Updated: Jul 2
The German independent testing institute and publisher 'Stiftung Warentest" tested 32 classic mineral waters conclusion: water from German supermarkets is usually good.
They provided the grade “very good” eight times, including the 6 discount retail brands from Lidl, Penny, Rewe, Norma, Aldi Süd and Aldi Nord.
The 6 German Discounter brands:
Lidl Saskia Classic (Source Läningen)
Penny Classic ("Forest Source")
JA! Classic ("Quintus Source")
Aldi Nord Quellbrunn Classic
Aldi Süd Quellbrunn Classic
Norma Surf Classic
The 2 German national brands:
Vilsa Naturfrisch Classic
The mineral water from discounters Lidl, Penny, Rewe and Aldi usually costs 0.25 euros (US$ 0.27) per 1.5 liter PET bottle, which corresponds to the already mentioned liter price of around 0.17 euros (US$ 0.18)
Well-known national branded products such as Gerolsteiner, San Pellegrino, Residenz Quelle and San Benedetto scored "good". However, they are also very expensive at around 0.50 euros (US$ 0.53) per liter.
Some time ago, 'Stiftung Warentest' also examined butter, a discounter product was one of the test winners.