Connection between Hard Water and Urinary Crystals in Cats
There are strong indications, based upon a study carried out by a large pet medical insurer, that there is a connection between urinary tract health problems, particularly crystals in the urine, and hard water. I think that this is quite significant if the connection can be confirmed. Not long ago Eliza Black-Taylor wrote about the possibility of tap water causing cat health problems. This is a follow-up to that article.

Struvite Crystals. Photo: Cuyahoga Falls Veterinary Clinic
The leading provider of medical insurance for dogs and cats, Trupanion, released a report on seventh April which identified a possible connection between urinary health problems amongst pets and hard water ratings in America per the Environmental Protection Agency (EPA).
For example, in Tampa, Florida where the water is said to be extremely hard, they found that they were paying out 10 times as many claims for crystals in urine amongst male cats compared to payments made in respect of male cats living in soft water areas.
The insurance company says that hard water contains more calcium and magnesium. Also hard water can cause health problems in humans. Male cats living in “extremely hard water” areas suffer a much higher incidence of urinary health issues, particularly crystals found in urine which is described as “crystalluria”. Overall they were three times more likely to have urinary complications compared to male cats in areas where the water was less hard and described as “slightly hard” or “hard” or “very hard”.
With respect to cats, interestingly, they discovered that male cats are 1.5 times more likely to be the subject of a claim for medical treatment with respect to urinary health issues than for female cats.
With respect to dogs, owners of female dogs are 2.5 times more likely to submit a claim for urinary conditions compared to owners of male dogs.
Overall the urinary tract conditions allegedly affected by hard water include: urinary tract infections, cystitis, urinary obstructions and, as referred to above, crystalluria.

Hardwater ratings in USA (EPA)
The map above shows visitors where hard water is found in America. “Extremely hard” water is found in Miami, Chicago, Detroit, Cincinnati, Minneapolis, to name some cities.
Sometimes urinary tract problems can be very expensive to treat. In one case a cat required extensive surgery at a cost of $11,600.
The Chief Veterinary Officer at Trupanion made the point that a further study is required to confirm the connection between hard water and crystalluria. However, should this connection be confirmed, which appears to be likely, then it must have a significant impact on decision-making by pet owners with respect to the quality of drinking water in their households. It would, on the face of it, mean pet owners seriously considering softening the water in their homes across large areas of America because the impact of hard water, on the basis of this initial cross-referencing, on a cat’s health is substantial and it cannot be ignored by any responsible cat owner.
Note: the top picture is for illustrative purposes. I don’t know if struvite crystals are caused by hard water.