A huge discussion, which caravanners can be quite emphatic about, is whether or not you should tow a caravan with full water tanks or leave them empty.
There’s no doubt about it, towing a caravan with full water tanks gives you better stability, eliminates water slosh and keeps you well prepared. However, towing with empty water tanks can give you better fuel economy and allow you more payload for other items.
So, which is better?
A few additional factors are at play when deciding whether you should tow with full or empty water tanks.
- How far away is your next destination?
- Are you able to fill up your water tanks when you get there?
- Are you going to be travelling in windy conditions?
- Are you trying to save money on the fuel budget?
- Do you have enough payload to travel with full water tanks?
There are solid arguments for both sides of the fence, so let’s have a look at the pros and cons of each scenario – towing with full water tanks and towing with empty water tanks.
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Towing with FULL Water Tanks
Full Water Tanks Can Help with Load Distribution
Technically, all caravans should be built to tow safely, irrespective of whether the water tanks are full or not. But, there are many factors that can greatly affect the handling, such as how the caravan has been loaded and if it’s being towed with a correctly set up vehicle.
Most caravan water tanks are positioned over the axle group or just in front of the axle.
The greatest portion of the weight should be over the axles, with some weight at the front and a little less at the back. With that in mind, filling up the water tanks will put the majority of your weight over the axles, which is perfect.
Working out the weight of your water is very simple:
1 litre = 1 kilogram
Have a look at the picture below for a quick visual on how to load a caravan correctly.
Regardless of whether you’re towing a caravan with full water tanks, you still need to make sure your load is evenly distributed for those times when you do travel with them empty.
Below is a great little video showing just how easily you can swerve out of control simply by having the weight unevenly distributed throughout the caravan.
▶️ VIDEO: Caravan Weight Distribution Explained
Full Water Tanks Provide Extra Stability
Filling up your water tanks for towing puts a lot of extra weight down low in your caravan. This effectively lowers the centre of gravity, which increases the caravan’s stability.
If you can imagine a car driving along with the roof fully loaded, but nothing packed inside of the car – the centre of gravity is up high, making the whole vehicle less stable and more likely to roll or crash in the case of an accident. You want that extra weight as close to the ground as you can.
When travelling on a windy day, you’ll be much more aware of how stable (or unstable) your load feels, especially when a crosswind hits your set-up. Crosswinds can be particularly common down the East Coast of Australia and in the Outback regions where the land is open and flat.
Full Water Tanks Can Increase Tow Ball Weight
Tow Ball Download Weight or Tow Ball Loading is the maximum weight that can be put onto the tow ball without lifting the tow vehicle’s front wheels – affecting it’s ability to steer and brake.
The acceptable tow ball weight in Australia recommends that about 10% (give or take a little) of the caravan’s fully-loaded weight should be on the tow ball. Filling your water tanks can increase that tow ball weight, which is why it’s so important to know your weights with and without water.
If your caravan weighs 3,000 kg
3,000 ➗ 10 = 300
Therefore, your Tow Ball Weight should be around 300 kg.
A properly loaded and well set-up car and caravan should remain stable on flat roads, as well as corrugations.
When you’re driving along a bumpy surface, the weight of the van comes off the ball and makes the van ‘tail heavy’ for a brief moment. It’s at that moment that a heavy side wind or bow wave of air from a large overtaking vehicle, can throw your stability off balance and cause the van to sway.
The reason why the tow ball weight recommendations are different across Australia, Europe and the USA all comes down to general road speeds. A higher tow ball weight is necessary when travelling at higher speeds, to reduce the risk of ‘sway.’
How to work out your Tow Ball Weight
There are three common methods people use to work out their caravan tow ball weight:
- With Ball Weight Scales
- Using Household Scales
- or at a Public Weighbride
Have a read of the full article below, which will take you through the step-by-step processes.
Hands down, the easiest way to find out the exact ball weight of your caravan is to grab yourself a set of Ball Weight Scales.
You’ll be able to see exactly what your ball weight is when the caravan is fully loaded. Then you can check to see the difference when the water tanks are full versus empty.
You may find that you need to distribute your load a bit differently to get the correct tow ball weight for your set up.
Don’t forget about the Grey Water Tank
Consider where your Grey Water Tank is positioned. They are generally installed wherever there’s spare room under the van, which can often be under the rear. If you’ve got waste in the Grey Water Tank, then travelling with full water tanks may be necessary to help evenly distribute the weight and get some more weight over the tow ball.
Full Water Tanks Eliminate Water Slosh & Caravan Sway
Towing a caravan with half-full water tanks creates ‘water slosh’ and instability, causing your van to sway with the water movement.
As you’re travelling along, any leftover water in your tanks is going to swish backwards and forwards and side-to-side with every movement. Think about the amount of momentum that waves of water can pick up as you brake, turn a corner or hit a bump in the road.
Say you’ve still got 40 Litres of water (or 40 fluid kilograms) swooshing your caravan around. Handling a big trailer at speed, with winds, potholes and overtaking trucks is enough to handle at the best of times. Don’t add any extra, unnecessary complications to the situation.
Other factors that can influence trailer sway:
- Driver skill
- Vehicle weight
- Caravan weight
- Caravan load distribution & centre of gravity
- Number of trailer axles
- Air turbulence
- Weather conditions
- Road conditions
- Condition of wheel bearings and brakes
- Suspension set-up for tow vehicle and trailer
- Tow ball and coupling clearances
Full Water Tanks Keep You Prepared
Towing a caravan with full water tanks keeps you well prepared. It saves you from having to search around for water during your journey before hitting the next camp.
Another benefit of travelling with water onboard is the ability to pull up camp anywhere, knowing that you’ve got all of your supplies on hand.
There is also the unfortunate possibility of the car breaking down along the way before you were able to fill up your water tanks. What if you find yourself stuck on the side of the road in the middle of no man’s land without water? Not only is that situation less than ideal, it could even become life threatening if help isn’t within reach.
If you know you’re just heading straight to another caravan park where water will be available, you may want to reconsider if you really need to be carrying all of the extra water weight unnecessarily. But… once you get into more regional and Outback areas where phone reception is as scarce as the water, I wouldn’t travel without it.
Practical reasons to have water onboard:
- Can camp anywhere
- Plenty of water in case of emergency or break down
- Ensures you’ve got good quality water
- No need to rely on the next town or camp having water available
- Can pull over to use the caravan kitchen, toilet and tap while travelling
Full Water Tanks Ensure High Water Quality
The last point I’d like to make about travelling with full water tanks is with regard to water quality.
It’s fair to say that much of the potable water around Australia is of a high enough standard for human consumption. However, some people are more sensitive to mixing up their water sources than others.
If you know that you may end up with an upset stomach if the water quality isn’t the same as what you’re used to, you may prefer to travel with full water tanks. Filling them up with your local town water or from your own fresh water tank can give you peace of mind that you’ve got good quality drinking water on board.
If you’ve ever had to deal with water tanks not filling up properly, here are some water tank filling tips to try.
Towing with EMPTY Water Tanks
Empty Water Tanks Can Result in Better Fuel Economy
It seems logical that the more weight your vehicle is pulling, the quicker you’re going to go through the fuel. However, this seems to vary so much between vehicles. We didn’t see a huge fuel difference in the Patrol while towing the 23 ft Jayco Starcraft, between full and empty water tanks. For us, the benefit of always having water on hand far outweighed the minor additional fuel usage.
Having said that, when you’re on a budget and trying to stretch those travel days even further, every dollar really does count.
Each vehicle is different, so you’d have to do the test yourself with your own car to see what the fuel difference is when towing with full water tanks, versus towing with empty tanks.
Empty Water Tanks Reduce Wear & Tear
Towing a caravan with empty water tanks can reduce the wear and tear on your vehicle and van. Simply put, the more weight that your car is pulling, the harder it has to work.
Without a doubt, extra weight means that there will be extra pressure on your gear box and motor. You may find that you need to service the vehicle more often as a result.
Remember that using a vehicle at or above it’s towing capacity is going to naturally cause more wear and tear.
Carrying around that extra few hundred kilos in water will also add to the wear and tear of your caravan suspension. It won’t damage it in any way, after all the van is designed to have full water tanks, but you may find the life of the suspension is shortened if the water tanks are constantly full.
Empty Water Tanks Allow More Payload for Other Items
When it comes down to it, you’ve only got a certain amount of payload (load capacity) available for your caravan. That payload needs to cover everything from food, linen, clothing, generator, additional solar power, cooking items, water and everything else that you’ll need for your trip.
Remember, 1 Litre of water = 1 kilogram
Let’s say you’ve got 400 kg of payload weight available and you fill up your two 90 Litre water tanks. Straight away, you’ve already used up 180 kg of payload, leaving just 220 kg for everything else.
Working out your payload:
- Pack your caravan with everything you’ll need for your trip
- Fill up your water tanks
- Hitch up your caravan and take it to a Public Weighbridge
- Unhitch your caravan on the weighbridge scales
- Record the current caravan weight
- Hitch the caravan back up and head home
- Minus the current caravan weight from your ATM (ATM – current caravan weight = available payload)
The ATM is the maximum weight that your caravan is allowed to weigh (you’ll find it on your caravan’s VIN plate).
If your caravan weight at the weighbridge exceeded your ATM, then you won’t be able to travel with full water tanks.
If the caravan weight came under your ATM, then give yourselves a high five – you are fully loaded with belongings and water and still came in underweight. You can travel with full water tanks.
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Always carry drinking water in the car
It’s important to make sure you’ve always got enough drinking water for everyone in the car in case of emergency.
A 10 – 20L container is good to always carry. If you’re not travelling around with full caravan water tanks, making sure you’ve got a jerry can of fresh water is even more important.
Empty Water Tanks Work Better if they Aren’t Located Over the Axles
Water tanks in caravans should be located as close as possible to the axle group (and evenly apportioned). Most modern caravan manufacturers are well aware of this and make it a standard part of their design.
However, sometimes the position of the water tanks can favour more to the front or rear of the van, creating a yo-yo effect from the unevenly distributed weight of the water. In this case, you’d be better off travelling with empty tanks, so as not to throw off the balance of the caravan.
Is it Better to Tow with Full or Empty Water Tanks?
Making the decision on whether you’re better off towing a caravan with full water tanks or keeping them empty really depends on your set-up and personal situation.
If you’re aiming to save money on fuel or need as much payload weight as you can get, then travelling with empty tanks will suit you better.
However, if you’re looking to increase stability, get a bit more weight over the tow ball and be fully prepared, go for full tanks.
|Towing with FULL Water Tanks
|Towing with EMPTY Water Tanks
|• Provides a lower centre of gravity
• Increases caravan’s stability
• Ensures most of the weight is over the axles
• Can help with load distribution
• Can help with tow ball weight
• Eliminates water ‘slosh’
• Always have water on hand
|• Better fuel economy
• Less wear & tear on the vehicle, caravan and suspension
• Eliminates water ‘slosh’
• Frees up payload for other items
What if Your Caravan Feels Unstable Whether the Tanks are Full or Empty?
At the end of the day, a well-designed caravan should feel stable and tow well, regardless of whether or not the water tanks are full. If your caravan feels unstable either way, there could be other factors at play. The most common causes of caravan instability is an incorrectly distributed load or incorrectly set up tow vehicle.
Some things that can cause caravan instability:
- Incorrectly distributed load
- Incorrect tow vehicle height or suspension
- Manufacturer fault
If you’re worried about the stability of your caravan, go and have a chat with your caravan manufacturer.
Full or Empty Water Tanks for Caravan Storage?
Now that we’ve covered towing with full or empty water tanks, let’s take a look at if you should leave water in your caravan tanks while it’s being stored.
A common myth says that leaving water in your tanks promotes algal growth, while others claim the opposite.
After doing the research for both sides of the fence, I’ve found that it really depends on how often you leave water sitting in your tanks and what your climate is like.
Take a look at the full article to see what’s going to be right for you.