Tap, Filtered or Rainwater: The Best Water for Plants
Most houseplants thrive on plain tap water, but some sensitive species need filtered or rainwater. Learn what's in your water, which plants are fussy, and how to treat tap water.
The water you pour matters more for some plants than others. The vast majority of houseplants do perfectly well on ordinary tap water, and switching to bottled or distilled water is usually unnecessary expense. But a handful of sensitive species react to the chlorine, fluoride, and dissolved minerals that municipal water can contain, browning at the tips when watered with straight tap water.
This reference explains what's actually in tap, filtered, distilled, and rainwater, which plants are sensitive, and simple ways to make tap water safer without buying anything. Knowing your own water is the first step, since hardness and treatment vary widely by region.
What's in tap water
Municipal tap water typically contains chlorine or chloramine for disinfection, sometimes fluoride, and dissolved minerals like calcium and magnesium that determine hardness. For most plants none of this is a problem at the concentrations used in drinking water, and tap water's trace minerals can even act as light nutrition.
The two ingredients that cause trouble for sensitive plants are fluoride and chloramine. Chlorine evaporates if water sits out overnight, but chloramine, used by many utilities now, does not dissipate, and fluoride stays in solution regardless. Hard water also leaves mineral crust on soil and pots over time.
Which plants are sensitive
Fluoride-sensitive plants include dracaenas like the dragon tree and corn plant, spider plants, calatheas and prayer plants, and many palms; these show brown, scorched leaf tips when watered with fluoridated tap water. Carnivorous plants like Venus flytraps are the most sensitive of all and should only get distilled or rainwater, since they evolved in mineral-poor bogs.
If a normally healthy plant develops persistent brown tips despite correct watering and humidity, water quality is a likely culprit. Switching these species to filtered or rainwater often clears the problem within a few months of new growth.
Filtered, distilled, and rainwater compared
Filtered water from a basic carbon filter removes chlorine and improves taste but leaves most minerals and fluoride behind; reverse-osmosis filtration removes nearly everything. Distilled water is essentially mineral-free and safe for the fussiest plants, but contains no nutrients, so plants relying on it benefit from light, regular fertilizing.
Rainwater is many growers' favorite: it's naturally soft, slightly acidic, free of chlorine and fluoride, and free. Collect it away from metal or treated roofs, and use it within a week or two to avoid algae and stagnation. For most homes, a mix of rainwater for sensitive plants and tap for the rest is the practical approach.
Simple ways to treat tap water
If your utility uses chlorine, letting tap water sit out uncovered for 24 hours lets it off-gas, making the water gentler. This does not work for chloramine, which requires a carbon filter or a dechlorinating product to remove. Check your water utility's report to learn which disinfectant they use.
Room-temperature water is easier on tropical roots than cold, so let water warm up before pouring regardless of its source. For hard water leaving mineral crust, flushing the soil thoroughly every month or two clears built-up salts and minerals.
- Let chlorinated tap water sit out 24 hours so chlorine off-gasses
- Use distilled or rainwater for carnivorous plants and fussy calatheas
- Always bring water to room temperature before watering tropicals
- Persistent brown tips with good care often point to water quality
FAQ
Is tap water bad for houseplants?
For most houseplants, no; ordinary tap water is perfectly fine. The exceptions are fluoride-sensitive plants like dracaenas, spider plants, calatheas, and palms, plus carnivorous plants, which can develop brown tips from the fluoride and minerals in tap water. For those species, filtered, distilled, or rainwater is a better choice.
Does letting water sit out overnight help?
It helps only if your utility uses chlorine, which evaporates when water sits uncovered for about 24 hours. Many utilities now use chloramine instead, which does not dissipate this way and requires a carbon filter or dechlorinating product to remove. Check your water report to know which you have.
Is rainwater really better for plants?
Yes, for many plants. Rainwater is naturally soft, slightly acidic, and free of the chlorine, fluoride, and excess minerals found in tap water, which makes it ideal for sensitive species. Collect it from a clean surface, store it covered for no more than a week or two, and bring it to room temperature before using.