Diesel Heater Fuel Tank — External Upgrade Tank for Webasto & Chinese Diesel Heaters

This is the tank that replaces the one your heater came with. Three plastic sizes ship from stock — 8L, 10L and 12L — and larger capacities, stainless steel and aluminum are built to order.

Most diesel heater kits include a thin can that runs dry before morning. The stock Webasto and Eberspacher 10 litre tank is better made, but it costs about as much as this one. It also vents through a single pinhole in the cap. Both leave you refilling in the dark.

An external fuel tank gives your heater its own supply, separate from the vehicle tank. You bolt it down once and top it off in seconds. Below is exactly what ships, what it costs, and what arrives in the box.

What Ships From Stock: 8L, 10L and 12L Diesel Heater Fuel Tanks

Three plastic sizes are in stock and ship within 3 days. All three are black three-layer PE with a base-mounted outlet, a vented cap, and a way to read the fuel level without a dipstick.

Runtime depends on the heater and the setting, not just the tank. A 2.5KW diesel air heater burns 0.14–0.25 L/hr; a 5KW unit burns 0.20–0.48 L/hr flat out.

• 8L — about 32 hours on a 2.5KW at medium, about 17 hours on a 5KW running hard.
• 10L — about 40 hours at medium, about 21 hours flat out.
• 12L — about 48 hours at medium, about 25 hours flat out.

Those hours assume the tank holds what the label says. Ours do — see the capacity section below.

Replacing a Webasto or Eberspacher Fuel Tank

These tanks are a straight replacement for the plastic 10 litre tank sold for Webasto and Eberspacher air heaters. You keep your existing fuel pump and dosing line; only the container changes.

The stock part is sold as tank 33000110 / 221000202800, fits both brands, and lists at about £85 including VAT in the UK. It measures 410 × 410 × 86 mm and weighs 1.6 kg with fittings. Our 8L is 368 × 337 × 86 mm — the same 86 mm depth, in a smaller footprint, so it drops into the same kind of space.

What changes when you swap:

• Same connection — a barbed outlet at the base takes the standard fuel line that came with your heater. No adapter hunting.
• A cap you can lock — the stock tank has no keyed option. Ours does, on every size.
• A fuel level you can actually read — a translucent window with a printed scale on the 8L, an external sight tube on the 12L.
• Eight spread mounting points on the 8L instead of one bracket at each end, so vibration load does not concentrate on a corner.

The same swap works on Autoterm and Planar units, and on the Chinese heaters sold through Amazon and eBay. Units advertised as 8KW are covered too — they run the same hardware as a 5KW and draw fuel at the same rate. In the UK these are usually called night heaters, and the fuel tank is the same part either way.

You will also see this part listed as a parking heater fuel tank, an auxiliary fuel tank, an extended fuel tank or a diesel heater gas tank. Same component, different names. None of them mean petrol — diesel only, in every size we sell.

The Cap Is the Part That Fails

On the tanks these replace, the cap vents through a single pinhole — and that pinhole causes two of the most common complaints owners post about.

It blocks. Dirt, wax or ice closes the hole. The tank pulls a vacuum as fuel draws down, the pump starves, and the heater flames out. Owners spend money on pumps and glow plugs chasing a fault that was a blocked vent.

It weeps. A pinhole in the top of a cap will pass fuel when the tank is full and the vehicle is on a slope or a rough road. Van builders on the forums 3D-print vent adapters and plumb remote vent lines to get around it.

Both of our caps are vented — the standard cap and the keyed locking cap alike — so the pump never fights a vacuum whichever you choose. Keep the vent clear on any tank you own, and check it first when the heater misbehaves.

The locking cap, and why it costs a few dollars more

Choose the keyed locking cap and only you can open the tank. It stops siphoning in a car park, at a trailhead, or on a site overnight, and it stops anyone dropping something into your diesel.

Keys are supplied with the cap. On the 8L and 10L the lock adds about $11–14; on the 12L it is fitted as standard. Skip it if you park private and secure.

A 10L Tank That Holds 10 Litres, in Black

A tank marked 10L here holds a true 10 litres. Plenty of cheap tanks carry an inflated label and hold closer to 8 — which quietly breaks every runtime calculation you make from it. If you plan an overnight run on the number printed on the tank, the number has to be real.

The body is black on purpose. Translucent and white tanks let UV through, and two things follow from that.

• The plastic ages. Caravan owners report white tanks turning beige and going brittle. The usual fix — spray it black — peels off within a season.
• The diesel ages. Light drives oxidation in the fuel, which matters most in a heater tank because it often sits part-used for months between trips.

We used to sell a white 5L and a white 15L. Both are discontinued, and UV is the reason. The level window on the black tanks is the only translucent part — enough to read the fuel, small enough not to light up the whole tank.

If your tank has to live in full sun year-round, a fitted cover still helps. Black PE already does most of that work, so a cover is a refinement here rather than the repair job it becomes on a white tank.

Black PE also handles the things metal does not. It cannot rust from the inside and flake into your fuel filter, and it does not sweat condensation into the diesel the way a cold steel wall does. If you want a metal shell for a permanent exterior install, that is a built-to-order stainless tank — covered further down.

Why the 12L Costs Twice What the 10L Costs

The 12L is not a bigger 10L. It is a different tank, and the price reflects the build rather than the two extra litres.

• Thicker wall section — more material, aimed at daily winter use and permanent installs rather than weekends.
• External sight tube — a tube running outside the tank wall, not a window in it. You read the level from a distance without opening anything.
• 45° angled filler neck — you can pour into it in a tight bay without a funnel fighting you.
• Keyed locking cap fitted as standard — on the other two sizes it is a paid option.

At $232.99 it sits where heavy-duty 12L tanks sit in this market. If you want capacity rather than build, the 10L at $108.56 is the better buy, and two 10L tanks cost less than one 12L. Order the 12L when the tank lives outside, gets filled in the dark, and has to be right for years.

What Arrives, What It Costs, and When

Every order ships within 3 days of payment and arrives in about 7–12 days. Shipping is already in the price — nothing is added at checkout.

In the box:

• The tank in the size you chose, black three-layer PE
• Cap — standard vented, or keyed locking with keys, depending on the option you pick
• Barbed fuel outlet at the base of the tank

You keep your heater's original fuel pump, dosing line and filter. Nothing else in the fuel system changes, which is why a tank is the cheapest worthwhile upgrade on a budget heater kit.

Every tank carries a 1-year warranty. If something is wrong with it, message us and we will make it right.

Built to Order: 5L, 15L, 20L, 30L, Stainless Steel and Aluminum

Anything outside the three stock sizes is a made-to-order build, including every metal tank. There are no photographs of these because each one is built to a drawing.

• Plastic in 5L, 15L, 20L and 30L — the sizes people ask for when a 12L still means refilling more often than they want.
• Stainless steel — welded cylinder or rectangular box, with mounting feet and strap clamps. This is the answer for permanent exterior installs and for anywhere a plastic tank is not appropriate.
• Aluminum (aluminium) to your drawing — send dimensions and outlet positions and we build to them.

Made-to-order tanks need a lead time and a minimum run, and they are quoted rather than listed. Send your heater model, the space you have to fill, and the capacity you want; you get a drawing and a price back.

Want the full comparison of black plastic, white plastic and stainless before you decide? Our engineering site has the longer write-up: diesel fuel tank selection guide.

Boats: Read This Before You Order

A plastic diesel heater fuel tank is not the right part for a permanent installation on a boat. We would rather say that here than take the order.

The equivalent stock tank for Webasto and Eberspacher heaters is sold with the note "not suitable for marine applications," and the reasoning applies equally to ours. These tanks are not certified to a marine fire-resistance standard, and they have no deck fill or overboard vent.

ABYC A-7 is the US recommended practice for boat heating systems. It expects the heater to draw from a permanently installed tank with a deck fill and an overboard vent. ISO 10088 and Transport Canada point the same way. A vented plastic tank sitting in a locker meets none of that.

What to do instead:

• Permanent install on a boat — specify a made-to-order stainless tank and have it installed to your local rules. Message us before you order and we will quote it.
• Draw from the boat's own diesel tank — a VVKB fuel tank standpipe lets the heater feed from the existing tank without a second container.
• Choosing the heater itself — see the 12V marine diesel heater, which ships with the marine-specific parts a truck kit does not include.

Vans, campervans, caravans, motorhomes, trucks, trailers and job sites are what these tanks are built for, and there the plastic tank is the right answer.

If You Landed Here Looking for Something Else

Two products share almost the same name as this one, and people arrive here meaning one of them.

• A heater that warms your diesel. If your fuel gels in cold weather and you want to heat the tank rather than store fuel in one, that is a diesel fuel tank heater. Different product, different job.
• A heater with an internal fuel tank. If you want the tank built into the unit rather than bolted beside it, that is a portable diesel heater. It carries its own fuel on board.
• A bulk or onsite fuel tank — we do not sell jobsite bunded tanks or transportable bulk fuel storage. These are vehicle-scale tanks, 5–30 litres.

Also on this site: diesel heater exhaust pipe, diesel heater glow plug, and the full VVKB heater parts range.

Frequently Asked Questions

Will this fit my Webasto or Eberspacher heater?

Yes. It replaces the plastic tank sold for Webasto and Eberspacher air heaters, and connects with the standard fuel line that came with your heater. It also fits Autoterm, Planar and the Chinese diesel heaters sold on Amazon and eBay. You keep your existing fuel pump and dosing line.

My heater keeps flaming out. Could the tank be causing it?

It can, and it is the cheapest thing to rule out. If the cap vent is blocked, the tank pulls a vacuum as fuel drains and the pump starves. Next time it cuts out, crack the fuel cap open — if the heater restarts and keeps running, the vent is your fault, not the pump.

Why does the area around my tank smell of diesel?

Usually the cap. Tanks vented by a bare pinhole in the top face let vapour out continuously, so any enclosed space around them starts to smell. They can also weep fuel when full on a slope. Mount the tank in an outside locker, under the vehicle, or in a truck bed rather than a sleeping area. If it has to sit inside, route the vent to outside air.

Does the locking cap starve the pump of air?

No. Both the standard and the keyed locking cap are vented, so air replaces the fuel as it draws down. Keep the vent clear either way — a blocked vent creates suction inside the tank that stops fuel flow regardless of which cap you have.

Is a 10L tank really 10 litres?

Yes, a true 10 litres. Many cheap tanks are labelled 10L and hold closer to 8 behind an inflated number, which quietly breaks the runtime you planned. Ours hold their rated capacity, so the hours you calculate are the hours you get.

How long will each size run my heater?

At a medium setting on a 2.5KW heater, roughly 32 hours on 8L, 40 hours on 10L and 48 hours on 12L. A 5KW heater running hard burns up to 0.48 L/hr, which cuts those figures to about 17, 21 and 25 hours. Size up if you are heating a large caravan or leaving the heater unattended.

Why is the tank black instead of see-through?

UV. Translucent and white tanks go brittle and discolour in sunlight. Light also accelerates oxidation in the diesel, which matters because heater tanks often sit part-used for months. We discontinued our white 5L and 15L tanks for exactly this reason. The level window is the only translucent part, so you can still read the fuel without lighting up the whole tank.

I can see bubbles in the fuel line. Is that normal?

Small bubbles roughly half an inch apart are normal on these systems. More bubbles than that point to a small air leak between the tank and the pump. Very large bubbles mean a bigger leak, or that the tank is running dry. Check every joint is airtight, then prime by running the pump into a clear jar until fuel flows with no bubbles.

Can I use this tank on a boat?

Not for a permanent installation. Plastic heater fuel tanks are not certified to marine fire-resistance standards, and they have no deck fill or overboard vent. That is what ABYC A-7 and ISO 10088 expect of a boat heating system. For a boat, ask us to quote a made-to-order stainless tank, or feed the heater from the vessel's own diesel tank with a standpipe.

Where should I mount the tank?

Tank location matters more than bracket choice: mount it at or slightly above your heater's fuel pump, and within a few feet of it. The pump can lift fuel, but a short line that rises gently primes fastest and holds prime best. Bolt it down through the pre-drilled holes rather than using a strap bracket. A full 12L tank moving on a rough road will find the weak point in any strap.