@jecka, it's not safe for soil. but I grow in 60% coco + 40% perlite in airpots so its a very light medium with a lot of runoff. Its somewhere between soil and hydroponics in terms of water needs.
@jecka, I used a drip watering system to water the plants. Had to refill the reservoir every 3 days. The reservoir holds about 20l of water.
So 20l/3 days = 6.6l per day
6.6l per day for 3 plants so about 2.2l a day per plant rounded down to 2l.