The human body is 55-78% water and a moderate hike loses you 1-1.5 litres an hour. Over a 20km day, that's 4-6 litres lost — and dehydration in Aussie summer heat is a genuine killer. The trick to staying hydrated isn't carrying more water — it's drinking it CONSISTENTLY, every 15-20 minutes. And the only way that habit survives a long hike is if water is genuinely accessible.

That's why hydration packs (the bladders that sit in your backpack with a drinking tube over your shoulder) have largely replaced traditional water bottles for serious hikers. Here's the practical buyer's guide.

Photo by Serhii Danevych on Unsplash

Hydration packs are typically small and light — meaning the bladder inside is the more important component. Most bladders are interchangeable between brands, so you can buy your favourite pack and your preferred bladder separately.

Brands worth knowing: Camelbak (the original, still very good), Osprey, Source, HydraPak, Platypus. The Aussie brand Sea to Summit also makes excellent reusable squeeze-bottles for shorter trips.

The biggest problem with hydration bladders is mould. They live in the dark, often damp, often warm — perfect mould conditions. The more accessible the inside, the easier to clean.

Two opening designs:

• Screw-cap top — easier to fill (especially under a tap or in cold weather with gloves), harder to clean. Look for the larger-cap versions for better cleaning access
• Slide-top opening — the entire end of the bladder opens, allowing you to wipe inside and drip-dry. Easier to clean. Slightly fiddly to fill

Cleaning kit: a brush set specifically for bladders ($20-30) is a worthwhile investment. Use mild dish detergent + warm water, rinse thoroughly, hang to dry inverted. Never store wet — that's how mould starts.

For mould prevention: drop a denture-cleaning tablet into a full bladder once a month, leave overnight, rinse thoroughly. Most modern bladders have anti-microbial treatment but it's not a substitute for cleaning.

Photo: Norbert Buduczki / Unsplash

• 1L — running, mountain biking, half-day walks in cool weather
• 2L — sweet spot for day hikes, most active use
• 3L — full-day hikes in summer or remote country, longer rides
• 4L+ — hot-weather walking, no refill points

Australian summer rule: 4L per person per day if you can't refill. 6L+ for serious desert/Pilbara/Centre walking. Carrying water adds weight (1L = 1kg) but dehydration in 40°C+ is debilitating in hours.

For multi-day trips, plan refill points in advance — creeks, water tanks at huts, town stops. A water filter (Sawyer Mini or Katadyn BeFree) lets you refill from any natural source.

• Bite valve material — silicone lasts longer than rubber. Replaceable bite valves let you swap when worn
• On/off lever — prevents accidental squeeze (your pack pressing the tube in tight country) leaking water everywhere
• Dust cap — keeps dirt out of the bite valve when bushwhacking through scrub
• Insulated tubes — prevent water from heating up in summer or freezing in alpine winter
• Magnetic clips attach the tube to the shoulder strap so it's always where you reach for it

Photo: Drew Farwell / Unsplash

For dedicated hydration packs (vs adding a bladder to a hiking pack), look for:

• Separate bladder compartment — sealed so a bladder leak doesn't soak the rest of your gear
• Mesh ventilation panel against your back — water sweat is the worst
• Hip belt for stability on heavier loads — water moves around if not stabilised
• Quick-release bite valve port — you can pull the tube out easily for cleaning or refill
• Reflective trim if you're running or cycling at dawn/dusk

For multi-day hiking, just add a bladder to your existing hiking pack — most packs have a dedicated sleeve.

The biggest hydration mistake on the trail: waiting until you're thirsty. By that point you're already 1-2% dehydrated and performance has dropped 10-15%.

• Sip every 15-20 minutes whether thirsty or not
• Aim for 500ml-1L per hour in moderate conditions, more in heat
• For hard or hot days, add electrolytes (Hydralyte, Gatorade powder, salt tablets) — water alone isn't enough; you also lose sodium, potassium, magnesium
• Pee colour is the easy gauge: pale yellow = hydrated, dark = drink more

Camelbak's slogan: "Hydrate or die." Slightly dramatic, but the principle is right.

For Aussie day-hiking: 2L Camelbak (or equivalent) with a slide-top opening, insulated tube, on/off bite valve. Spend $80-130. Clean it after every trip. Add electrolytes for hot days.

For multi-day hikes, the same bladder slips into your hiking pack. The hydration habit is the easiest performance upgrade for any walker — once you've used a hydration pack on a hot summer hike, you don't go back to fishing a water bottle out every 20 minutes.