Tapping directly into your van's diesel fuel tank to feed a diesel heater is the cleanest, most reliable fuel supply method. Here is everything you need to know about doing it safely on a UK campervan.
Verdict
Tank tapping is the best way to fuel a diesel heater — no refilling, no diesel cans, no running out at 2am. Use the sender unit access hole, do not drill the tank. Use a proper pick-up kit (£35-40 for most vans). Seal the grommet properly with Hylomar. Check your insurance policy before modifying the fuel system. The DIY job is straightforward on a Transit or VW T5/T6.
Why Tap the Tank?
A diesel heater can be fuelled in three ways:
| Method | Pros | Cons |
|---|---|---|
| Separate diesel can (2-5L) | Simple, no vehicle modification | Running out at 2am, refilling every 3-4 days, storing diesel inside |
| Plumbed into filler neck | Easy access, no drilling into tank | Prone to air locks, fuel line routing is awkward, looks messy |
| Tank tapping (direct pick-up) | Inexhaustible supply, clean, professional install | Requires drilling the tank, higher risk if done wrong |
| Tank tapping gives you access to the van's 60-80L fuel tank. A diesel heater burns 0.2-0.4L per hour. You can run the heater 24/7 for 150-400 hours on one tank of fuel. You will fill up at the pump before the heater runs out. |
How Tank Tapping Works
The process is straightforward:
- Locate the sender unit access hole. Most vans have an access panel under the floor or under the rear seats. This gives you access to the top of the fuel tank and the sender unit.
- Remove the sender unit. The sender unit is a plastic disc on top of the tank with wires (fuel gauge) and the main fuel pick-up pipe. Unscrew the retaining ring (a brass ring tool is £15 on Amazon).
- Fit the pick-up pipe. The heater pick-up kit includes a brass or stainless steel pipe that slots through the same grommet as the main fuel pick-up. The pipe extends to within 10mm of the tank bottom (to pick up fuel even when the tank is low).
- Connect the fuel hose. The pick-up pipe has a barbed fitting for 6mm or 8mm fuel hose. Run the hose to the diesel heater's fuel pump. The pump pushes fuel to the heater.
- Seal everything. The grommet around the sender unit must be re-sealed with a fuel-resistant sealant (Hylomar or Wellseal, not silicone).
Van-Specific Considerations
Ford Transit (2006+)
The sender unit is under a metal plate in the floor behind the driver's seat. Remove the plate (6 bolts). The sender unit is accessible. Plenty of room for a second pick-up pipe. This is the easiest van to tap.
Mercedes Sprinter / VW Crafter
The sender unit is under a panel in the floor between the driver and passenger seats. Access is tight — you might need to remove the seat base (4 bolts). The tank is made of plastic, which is easier to drill than metal.
Fiat Ducato / Citroen Relay / Peugeot Boxer
The sender unit is under the passenger seat. Remove the seat (4 bolts). The access panel is a round plastic cover (turn to unlock). The tank is plastic. The fuel pick-up is a combined unit — you might need a specific Ducato tank tapping kit from Butler Technik (£35).
VW Transporter T5/T6
The sender unit is under a panel behind the driver's seat. Access is good. The tank is plastic. VW sell an official fuel pick-up kit for auxiliary heaters (part number 7H5 919 511, £45). This is the safest option.
Risks and How to Avoid Them
| Risk | Consequence | Prevention |
|---|---|---|
| Drilling into the tank | Fuel leak, fire hazard | Never drill the tank. Use the sender unit grommet. |
| Debris in the tank | Blocked heater fuel filter | Clean the sender unit area thoroughly before opening. Use a new pick-up pipe. |
| Air leaks in the pick-up | Heater runs rough, stops | Use a fuel-rated hose with jubilee clips. Seal the grommet. |
| Pick-up pipe touching the bottom | Sediment sucked into the heater | Leave 10mm gap between the pipe end and the tank bottom |
| Incorrect sealant | Fuel leaks, diesel smell in the van | Use Hylomar or Wellseal. Never use silicone (fuel dissolves it). |
Professional vs DIY
| Factor | Professional Install (£150-250) | DIY Install (£35-60) |
|---|---|---|
| Parts cost | Included | £35-60 (pick-up kit + hose) |
| Time | 1-2 hours | 1-3 hours |
| Warranty | Usually 12 months | None |
| Insurance impact | Professional install may satisfy insurer | DIY may require notification |
| Risk | Low (experienced fitter) | Higher (depends on your skills) |
| Insurance: Most UK campervan insurers (Comfort, Brentacre, Adrian Flux) require notification of any modification to the fuel system. Some accept a DIY install if it is done with a certified kit. Some require a professional install. Check your policy before tapping the tank. |
The Pick-Up Kits
| Kit | Price | Fits |
|---|---|---|
| Autoterm Diesel Pick-Up Kit | £40 | Most vans, 6mm pipe |
| Butler Technik Ducato Kit | £35 | Fiat Ducato / Peugeot Boxer |
| VW Genuine T5/T6 Aux Heater Kit | £45 | VW Transporter T5/T6 |
| Planar Universal Pick-Up Kit | £38 | Universal, 8mm pipe |
| Chinese diesel heater pick-up set | £12 | Universal, cheap, works fine |
