Can I drink softened water?

This is the question everybody asks when a softener is being considered, and the answer is more nuanced than either 'perfectly fine' or 'never'. The chemistry is straightforward: ion exchange does not remove anything without putting something back, and what it puts back is sodium. How much depends entirely on how hard your water was to begin with.

Safety

Step by step

1. Understand the exchange.The resin swaps calcium and magnesium ions for sodium ions. The harder the incoming water, the more calcium is removed and the more sodium is added. In a soft area the addition is trivial; in a very hard area it is not.
2. Work out roughly what that means for you.The sodium added is proportional to the hardness. Find your water hardness figure, and the softener manufacturer or installer can tell you what sodium level the softened water will carry. That is the number to compare against drinking water standards and any medical advice you have.
3. Keep a hard water tap and use it.Every correctly installed softener leaves at least one tap on the unsoftened supply — conventionally the kitchen cold tap, which is also the one always fed directly from the main. Use it for drinking, for filling the kettle, for cooking and for filling pet bowls.
4. Never use softened water for infant formula.This is the clearest restriction. Formula is made up to a precise composition and the added sodium is not appropriate. Use the hard water tap or bottled water suitable for infants, following the formula manufacturer's guidance.
5. Take medical restrictions seriously.Anyone on a low-sodium diet for blood pressure, kidney or heart reasons should use the hard tap for everything they drink and cook with, and should mention the softener to whoever manages their care.
6. Consider plants and fish separately.Softened water is not ideal for houseplants over the long term because of the sodium, and it is unsuitable for aquariums, which need controlled water chemistry. Use the hard tap for both.
7. Check the installation is actually correct.If you have moved into a house with a softener, check whether the kitchen cold tap is really on the hard supply. Run both and taste them, or test with a hardness strip: the drinking tap should read hard. Installations that softened everything do exist.
8. Know that a separate drinking tap is an option.Where the plumbing makes retaining a hard kitchen tap awkward, a small dedicated drinking water tap plumbed to the unsoftened main is a common and inexpensive solution.

Tips

• Test the kitchen cold tap with a hardness strip after any softener installation. It is the two-minute check that proves the hard tap was actually left hard.
• Label the taps in a household where anyone is on a sodium-restricted diet, particularly if there are carers or visitors.
• Softened water makes noticeably better tea and coffee for some people and worse for others — that is taste rather than safety, and the hard tap gives you the choice either way.
• If a softener installation left no hard tap at all, that is worth correcting rather than living with.

Questions people ask