Nobody writes about water. It’s free, it comes out of a tap, and there’s a bowl in the kitchen that gets topped up when somebody notices.
Which is a shame, because hydration underpins more of a dog’s digestion than any supplement does. Constipation, hard stools, poor appetite, sluggish digestion and a fair number of urinary problems all trace back to a dog who simply isn’t drinking enough — and it’s one of the few things you can fix this afternoon at no cost.
How much a dog actually needs
The usual figure is around 50 to 60ml per kilogram of body weight per day, so roughly 40 to 50ml per pound. A 20kg dog needs somewhere in the region of a litre a day.
That’s total intake, not what comes out of the bowl. Wet food is around 75 to 80 per cent water, so a dog on tinned food gets a substantial proportion of his requirement from his dinner. A dog on dry kibble, which is around 8 to 10 per cent moisture, has to drink almost all of it.
Which is why the same dog switched from wet to dry appears to start drinking enormously. He hasn’t developed a problem. He’s making up the difference.
Requirements go up with heat, exercise, lactation, and several illnesses. They go up in winter too, more than people expect, because central heating is drying.
Steady hydration also matters for the population doing the work further down. Fermentable fibre needs water to function, bulking fibre without fluid causes exactly the problem it’s meant to solve, and a dog on Probiotics for Dogs with a properly hydrated gut gets more out of them than one running slightly dry — it’s unglamorous, and it’s the foundation the rest sits on.
Why dogs under-drink
Thirst drive is less sensitive than you’d hope, and it declines with age. An older dog is often mildly dehydrated as a baseline state.
Bowls in inconvenient places. Dogs are lazy about it. A bowl in the utility room gets used less than one in the room the dog actually lies in.
Bowl design. Deep narrow bowls press on whiskers, which some dogs dislike intensely. Dogs with sore necks or backs struggle to lower their heads far.
Slippery floors. A dog who has slipped once at the water bowl will hesitate afterwards. This one is genuinely common and completely invisible unless you think of it.
Stale water. Dogs are more particular than they get credit for. Water sitting all day in a warm kitchen tastes of the bowl.
Bowl hygiene. A rinsed bowl develops a biofilm — a slimy bacterial layer that survives a quick swill. Dogs notice.
Metal taste. Some dogs dislike stainless steel, some dislike plastic. It’s worth trying ceramic if a dog seems reluctant.
Being unwell. Nausea suppresses drinking, which is exactly when they need it most.
Getting more in
The reliable methods don’t involve hoping.
Add water to the food. The single most effective change. Warm water into kibble, left to stand ten minutes, roughly the volume of the food itself. Most dogs prefer it and you’ve added a couple of hundred millilitres without a fight.
Switch some or all of the diet to wet. Even replacing a third of the ration makes a measurable difference.
More bowls, in more rooms. Including one wherever he actually sleeps.
Wider, shallower bowls, off slippery floors, on a mat.
Fresh water twice a day, not topped up. Empty, rinse properly, refill.
Wash bowls daily with hot water and detergent. Ceramic or stainless steel rather than scratched plastic.
Flavour it very slightly if he’s reluctant — a spoonful of unsalted bone broth, or the water from boiling plain chicken, in one of several bowls.
Ice cubes, which plenty of dogs treat as a toy and consume a surprising amount of water through. Perfectly safe, despite a persistent internet myth linking them to bloat.
A pet water fountain, which suits some dogs enormously and does nothing for others. Worth trying if you’ve a fussy drinker.
Take water on walks. A collapsible bowl and a bottle, particularly in summer and for anything over half an hour.
Checking whether he’s dehydrated
Two quick tests worth knowing.
Skin tent. Lift the loose skin over the shoulders and let go. It should spring back immediately. A slow return suggests dehydration; a peak that stays is significant.
Gum check. Gums should be moist rather than tacky. Press a finger against one — the pale spot should refill with colour in under two seconds.
Also: sunken-looking eyes, thick stringy saliva, lethargy, and skin that’s lost its usual elasticity.
Note that the skin tent is less reliable in very thin dogs and in older ones, where skin elasticity is reduced anyway. It’s a guide rather than a verdict.
What happens when he’s short
Harder stools and constipation. The colon’s job includes reclaiming water. A dehydrated dog reclaims more, and the stool arrives drier.
Slower digestion generally.
Reduced appetite.
Concentrated urine, which increases the risk of urinary crystals and stones, and makes bladder infections more likely.
Reduced exercise tolerance and worse heat regulation.
Kidney strain, particularly in older dogs and those with early kidney disease, where hydration is one of the main things you can influence.
Too much is a warning sign
The mirror image, and considerably more urgent.
A dog who suddenly starts drinking noticeably more than usual — emptying bowls, seeking water out, asking to go out more, or having accidents overnight — needs a vet appointment rather than a bigger bowl.
Increased thirst is an early sign of several serious and treatable conditions: kidney disease, diabetes, Cushing’s, liver disease, uterine infection in unspayed bitches, and some cancers.
If you can, measure it before the appointment. Put out a known volume in the morning, top up from a measured jug, and record the total over 24 hours. Sustained intake above roughly 100ml per kilogram per day is generally considered excessive. That number is genuinely useful to a vet and takes a day to collect.
Water sources to avoid
Standing water, puddles and stagnant ponds. The main route for giardia, and a common cause of stubbornly soft stools.
Blue-green algae, on lakes and ponds in warm weather. Rapidly fatal and there is no antidote. If the water looks like pea soup or has scum on it, keep him out and don’t let him drink.
Sea water. Small amounts are unavoidable and salt poisoning from a dog repeatedly retrieving from the sea is a real thing. Take fresh water to the beach and offer it often.
Puddles on roads and car parks, for antifreeze and oil runoff.
Toilet bowls, mainly for the cleaning products.
Water butts and stagnant garden containers.
Travel, boarding and different water
Worth planning for, because a change of water supply causes more upsets than people credit.
Different areas have genuinely different water — hardness, mineral content, chlorination. A dog who moves from a soft-water area to a hard-water one, or drinks bottled water on holiday when he’s used to tap, can get loose stools from that alone.
If you’re going away for a week, take a few litres from home and mix it with local water in decreasing proportions across the first few days. It sounds fussy and it prevents a genuinely common problem.
For boarding, mention it if your dog is at all sensitive, and check they’ll be using fresh water rather than a communal bowl topped up occasionally.
Around exercise and heat
Don’t let him empty a full bowl straight after hard exercise. A dog who does that frequently brings most of it back up. Offer smaller amounts more often, and let him cool down for a few minutes first.
In warm weather, water everywhere, shade, and walks early or late rather than in the middle of the day. Flat-faced breeds, thick-coated breeds, overweight dogs and older dogs are all considerably less able to cope with heat than they look.
Watch for the early signs of overheating — heavy panting that doesn’t settle, bright red gums, drooling, unsteadiness. Cool water, shade, wet towels over the body, and a vet, because heatstroke kills quickly and dogs deteriorate after they appear to have recovered.
Multi-dog households
Two practical problems that are easy to miss.
Bowl competition. A lower-ranking or more timid dog will often wait rather than drink alongside a pushier one, and if there’s only one bowl he may end up drinking considerably less than he needs. The fix is more bowls in more rooms, so nobody has to negotiate for water.
Contamination and hygiene. A shared bowl gets slimier faster and is a route for passing things around — giardia in particular. If one dog is unwell, separate the bowls entirely until it’s resolved.
Also worth watching: a dog who suddenly starts guarding the water bowl. It’s unusual, it’s a sign of anxiety or discomfort rather than dominance, and it means somebody isn’t drinking.
Puppies, and older dogs
Puppies dehydrate far faster than adults because they have almost no reserves. A puppy with diarrhoea or vomiting can be in trouble within hours rather than days, and refusing water in a puppy is a same-day call. They also need water constantly available during house-training rather than restricted overnight, which is advice that still circulates and is genuinely unhelpful — restrict the water and you get a dehydrated puppy who still has accidents.
Older dogs are the group most likely to be quietly under-drinking. Reduced thirst drive, arthritis making it awkward to lower the head, less inclination to walk to another room, and often early kidney changes that increase requirement at exactly the point intake falls.
For a senior dog, the single most useful change is getting water in through food rather than relying on the bowl. Wet food, or water added to kibble, every meal. It’s the difference between a dog who is adequately hydrated and one who is chronically slightly short, and the second describes a great many older dogs.
The one habit worth adopting
Once a week, actually look at the water.
Is the bowl clean, or does it feel slightly slimy? Is the water fresh or has it been there since yesterday? Is the bowl somewhere he’d naturally go? Is it on a slippery floor?
Then, when you next fill it, note roughly how much and how quickly it goes. You’re building a sense of what normal looks like for your dog — which is the only way you’ll notice when it changes, and a change in drinking is one of the most useful early warnings you’ll ever get.