Is Your Cat’s Water Making Them Sick? The Hidden Dangers of Tap Water for Cats


Crystals in a cat’s urine can be a concerning finding for pet owners. These crystals can be painful for cats and lead to the development of stones in the urinary tract. The main types of crystals that form are struvite and calcium oxalate. While genetics can play a role, diet and water intake are considered the main causes of crystal formation. Some claim that tap water, with its mineral content and high pH, contributes to crystal development in cats. This article will examine the link between tap water and urinary crystals in cats. It will cover the causes, risks, and prevention of crystals to help owners make informed decisions about their cat’s health.

What Are Crystals in Cats?

Crystals in cats refer to the formation of minerals in the feline urinary tract, which can lead to bladder stones (uroliths). These crystals are often composed of struvite (magnesium ammonium phosphate) or calcium oxalate 1. Struvite crystals form in alkaline urine and used to be the most common type in cats. With changes in commercial cat food formulation, calcium oxalate stones are now more prevalent 2.

Crystals form when there is an imbalance in the chemical makeup of a cat’s urine. When the minerals crystallize, they can aggregate into larger bladder stones. These stones irritate the bladder lining and urethra, often causing symptoms like frequent urination, blood in the urine, and straining to urinate. Left untreated, crystals and stones can completely block the urinary tract, leading to potentially fatal kidney damage.

Causes of Crystals

There are several factors that can contribute to crystal formation in cats.

The mineral content of a cat’s urine is one factor. Certain minerals like struvite, calcium oxalate, urate, and cystine are more likely to crystallize and form stones when concentrated in urine ( Cats with a genetic predisposition may produce urine with higher concentrations of these minerals.

The pH of a cat’s urine also plays a role. More alkaline urine tends to promote struvite crystal formation, while acidic urine encourages calcium oxalate crystals. Underlying medical conditions like kidney disease can alter urine pH and create an environment favorable to crystals (

Diet is another major factor. Dry, mineral-rich diets can promote crystal formation by concentrating minerals in the urine. Diets too high in magnesium, phosphorus, and protein may also contribute. In contrast, wet, high moisture diets can help dilute the urine and reduce crystal formation (

The Role of Tap Water

Tap water contains varying amounts of minerals like calcium and magnesium which can contribute to the formation of crystals in cats. The composition and quality of tap water depends on the water source and treatment methods used in that municipality.

Municipal tap water in the U.S. often contains added fluoride and other minerals like calcium and magnesium. While fluoride is added for dental health reasons in humans, excessive fluoride has been linked to increased risk of crystals in cats according to some veterinary studies (

Hard tap water with high mineral content provides a breeding ground for crystal formation when combined with a cat’s urine. The minerals crystallize and can lead to painful blockages. Studies have shown geographic regions with hard tap water tend to have higher rates of urinary crystals in cats (

Risks of Tap Water

Tap water can potentially pose some risks for cats prone to developing crystals and stones. One of the main concerns is that tap water often contains higher levels of minerals like calcium and magnesium. According to one study by Trupanion, areas with harder tap water were linked to higher rates of FLUTD (feline lower urinary tract disease) [1]. The minerals in hard tap water can concentrate in a cat’s urine, leading to crystal and stone formation.

Studies have found that cats drinking hard tap water have a more alkaline urine pH, which promotes the development of struvite and calcium oxalate stones [2]. These mineral-rich stones irritate the bladder and urethra, causing discomfort, urinary blockages, and even UTIs in some cases. So tap water containing excess minerals may facilitate an environment in the urinary tract where crystals and stones are more likely to occur.

Additionally, the fluoride and chlorine added to tap water can be problematic for some cats prone to urinary tract issues. Both have been linked to inflammation in the bladder and urethra. So tap water does appear to pose some potential risks when it comes to cats developing crystals or stones.

Alternatives to Tap Water

There are several alternatives to tap water that may help reduce the risk of crystals forming in cats:

  • Filtered water – Using a water filter, either a pitcher filter or a faucet mount filter, can remove contaminants from tap water that may contribute to crystal formation. Look for a filter certified to remove heavy metals, chemicals, and other impurities (Distilled Water for Kidney).

  • Bottled water – While more expensive than tap water, bottled waters such as spring water or purified water have gone through filtration processes to reduce impurities. Select a bottled water low in mineral content (Should I give my cat bottled water?).

  • Distilled water – The distillation process removes most minerals, salts, and other compounds that can lead to crystal formation. Distilled water may help cats prone to crystals dissolve existing ones and prevent new ones (Kidneys 5).

Talk to your veterinarian about the best water options for your cat based on their health history and risk factors for crystals.

Preventing Crystal Formation

The most important way to prevent your cat from developing crystals is to encourage increased hydration. Cats that don’t drink enough water are at higher risk for crystallization. Make sure fresh, clean water is always available and consider getting a cat water fountain if your cat isn’t drinking from a regular bowl. Cats tend to prefer flowing water. You can also add more moisture to your cat’s diet by feeding wet food. Dehydration concentrates the minerals in urine allowing crystals to form more readily.

Your vet may also recommend a special prescription diet formulated to promote the dilution of urine and alter the pH to prevent crystals. These prescription diets are designed to produce urine that doesn’t allow crystals to form and aggregate. Talk to your vet to see if a prescription urinary or kidney diet may be appropriate for your cat. These diets can be effective at preventing recurrence of crystals.

In addition to increased hydration and prescription diets, your vet may also recommend medications or supplements that help alkalinize the urine or prevent crystal formation. Your vet will be able to determine the right prevention plan for your specific cat based on the type of crystals identified.

Treating Existing Crystals

If your cat already has struvite crystals or bladder stones, the vet will likely recommend treatment to break them down and allow them to be passed out of the body. Common treatments include:

Surgery – For large stones that cause an obstruction, surgery may be needed to remove them. This is done under anesthesia and involves making an incision in the bladder to take the stones out.

Medications – Vets may prescribe medications like antibiotics to treat an underlying UTI contributing to crystal formation. There are also medications to help relax the urethra and promote urination, easing stone passage.

Diet – Special veterinary diets aim to dissolve struvite stones by creating urine that is undersaturated with stone-forming minerals. Feeding only this food and limiting treats helps maximize its effectiveness.

In many cases, a combination approach works best to eliminate existing crystals and prevent recurrence. Regular vet monitoring helps ensure treatments are working as intended.

When to See a Vet

If your cat is exhibiting any signs of trouble urinating, it’s important to get veterinary attention right away. Some signs that indicate an urgent issue include:

  • Straining or crying out while trying to urinate
  • Frequent trips to the litter box with little urine production
  • Blood in the urine
  • Excessive licking of the genital area
  • Irritability or restlessness

A complete obstruction of the urethra is an emergency situation and can quickly become fatal if left untreated. Males cats are especially prone to obstructions since their urethra is narrower. Symptoms of a blockage include:

  • No urine production at all
  • Vomiting
  • Lethargy
  • Loss of appetite
  • Dehydration

If you observe any of these urgent symptoms, don’t hesitate to bring your cat to the veterinarian or emergency animal hospital right away. Timely treatment is critical to prevent lasting damage or even death. At the first signs of trouble, it’s always better to err on the side of caution when it comes to your cat’s health.


In summary, while tap water is not directly linked to causing crystals in cats, it can contribute to their development. The minerals and contaminants found in tap water may lead to highly concentrated urine, increasing the chances of crystals forming. To reduce this risk, use filtered or bottled water for your cat’s hydration instead of tap. Also ensure your cat’s diet is designed to promote urinary tract health. If crystals do develop, quickly get veterinary treatment as they can be very painful and lead to dangerous blockages. With proper prevention and care, it’s possible to avoid troublesome crystals in cats caused by tap water. The key is monitoring your cat’s urinary health and making smart decisions about their water source.

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