Introduction
When a water softener removes calcium and magnesium from hard water, it replaces them with sodium. The amount of sodium added is small — a 240ml glass of softened water from a 300 ppm hard water area contains roughly 11mg of sodium — but the question of whether softened water is safe to drink comes up in almost every installation conversation.
The answer for most people is yes, with a sensible caveat for specific groups, and a practical solution that most UK homes adopt as standard.
How Much Sodium Does Softening Add?
The sodium content of softened water depends directly on the original hardness. The higher the hardness minerals removed, the more sodium replaces them. As a rough guide:
- Soft water area (100 ppm hardness): softening adds approximately 4mg of sodium per 240ml glass
- Moderately hard (200 ppm): approximately 8mg per 240ml glass
- Very hard (400 ppm): approximately 15mg per 240ml glass
For context, a slice of bread contains around 150 to 200mg of sodium. The amount added by drinking softened water is genuinely small relative to normal dietary sodium intake.
Is Softened Water Safe for Most Adults?
The UK Drinking Water Inspectorate (DWI) and most NHS guidance state that softened water is safe for healthy adults to drink. The sodium levels resulting from domestic water softening fall well within acceptable safety limits for people without specific dietary restrictions.
The World Health Organisation recommends that drinking water sodium should ideally not exceed 200mg per litre. Even in very hard water areas, sodium from a correctly operating domestic softener stays well below this threshold in the softened output water.
Who Should Be Cautious
Two groups where softened water for drinking merits more thought:
- People on a medically supervised low-sodium diet: If a GP or consultant has specifically advised limiting sodium intake due to heart disease, kidney disease, or hypertension, the additional sodium from softened water is worth discussing with them. Most will advise using an unsoftened tap for drinking and cooking.
- Babies and formula: NHS guidance recommends that water used to make up infant formula should not be softened. The sodium levels, while safe for adults, are too high for young infants whose kidneys cannot process excess sodium effectively. This applies until babies are established on solid food and drinking ordinary water.
The Standard UK Solution: An Unsoftened Drinking Tap
The practical answer most UK households adopt is straightforward: leave one cold kitchen tap connected to the unsoftened rising main. This tap — usually the main cold kitchen tap — delivers hard water directly from the supply for drinking and cooking. The rest of the house runs on softened water for all other purposes.
This configuration is standard practice in the UK and is built into most water softener installations as a matter of course. It costs nothing extra and requires a simple bypass in the installation pipework. If you are getting quotes, confirm this will be included — any reputable installer will do it automatically.
Does Softened Water Taste Different?
Many people notice a slight difference in the taste of softened water — often described as slightly flatter or silkier than hard water. Some prefer it; others prefer the mineral taste of hard water. Neither perception is wrong.
If you find softened water tastes of chlorine or has any off-note, that is not from the softening process — it is from the mains supply itself. An under-sink activated carbon filter on the drinking tap (which can be the unsoftened tap) addresses chlorine taste effectively at low cost.
Frequently Asked Questions
Yes, for healthy adults. The sodium added by domestic water softening is well within safe limits for the majority of people. NHS and DWI guidance does not advise against adults drinking softened water. The exception is people on medically supervised low-sodium diets and babies under formula — both should use unsoftened water.
No. NHS guidance recommends that water used to make up infant formula should not be softened. Young infants cannot process the elevated sodium levels safely. The practical solution is to leave the cold kitchen tap unsoftened and use that water for making up formula and for any other infant drinking water.
It depends on your original water hardness. In a moderately hard water area (200 ppm), a 240ml glass of softened water contains roughly 8mg of sodium. In a very hard area (400 ppm), around 15mg per glass. For context, a slice of bread contains 150 to 200mg of sodium — so the contribution from softened water is small for most people.
Yes — ion exchange removes calcium and magnesium from the water. These are beneficial minerals, though most UK dietary calcium and magnesium comes from food rather than water. If this concerns you, an unsoftened drinking tap preserves access to mineralised water for drinking and cooking while the rest of the house benefits from soft water for appliances and cleaning.
Yes, as standard practice. An unsoftened cold tap in the kitchen — fed directly from the rising main, bypassing the softener — is included in virtually all reputable UK water softener installations. It costs nothing extra and means you always have access to unsoftened water for drinking, making tea, and cooking without needing to buy bottled water.
Conclusion
Softened water is safe to drink for most adults. The sodium level added by domestic softening is low, well within WHO guidelines, and negligible in the context of a normal diet. The practical standard for UK households is to leave one kitchen cold tap unsoftened — preserving access to hard water for drinking and infant use, while the rest of the house benefits from soft water.
If you are in a specific at-risk group — medically supervised low-sodium diet, or making up infant formula — use the unsoftened tap for those purposes and you have nothing to worry about.
Written by water-softener-quotes · Content Team