The short answer to the title question is no, a cat should not drink softened water. However, this is not a black and white situation and I am yet to find a definitive answer regarding cats.
As for humans, in the UK, the British Water Code of Practice as referred to in the Water Supply (Water Fittings) Regulations, 1999 recommends that a mains water tap should be fitted that bypasses an ion-exchange water softener and which is supplied from mains water. Water from the mains in the UK meets very stringent standards and is often better than bottled water bought at the supermarket.
As it is recommended that humans drink mains water rather then softened water, it is reasonable to presume that the same recommendation applies to companion animals. A point worth making is that cats get a lot of their water from their food if it is wet cat food. A low intake of tap water means it has less of an impact on their health.
Water softeners, that use salt, increase the amount of sodium in the water. The salt in ion exchange water softeners is used to regenerate the “ion exchange resin” in the device. This keeps the machine working. The ion exchange resin removes the minerals in the water that makes it hard: calcium and magnesium.
By how much is the sodium content of water increased by an ion exchange water softener? I’ll answer by referring to the daily recommended allowance of salt for humans in the UK. A litre of milk contains 25% of the daily allowance of sodium (salt equivalent of 1.5 grams). A litre of softened water contains 6% of the daily allowance. You can see that it is a small amount (0.35 grams equivalent of salt).
One important reason why an ion exchange water softener should be bypassed for drinking water is because powdered milk for babies has sodium in it already and to increase that level through softened water is bad for a baby’s health because they have a poor tolerance to sodium.
Although sodium is an important mineral for cats – it is used for muscle and nerve function – The American Society for the Prevention of Cruelty to Animals ® state that “foods that are inappropriate for pets” include salt. Salt is sodium chloride. I am not sure this is significant in relation to this article but it does confirm that salt in excess is not good.
As an ion exchange water softener uses salt and results in an increase in sodium in water it would seems wise and safe to plumb-in a bypass to the device that supplies tap (faucet) drinking water for your cat’s water bowl.
One final and important point, Elisa, a guest writer asks: Is water making your cat sick? This is about the contents of tap water that might not be good for your cat. The quality of tap water is dependent on where you are.
Click here to see a list of articles on water and cats.
- Department of the Environment, Food and Rural Affairs, London (Defra)
- Department of Health, London
- The Water Regulations Advisory Scheme, Oakdale, Gwent