Tap water, rainwater, or distilled — does the water you use to water Lithops actually matter?

Lithops evolved on rainfall-fed quartz fields where the water is naturally soft, slightly acidic, and free of dissolved chlorine. They tolerate harder water than that, but only up to a point. Once total dissolved solids rise above roughly 300 ppm or pH stays consistently above 7.5, the fibrous roots start to function less efficiently and you see slow, hard-to-pin-down decline — pale window, slow split, no flower.

If your municipal water is soft (typical of granite-bedrock cities) and chlorinated rather than chloraminated, it is fine. Let it sit in an open container overnight to off-gas the chlorine before watering.

Hard water (limestone-bedrock cities, anything with visible kettle scale) accumulates in the mineral mix over time. You will not see damage in year one; by year three you have a salt crust on the top-dressing and a noticeably less responsive plant. Alternate with rainwater or flush deeply once a season.

Chloraminated water does not off-gas. If your utility uses chloramine, you need a carbon filter or a switch to rainwater for sensitive plants.

Rainwater is the gold standard — soft, slightly acidic, free of treatment chemicals. Collect from a clean roof, store covered, use within a few months.

Distilled or RO water is fine and what most serious collectors use indoors. It contains effectively zero minerals, so if you fertilise (rarely, very dilute), you are starting from a known baseline.