“Dog Rocks” & Meaningless Woofle

It’s a disappointment to find Pete Wedderburn, a qualified vet, endorsing “Dog Rocks”. Here’s what he printed in the Telegraph:

“The brown patches caused by dog urine on lawns are a perennial issue (to borrow a gardening term). Some people claim that a daily dollop of tomato ketchup in the dog’s dinner stops this but evidence is lacking. Dog Rocks are the most popular product marketed to help: these are placed in dogs’ water bowls, claiming to filter out excessive nitrogen and urea from the water. A high concentration of nitrates can cause grass to turn yellow or brown: the idea is that if less nitrates go into the dog, less come out the other end. Dog Rocks claim success in 80 per cent of cases when used according to instructions; they are widely available in pet shops and online (dogrocks.co.uk).”

It is amusing that Wedderburn dismisses ketchup as a solution for lawn burns on the basis of a lack of evidence and then recommends dog rocks instead, via an appeal to popularity. One might have thought that, given his science education, he would know that popularity isn’t evidence for efficacy. In his defence, he doesn’t explicitly claim that dog rocks work – he just says that the company does. Perhaps he simply assumed on good faith that a company claiming to have conducted laboratory tests on their product must be selling something legitimate – which is of course what we really ought to be able to assume, in an ideal world. Unfortunately, this world is not ideal.

According to the the company’s website, dog rocks are “an igneous Rock with absorbing & retaining qualities” that will “stop pet urine ruining your lawn, grass, shrubs and hedging”. The site offers no evidence to back up these claims, and is home to a plethora of archetypal pseudoscience – loose ideas arranged clumsily around science jargon like “stable matrix”, “micro porous medium”, “ion exchange” and “trace elements”. The marketers print the word “PROVEN” on their product packaging in big red capital letters and, as mentioned above, claim that their product is “laboratory tested”. But they fail to offer even the vaguest insight into the nature of these tests, providing no reference whatsoever to study design, who did the testing, or whether the research was published (or even written up), let alone quantitative information  like effect sizes, standard deviation, p-values, etc. Even anti-ageing face-cream companies manage to pay enough lip-service to transparency that we can go and see that their effects are based upon the subjective reports of 20 women brought into their own lab and not peer-reviewed.

Lack of peer-reviewed studies and misuse of science words are both pseudoscience red flags. Other red flags exhibited by the website are: a page of testimonials, repetitious appeals to nature (dog rocks are “100% natural!”), appeals to pH woo (dog rocks “do not change the pH balance of dog’s urine so they should not harm your dog at all”), and a sort of variation on the appeal to ancient wisdom – I’ll call it “provincial wisdom” (dog rocks were “discovered in Australia by an Aboriginal Gardener in the 1990s”).

A quick tour around the website confirms that discerning dog-owners most certainly are not this company’s target market, and makes it clear beyond any reasonable doubt that these “lab tests” are either irrelevant to the question of whether the product actually works, or simply non-existent. Here’s the “technical blurb” (that’s their term, by the way).

Dog Rocks are a coherent Rock with a mechanically stable framework meaning no significant mineral particles are released into the pet’s drinking water, in other words, Dog Rocks do not break down or leech anything into the pet’s drinking water. Dog Rocks form a stable matrix and a micro porous medium in which active components are able to act as a water-purifying agent through ion exchange. For this reason, when placed in water, Dog Rocks will help purify the water by removing some harmful trace elements giving your dog a cleaner source of water.

Perhaps it’s crude of me to even say this, but to my mind one of the most reliable indicators of junk science and B/S is simply the quality of writing. It doesn’t take a literary connoisseur to notice that the writing style exhibited on the Dog Rocks website is cringeworthily naff and unsophisticated, and it has what I would describe as an awkwardly ingratiating, cloying tone. Although that isn’t enough to dismiss scientific claims, in my experience, this particular form of prose is a strikingly accurate predictor of pseudoscience. Fortunately for our purposes, however, we have much more to sink our teeth into than that.

You might have noticed that no explanation is offered as to how the removal of “harmful trace elements” should result in a change in urine composition such that lawn burns would be prevented. Such ambiguous conflation of terms is yet another red flag: it’s not “harmful trace elements” that cause lawn burns, it’s urea and nitrates (both nitrogen-containing substances). This irrelevant appeal to TOXINS, TOXINS, EVERYWHERE and the promise to remove them seems to have been thrown in there opportunistically as a bonus selling point. You might also have noticed that ion-exchange is a two-way street, yet according to the distributors, nothing is released from the product into Buster’s water. Which is it, Dog Rocks?

I visited the FAQ section to find out more about how the product is supposed to work. Under the heading “How do DOG ROCKS work?”, the “technical blurb” quoted above is re-printed verbatim, except with a different incarnation of woofle following the phrase, “For this reason”:

For this reason, when placed in water, Dog Rocks will help purify the water by removing some nitrates, ammonia and harmful trace elements thereby giving your dog a cleaner source of water and lowering the amount of nitrates found in their diet thereby lowering the amount that is expelled in their urine. An overload of nitrates in urine will cause lawns to burn. Dogs do produce nitrates as a by-product from the protein in their diet, but the difference between too much nitrate that will kill the grass and the amount of nitrate that will be good for the grass is very small.

Carnivores have particularly high levels of nitrogen in their urine because their diets include so much protein, and the digestion of amino acids (the building blocks of protein) creates nitrogenous waste, primarily in the form of urea. As the above quote alludes to, diluted urine can be used as a fertiliser, precisely because it contains nitrogen – one of the most important macronutrients for plants. However, at high concentrations, it causes chemical burns to roots by sapping water from them as a result of osmotic pressure. Evidence that dog rocks can transform weedkiller-wee into fertilizer, as they claim, however, is entirely absent.

On the website, the manufacturers try to gloss over the fact that the nitrogen in dogs’ urine comes overwhelmingly from the protein that they eat with their assertion (featuring in the last quote) that “the difference between too much nitrate…and the amount…that will be good for the grass is very small”. The amount of urea in canine urine is 3.5 ± 2.4 mg/dl* – like human urine, it already varies quite considerably. The manufacturers are basically admitting that the reduction in nitrogen concentration achieved by dog rocks will be “very small”, but hanging on to the case for efficacy by saying that a very small reduction is all that is needed. Their use of the phrase “very small”, without any quantification or context is entirely unscientific and misleading. Small relative to what? An infinitesimal is “very small”; so is an electron; so is an ant; so is a Falabella pony, all relative to their contexts. 

The company fails to give a threshold concentration value of urinary nitrogen beyond which urine burns plant roots, and below which it doesn’t (which is fishy in and of itself – this would have been one of the most important things to determine in those “lab tests” they say they conducted). If the change in nitrogen concentration effected by dog rocks is “very small”, then the product should only work in the subset of cases in which a dog’s initial urinary nitrogen concentration happens to be just above this undeclared value, and for owners to notice a change would require that individual dogs always produced urine with that same concentration – just a “very small” fraction above the magic value  which they don’t. In reality, urea concentration fluctuates from pee to pee – the ability to vary urine concentration is one of the most important properties of the mammalian kidney. A “very small” change would would be drowned out by the noise of this daily variation. The only way I can see dog rocks working is if they were to effect a “very big” change which, given the relatively enormous amount of protein dogs eat, is physiologically implausible. So, assuming that dog rocks do actually remove nitrates from water (the website gives us no reason to believe that they do, and plenty of red flags to suggest that they probably don’t), the idea that this would translate into prevention of lawn burns in anywhere near 80% of cases is wholly unconvincing.

To summarise, the company has failed on four levels:

1) It provides no demonstration that the nitrates in the water a dog drinks contributes significantly towards its propensity to produce lawn spots.

2) It provides no evidence that dog rocks lower nitrate concentration in drinking water, nor does it describe a plausible mechanism for how they might do so, beyond unspecified “ion exchange”. (Incidentally, if these things really could absorb nitrates, wouldn’t the company be a major seller to people who own expensive aquarium set-ups?)

3) It provides no evidence, if indeed dietary nitrates consumed in water did play a significant role, that their product could significantly reduce nitrate content in dogs’ urine, relative to the nitrates coming from other sources (particularly the meat that they eat).

4) It provides no evidence that, if indeed their product did significantly reduce the nitrate content in dog urine relative to the nitrates coming from other sources, this would translate into an impact on lawn burn.

Any evidence filling in the logical gaps in their sales pitch represented by points 1-4 above would be helpful to Dog Rocks. A demonstration of each stage, along with a functional explanation, would be most convincing. However, demonstration of point 4 alone would be a good start in making their case for efficacy. They could conduct a randomised controlled study, submitted to peer-review, in which a group of, say, a hundred volunteers used dog rocks for a few months, and a hundred used “normal” rocks instead. The outcomes could be quantified by counting the number of lawn burns at the beginning and end of the trial, and then the results statistically analysed to determine whether any significant reduction had been achieved.

Something tells me that Dog Rocks won’t rise to the challenge.

I couldn’t help quoting what one Amazon reviewer of the product said in their concluding paragraph: “The ONLY truly effective solution to brown patches on your lawn is to pour a bucket of water on the exact spot that your dog has just had a wee, as soon as they have done it. If that’s not practical, then your next best solution is to save the money you would be spending on Dog Rocks every two months, and buy 2 rolls of turf. Cut out the dead patches on your lawn, and replace them with new turf. Repeat every two months. Job done.”

*I have been unable to ascertain whether this value of 3.5 +/- 2.4 mg/dl refers to deviation across different dogs, over an individual dogs’ different pees, or a combination of the two ranges. If any vets are reading and can shed light, this would be nice for completeness. 


10 thoughts on ““Dog Rocks” & Meaningless Woofle

  1. a lot of New Zealanders believe you can stop dogs pooing on your lawn by leaving plastic bottles half-filled with water lying around on your lawn. I kid you not.

  2. This is a very detailed, well written article that has answered a lot of the questions I have surrounding Dog Rocks. I too did not fall for the psuedoscience hokum printed on their website – it just doesn’t make sense.

    So basically, they are suggesting that Dog Rocks will remove small amounts of nitrates from the water but you actually need to feed your dog a low-protein diet to keep lawn burn to a minimum? And that’s pretty much all there is to it? I really hope this is the case….

    My dog has been staying with a relative and (unbeknown to me) has been drinking from a bowl containing these rocks and I’m really annoyed about it. I am just hoping that the Dog Rock company’s claims that amount to little more than ‘snake oil’ are as innocuous as ‘reducing nitrate levels’ in dogs drinking water and not something that is going to change the composition of dog’s urine and cause potential kidney or liver damage.

    I’m certainly no expert in this field and I know this may come across as paranoid but if substances that should be washed out of are not able to because Dog Rocks are interfering with biological processes, then this is a major cause for concern. If nitrates are such a problem in tap water, then surely merely watering your grass would kill it!?!

    There are absolutely no scientific studies available on this product and there does not appear to be any endorsements by veterinary bodies or vets themselves, which is rather unnerving. People are being taken in hook, line and sinker by clever wording and terrible science and in the process could be doing irreversible harm to their pets. All for the sake of keeping their grass green…….

  3. A simpler test of the (in)efficacy of Dog Rocks might be to collect urine (or an adequate substitute), measure nitrogen levels over two consecutive days, the add Dog Rocks to the urine on the third day, measuring levels daily over the length of the experiment (seven days, perhaps?). The second day would alert us to the possiblenatural, inevitable breakdown of nitrates over time, while the remaining days should indicate ifDog Rockshave any effect on nitrates.

    Less seriously, “rolls of turf” are called “sod” stateside (we haven’t the other, naughtier meaning here).

  4. Thankyou for your detailed article on the Dog Rock scam. You hit the nail on the head. Nitrogen and urea are indeed the culprits within the dogs urine that burn the lawn, but those nutrients come from dogs food, not the water.

    I live in Western Australia, and looked up the chemical analysis of the water that we get from the tap. The Water Corporation removes all the nitrogen, and nitrates from our drinking water, or else it would promote the growth of algae/ bacteria in the water, if the chlorine levels were depleted. How can dog rocks possibly remove from the water, what is not there in the first place?

    ( I am unsure of nitorgen and nitrate levels in farm dams etc …… )

    The Dog Rocks company has not considered the possibility of algae type growth on the rocks themselves. My brother insists on using these dog rocks, but will not reason with me regarding the science of how they can’t possibly work. If I remove the rocks from the dogs bowl, he gets very very angry, insisting that his precious lawn will suffer. So, every few days I need to boil these rocks in a pot of water to kill the bacteria that grows on and in the rocks. when you sniff the rocks, you can really smell that mouldy / bacteria type smell.

    So…… does it really purify the drinking water for the dogs??? I think not.


  5. Judging by the huge numbers of people singing the praises of Dog Rocks I’ve decided there are enough gullible dog owners, with more money than sense, for me to make my fortune.

    Homeopathic anti-patch spray. A small sachet of liquid (100% safe H2O) is added to 2l of water which is sprayed onto the freshly peed-on grass. Not only is it safer than DogRocks, but it actually works!

    Sachets are £10 for a pack of 50 and the special agitator/sprayer is £10.

  6. w00t! I got a reply from them, with some data! Here is my reply to their email….

    Thanks for the information on the method of action proposed for DogRocks. The Water Testing results were especially interesting, despite there being no reference to the source of the information, the methodologies used or who performed the analysis. However, I shall take your results on faith (mainly because I could believe you’d make them up).

    The email you sent was very long, so I’ll just extract some of the key details. There are two claims I would like to address. First…

    “By lowering the amount of nitrates found in their drinking water Dog Rocks are lowering the amount that is expelled in their urine. It is an overload of nitrates in urine that causes the brown patches on the grass.”

    In the table showing the Water Testing results the amounts of Nitrate do indeed drop, from 8.49 to 8.32 mg/L – a, not very impressive, 2% reduction. Being as the majority of nitrates in dog urine come from their food your product will, at best reduce nitrates by less than 1%. Such a reduction is not going to have any effect on the state of owner’s lawns in the overwhelmingly huge majority of cases.

    But it gets worse. What happened to the nitrate that disappeared. Either it got absorbed by the DogRocks or they transformed it to something else. And that’s where we come to the second point…

    “Dog Rocks do not break down or leech anything into the pet’s drinking water.”

    One thing that the Nitrate could have been converted to is Nitrite. And the data you supplied show that the amount of Nitrite in the water went up from undetectable (<0.001 mg/L – effectively zero) to 0.135 mg/L. So much for not leaching anything into the water. But, there's more. Nitrite is also responsible for turning lawns brown, so the tiny amount of Nitrate removed by DogRocks is almost exactly compensated by the extra Nitrite in the dog's water.

    And the last straw. Nitrate is quite a bit more harmful that Nitrate. The levels of Nitrite in the dog's water (0.135 mg/L) are higher than the permitted levels in a Water Treatment Works (source: Thames Water Drinking Water Standards – http://www.thameswater.co.uk/your-account/7486.htm).

  7. Ooops! Last paragraph should read…

    And the last straw. Nitrite is quite a bit more harmful that Nitrate. The levels of Nitrite in the dog’s water (0.135 mg/L) are higher than the permitted levels in a Water Treatment Works (source: Thames Water Drinking Water Standards

  8. I have found dog rocks to be highly effective in preventing brown patches appearing on my lawn. They key to their effective usage is in refining the aim of your throwing arm. Whenever the dog starts his sniffing routine on your lawn, aim the rock at his head. Since employing this technique, the brown patches have all but disappeared.

    As an additional benefit, I have become very popular in sharia law circles where similar techniques are employed to reduce adultery in women.

  9. I the company produces two things: cleverly marketed inert rocks, and glowing testimonials.

    My friend bought these. She’s got enough background that she should have known better. It was immediately obvious that they wouldn’t, and couldn’t have any effect.

    And they didn’t.

    (Maybe it’s like homeopathy. Before I knew anything about it, a girlfriend took me to see a homeopath. I was dutifully taking the sugar beads until I made some skeptical comment, and she said, “You have to believe in it or it doesn’t work!”

    At that point, I looked it up.


    So, maybe I similarly destroyed the efficacy of these magic rocks.

    Maybe you’re doing the same by publishing your essay.

    Better take it down now… think of all the people who are now getting spots on their lawns because of you!)

  10. Thank you for writing this. It seemed like pure BS to me, but here it is 2 years after these posts and still for sale and getting good reviews on Amazon… I dont get it but what I did get when I looked at their website was the feeling of being a sucker. So I will kep looking for a solution…

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