Carnivorous plants are sensitive to the minerals dissolved in water, so the first question for most new growers is whether their tap water is safe. Type the TDS (total dissolved solids) reading of your water below and the checker compares it with the limits published by the International Carnivorous Plant Society (ICPS), botanist Barry Rice and the nursery Sarracenia Northwest.
How to Get Your Reading
The ICPS lists four ways to find your number: ask your city, ask your water company, look at a well test, or measure the water yourself with a TDS meter. With your own meter you can also test each new batch of water, including the output of a home reverse osmosis unit.
Where the Limits Come From
| Limit | Who sets it | What it is for |
|---|---|---|
| Below 90 ppm | ICPS Venus flytrap guide | Tap water you can use for carnivorous plants |
| Below 80 ppm | ICPS seed germination guide | Water for germinating seeds |
| Around 50 ppm or lower | Barry Rice, Sarracenia FAQ | The usual target for purified water |
| Below 50 ppm | Sarracenia Northwest | Tap water for Sarracenia |
The sources do not agree on one number, which is why the checker shows a middle zone. Reading them side by side, 50 ppm is the level every source accepts, 80 ppm is the ceiling for seeds, and 90 ppm is the point where the ICPS says to stop using tap water. If your reading sits between 50 and 90 ppm, adult plants may cope, but the stricter sources would still steer you to purer water.
If Your Water Is Too Hard
- Switch to purer water. The ICPS recommends distilled, reverse osmosis or clean rain water once tap water is above 90 ppm. Sarracenia Northwest calls all three excellent choices.
- A normal filter is not enough. The ICPS points out that filtering will not remove dissolved salts.
- Boiling is not distilling. Barry Rice stresses that boiled water is not the same as distilled water, so a kettle will not fix hard water.
- Read the label. Rice warns that bottled water labelled only as “drinking water” or “spring water” tells you nothing about its mineral content.
- Test a home RO unit. Rice suggests testing the water from a cheap reverse osmosis unit every three months.
Related Guides
Sources
- International Carnivorous Plant Society, Dionaea (Venus flytrap) growing guide [carnivorousplants.org/grow/guides/Dionaea]
- International Carnivorous Plant Society, Seed germination [carnivorousplants.org/grow/propagation/seedgermination]
- Barry Rice, Carnivorous Plant FAQ: water [sarracenia.com/faq/faq3380.html]
- Sarracenia Northwest, Sarracenia care [growcarnivorousplants.com/sarracenia-care]
This tool is editorially reviewed and its limits are checked against the cited sources. Last reviewed: October 2026.