it).

When I was brewing my latest BoPils, I was very tempted to put in a couple of grams of Calcium Chloride to reach the 50 ppm of Ca (based on my calculation with the Bru'n Water Excel calculator); however, I decided against it in order to "maintain authenticity".

I have a question to the water gurus here - do Pilsen brewers adjust their water to reach that 50 ppm Ca or do they somehow "get away" without it? If it's the latter - is the Bohemian lager yeast more resistant to Calcium deficiencies?

Supposedly, the extensive decoction method extracts more trace minerals from the grains.

I have similar water to pilsen in portland, or, usa, and have brewed pilsners with triple decoctions, and no calcium additions (just acid to adjust mash ph) and the beer ferments fine, with proper attenuation, and no off flavors.

The 50 ppm calcium requirement is a myth. Calcium is supplied at sufficient concentration for yeast health by the malt. The water does NOT need any additional calcium for yeast or the fermentation. HOWEVER, there are reasons that you might want to include calcium in your brewing water. For ale brewing, the extra calcium helps with yeast flocculation and clearing the beer. If you lager or filter your beers, that won't be a factor. Another reason is to get oxalate out of your wort before it gets into your beer. Oxalate is the precursor for beerstone. A final reason is that you might want ions like chloride or sulfate in your beer for their flavor effects and adding them with calcium is a decent way to go.

For lager brewing, it is actually a very good idea to brew with very low calcium since those yeast prefer low calcium conditions.

Thank you very much for an in-depth explanation - I really appreciate it.

I further would like to thank you for the Bru'n Water application - I am big fan and use it for every brew