How big should your campervan water tank be in a HiAce?

Your campervan water tank can’t be planned separately from the toilet and waste system. A portable cassette alone can hold 21 litres of waste and 15 litres of flush water, according to Thetford Australia. Start with the trip, then check the weight.

How much water should a HiAce camper carry?

A 50-litre campervan water tank is a sensible starting point for two people spending four days away, provided you aren’t using it for showers. That capacity covers drinking water plus a modest allowance for cooking and washing.

Parks Victoria tells campers to carry four litres of drinking water per person each day. Two travellers staying four days therefore need 32 litres for drinking, leaving 18 litres in a 50-litre tank for cooking, washing dishes and a small reserve.

That figure isn’t enough for regular showers, and hot weather or remote travel calls for a larger safety margin. Work from your longest gap between reliable refills. Don’t size the tank around a weekend if the van will later spend a week away from serviced campsites.

Weight decides whether a larger tank is sensible. Toyota Australia’s August 2025 specifications list a 3,300kg gross vehicle mass and 2,240kg maximum kerb weight for the automatic LWB van. That produces about 1,060kg of nominal payload before the conversion, occupants and luggage consume it.

Take a converted van that weighs 3,090kg with both travellers, fuel, food and normal gear aboard. Against the 3,300kg Toyota GVM, it has 210kg spare before water. Filling the proposed 50-litre potable water supply adds about 50kg, lifting the van to roughly 3,140kg and leaving around 160kg for anything omitted from the weighbridge load.

Use that as a worked method, not a claim about every HiAce. Tanks, cabinetry, batteries and different HiAce variants change the result. Weigh your completed van in travelling condition, subtract that reading from its plated GVM, then check whether a full tank leaves enough capacity for passengers and gear.

Count the toilet supply separately. The Porta Potti 365 carries a 15-litre flush tank on top of your drinking and washing supply, according to Thetford Australia. A removable drinking-water container can also provide a reserve without making every trip carry the maximum fixed capacity.

Where should you empty grey water?

Store grey water until you reach a disposal point that confirms it accepts it. Grey water is used water from your sink, and fitting a tank doesn’t give you permission to release it onto a campsite, roadside or stormwater drain.

For the same four-day example, a 20-litre grey-water tank is a workable starting point if it collects sink water rather than shower water. In the heaviest case, full 50-litre fresh and 20-litre grey tanks add about 70kg to the 3,090kg payload example, taking the van to about 3,160kg and leaving roughly 140kg below its 3,300kg GVM.

Water transferred from the fresh tank into the grey tank doesn’t add new weight. The full-tank calculation still matters because you may refill the fresh supply before reaching a place that accepts grey water. Size both tanks for that temporary worst case, not only for normal use.

Check the rules for the campsite, council area or dump point before opening the outlet. If the facility doesn’t clearly say it accepts grey water, keep the tank closed and ask the operator. Local requirements differ, so there isn’t one disposal rule you can safely apply across Australia.

Public dump points are the normal disposal network for toilet waste. In August 2023, Camps Australia Wide reported that most Australian public dump points were free, although some charged a fee or requested a donation. Its app also lists dump point locations around the country.

Keep fresh-water equipment away from anything used for waste. Camps Australia Wide says never to fill a fresh tank from a dump point hose and advises keeping fresh and waste hoses separate to prevent cross-contamination.

Don’t put wet wipes or other non-biodegradable material into a dump point. Camps Australia Wide warns that these items cause blockages. Public dump points generally provide a hose or tap for rinsing the emptied cassette, but that equipment remains part of the waste area.

Is a cassette or composting toilet better in a HiAce?

A portable cassette toilet is the more practical choice for many HiAce layouts because it costs less and occupies less space than the composting unit compared here. A composting toilet suits longer stays when its longer solids-emptying interval justifies the price, height, ventilation and power needs.

The figures below come from the Australian product listings for the $270 Thetford Porta Potti 365 and the $1,895 Nature’s Head composting toilet.

Option	Listed price	Width	Height	Depth	Waste capacity or interval	Separate tank
Thetford Porta Potti 365	$270	383mm	414mm	427mm	21L	15L flush
Nature’s Head	$1,895	450mm	546mm	475mm	~80 uses	8.5L urine

At the listed prices, the Nature’s Head costs $1,625 more than the Porta Potti, based on figures from Thetford Australia and Nature’s Head Australia. That difference buys a different waste-handling system, not more room inside the van.

The portable unit weighs 4.0kg empty and Thetford offers a hold-down kit to secure it in transit, according to its Australian listing. You still need clearance to lift and carry its lower tank without dismantling the bed or kitchen.

Nature’s Head says its solids chamber lasts for about 80 uses, while its 8.5-litre urine bottle should be emptied every 24 to 48 hours, according to Nature’s Head Australia. The toilet also needs a 12V connection for its extraction fan and comes with venting and mounting hardware.

Best for compact HiAce builds: the portable cassette toilet, provided you can reach dump points often enough. The composting option better suits a permanent fit-out with room for its larger shell, a vent route and an electrical connection.

What does self-contained mean for campsite access?

Self-contained access means meeting the written conditions of the campsite you want to use, not merely carrying a portable toilet. Your HiAce needs a workable plan for fresh water, grey water and toilet waste that keeps each stream contained until you reach an accepted disposal point.

Don’t confuse vehicle approval standards with campsite entry rules. The federal model report standards compiled in September 2023 specify at least 50 litres of potable water storage for campervans covered by that approval route. Meeting that figure alone doesn’t require a campsite operator to admit the van.

Check the booking terms before building around the self-contained label. One site may focus on a toilet, while another may also require enclosed grey-water storage, rubbish capacity or particular equipment. If the operator publishes a capacity or certification requirement, that wording decides whether your setup qualifies.

A sensible pre-booking check covers:

• A securely mounted fresh-water supply that remains separate from waste equipment.
• A closed grey-water tank with enough capacity for the planned stay.
• A toilet that can be secured while the HiAce is moving.
• A way to remove stored waste without spilling it inside the van.
• A confirmed disposal stop that accepts the type of waste you carry.
• The campsite’s current written conditions for self-contained vehicles.

A portable toilet and a 50-litre water system suit two people taking short trips near regular service points, using the drinking-water allowance from Parks Victoria. A larger fixed system makes sense when you stay away longer, but only after checking the space and remaining payload.

Not for travellers unwilling to store waste until an accepted facility is available: a self-contained setup doesn’t make waste disappear. It gives you a controlled way to hold it between stops.