Your caravan’s water tanks are the difference between a comfortable week off-grid and a dash to the nearest servo for bottled water. Most vans carry between 80 and 200 litres of fresh water across one or two tanks, and how you fill, drain and clean those tanks directly affects the quality of what comes out of your taps. Get lazy about it and you’ll end up drinking water that tastes like the inside of a plastic drum, or worse, water that makes you sick.
This guide covers the full cycle: filling safely on the road, draining properly before travel or storage, and sanitising your tanks on a schedule that keeps the water safe to drink. It applies whether you’ve got a single 95 litre tank under a pop-top or twin 120 litre tanks on a full off-road rig.
Filling Your Water Tanks
Filling looks simple: find a tap, connect a hose, wait. The problems come from where you fill and what you fill through. Not all water on the road is drinkable, and not every hose is safe for potable water.
Find the fill point and know your tanks
Most caravans have a dedicated fresh water inlet on the side of the van, usually a screw cap or a flip-up cover marked “water”. Some older vans fill through a deck filler on top of the tank instead. If you’ve got twin tanks, you may have separate inlets or a valve that lets you direct water to one tank at a time. Know which is which before you’re standing at a tap in the dark.
Use a food-grade drinking water hose
Never fill with a standard garden hose. Regular hoses leach chemicals and grow bacteria inside, and they’ll give your water a distinct rubbery taste. Buy a proper white or blue food-grade drinking water hose. They’re cheap and they last for years.
~$45
Where to fill safely
Good sources include caravan parks, town water taps marked as potable, and most rest areas with a tap connected to town supply. Be cautious with bore water, tank water at free camps, and any tap marked “not for drinking” or “non-potable”. If in doubt, run it through a filter and treat it, or don’t drink it.
Fit an inline water filter between the tap and your fill hose. A basic sediment and carbon filter removes rust, sand and most of the taste from questionable town supplies. Replace the cartridge every 3 to 6 months depending on use.
Don’t overfill and mind your weight
Water weighs a kilo per litre. A full 150 litre tank adds 150kg to your rig. If you’re heading somewhere with reliable water, there’s no point towing a full tank up a mountain range. Fill enough for the leg ahead, not the whole trip. Keep an eye on your payload, because water is one of the easiest ways to blow past your ATM.
Draining Your Water Tanks
You’ll drain your tanks for a few reasons: before a long tow to save weight, before storing the van, before sanitising, or to flush out water that’s gone stale or picked up an off taste.
Find the drain points
Each tank has a drain, usually a valve or a screw plug at the lowest point underneath the van. Fresh water tanks are separate from your grey water tank, so make sure you’re opening the right one. Some vans run the drain through a tap inside a hatch; others you’ll reach from underneath.
The draining process
- Park on level ground, or angle the van slightly towards the drain point so water runs out fully.
- Open the drain valve or remove the plug.
- Open a tap inside the van (turn the pump off first) to break the vacuum and let the tank empty faster.
- Let it drain completely. On twin tanks, do one at a time so you know each is fully empty.
- Close the drain and check for drips before you drive off.
Never drain your fresh water tanks in a national park, at a free camp, or anywhere sensitive. It’s a large volume of water and it can create bog holes and damage sites. Drain at a caravan park or a dump point where the ground can handle it.
Draining before storage
If the van’s going to sit for more than a couple of weeks, drain the tanks completely and leave the drains open or a tap cracked so the tank can breathe. Standing water in a warm tank is where bacteria and biofilm thrive. Empty tanks stay clean; full stagnant tanks turn into a science experiment.
Sanitising Your Water Tanks
Sanitising is the job most people skip, and it’s the one that matters most for your health. Over time, tanks build up biofilm: a slimy bacterial layer on the inside walls. It causes the musty taste and smell, and it can make you crook. A proper sanitise clears it out.
What you’ll need
- Plain unscented household bleach (sodium hypochlorite, around 4 percent)
- A clean bucket for measuring and mixing
- Your food-grade fill hose
- A full tank of fresh water to flush afterwards
The sanitising process
- Empty the tanks. Drain everything first following the steps above.
- Work out the dose. Use roughly 60ml of household bleach per 100 litres of tank capacity. For a 150 litre tank, that’s about 90ml.
- Mix and add. Dilute the measured bleach in a few litres of water in your bucket, then pour it into the empty tank through the fill point. Never tip neat bleach straight in.
- Fill the tank completely with fresh water. Filling on top of the bleach mixes it through.
- Run the taps. Turn the pump on and open every tap, including the hot water and any outside showers, until you smell chlorine at each one. This gets the solution through the whole plumbing system, not just the tank.
- Let it sit. Leave the chlorinated water in the tank and lines for at least 4 hours, ideally overnight.
- Drain it all out. Empty the tank completely at a dump point.
- Flush twice. Refill with fresh water, run all the taps until the chlorine smell is gone, then drain again. Repeat if you can still smell bleach.
If you’d rather not handle bleach, food-grade sanitising products like Aquis or Puriclean do the same job with clearer instructions and less smell. They cost more per treatment but they’re easier to get the dose right.
Don’t forget the hot water system
Your hot water tank holds water too, and it’s often the worst offender for smell because the warmth accelerates bacterial growth. Make sure you run the hot taps during the sanitise so the chlorinated water reaches the hot water unit. Some travellers periodically drain and flush the hot water tank separately as well.
How Often To Do Each Job
| Job | How Often | When |
|---|---|---|
| Fill | As needed | Before each leg, from a trusted source |
| Drain (partial) | Every few weeks | To refresh water that’s gone stale |
| Drain (full) | Before storage / long tows | Whenever the van sits or weight matters |
| Sanitise | Every 3 to 6 months | Start of a trip, after storage, or if water tastes off |
On a Big Lap you’re using and refilling your tanks constantly, so water rarely sits long enough to go bad. Sanitise at the start of your trip, then again roughly every three months. If the van has been parked up over a wet season or between trips, always sanitise before you drink from it again.
Gear That Makes It Easier
A few cheap bits of kit turn tank management from a chore into a two-minute job.
Keep your drinking water hose in a sealed bag separate from any hose you use for washing down or grey water. Cross-contamination is one of the easiest ways to undo all your good work.
- Always fill through a dedicated food-grade drinking water hose, from a trusted potable source, and consider an inline filter.
- Don’t tow a full tank when you don’t need to. Water is 1kg per litre and eats into your payload.
- Drain fully before storage and leave a tap cracked so the tank can breathe.
- Sanitise with unscented bleach (about 60ml per 100 litres) every 3 to 6 months, run it through every tap including the hot water, then flush thoroughly.
- Never drain fresh tanks at free camps or in national parks. Use a dump point.
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