Every part of a conversion, three ways.

EMPTY weight only. FULL = empty + capacity_l x 1kg. 1L = 1kg — the biggest hidden payload killer.

• Budget

  Jerry cans / portable (2x 20L)

  generic

  2 kgest.≈ £30

  40 L capacity — counts as 40 kg when full

  Lightest, flexible, no plumbing. 2kg empty but 42kg full. Refill anywhere. Great for weekenders.

• Mid

  Fiamma 70L onboard fresh tank

  Fiamma

  3 kgest.£58

  70 L capacity — counts as 70 kg when full

  Classic van fresh tank. 3kg empty but ~73kg FULL — dominates payload. Consider part-filling.

• Mid

  Underslung fresh tank (60-90L)

  CAK/generic

  5 kgest.≈ £180

  75 L capacity — counts as 75 kg when full

  Under-chassis, saves interior space. Empty ~5kg, full ~80kg — slung low (good CoG). Needs frost protection.

• Mid

  Grey waste tank (40-70L)

  generic

  4 kgest.≈ £120

  50 L capacity — counts as 50 kg when full

  Collects used water. Fills as fresh empties, so combined water weight stays ~constant in use.

Sink, tap, fittings, hose runs.

• Budget

  Sink + folding tap + pipework

  generic

  3 kgest.≈ £70

  Sink, tap, John Guest fittings, hose runs, strainer.

• Mid

  Combi hob/sink + mixer tap + fittings

  Dometic/Smev

  5 kgest.≈ £220

  Glass-lid combi hob/sink saves space; better mixer. (Hob cross-refs Cat 8.)

Empty weight; holds its own water. Gas types need Gas Safe sign-off.

• Budget

  Truma Therme TT2 (5L electric)

  Truma

  2 kg✓ verified≈ £150

  5 L capacity — counts as 5 kg when full

  5L hot water for hands/dishes, 300W + uses air-heater warmth. Not enough for a shower. Empty ~2kg.

• Mid

  Truma electric water heater (14L)

  Truma

  3 kg✓ verified≈ £330

  14 L capacity — counts as 14 kg when full

  14L mains-electric, shower for two. Empty ~3kg, ~17kg full. Needs 230V/hook-up or big power.

• Premium

  Diesel water heater / combi (Autoterm Flow / Truma Combi)

  Autoterm/Truma

  7 kgest.≈ £900

  10 L capacity — counts as 10 kg when full

  Heats water (+ often air) off diesel. Best all-round off-grid hot water. Combi replaces a separate air heater.

• Premium

  Truma Ultrastore BGE 10 (gas+electric)

  Truma

  6 kgest.≈ £400

  10 L capacity — counts as 10 kg when full

  Needs qualified sign-off (gas/electrical)

  10L gas+electric combi — best for off-grid showering (gas heats without hook-up). Gas Safe sign-off.

12V pressurised or submersible pump.

• Budget

  Submersible 12V pump

  Whale/generic

  0.5 kgest.≈ £20

  Cheapest, sits in tank. Fine for a single tap. Lower pressure.

• Mid

  Shurflo diaphragm pump + accumulator

  Shurflo

  1.5 kgest.≈ £90

  Standard pressurised 12V system, ~3 GPM, auto on/off. Add silencers. Reliable/recommended.

Hardware only; REAL weight is the 70-100L+ tanks + water heater it forces (Cat 6).

• Premium

  Wet-room: tray + wet-wall + mixer + drain + extractor

  generic

  15 kgest.≈ £400

  Weight sits high — raises the centre of gravity.

  Enclosure hardware. Real weight is what it forces: 70-100L+ fresh+grey tanks + water heater (Cat 6). Needs waterproofing.

Rear/side hot-feed point. Light, no wet-room.

• Budget

  Outdoor shower point (hose + inline heater)

  generic

  2 kgest.≈ £120

  Rear/side hot-feed shower off your water heater or solar bag. Light, simple.

Heaviest toilet hardware but no waste-water weight — payload advantage for full-timers.

• Mid

  Budget separating composting (Boxio/OGO-style)

  Boxio/generic

  6 kgest.≈ £180

  Compact urine-separating toilet at a fraction of premium price. Lighter, smaller capacity.

• Premium

  Nature's Head / Air Head composting

  Nature's Head/Air Head

  13.2 kg✓ verified≈ £950

  No chemicals/black water, separates urine/solids, fan-vented. Heaviest hardware but no waste-water weight.

Light empty; flush/waste tanks add ~15-20kg full.

• Mid

  Dometic 976 portable

  Dometic

  4 kgest.≈ £110

  Compact chemical toilet with level gauge, pressurised flush, low water use.

Adhesive/frame-out/trim/sealant. Waterproofing is critical.

• Budget

  Bonding kit / timber frame-out + trim + sealant

  Sika/generic

  2 kgest.≈ £40

  Weight sits high — raises the centre of gravity.

  Urethane adhesive + primer (glass) OR timber frame-out (Seitz on panel vans) + trim. Waterproofing critical.