Measure before sizing
Run the intended process with measured containers or a meter. Record normal use and a poor-case job. Multiply by jobs between refills, then add a modest contingency rather than an arbitrary oversized tank.
- Measure exterior and interior water separately
- Model the longest realistic run between refills
- Keep a written assumption for seasonal or service changes
Water dominates payload quickly
Every litre adds about one kilogram before the tank, frame, hose reel and pump. The plated payload also has to carry people, fuel where applicable, chemicals, machines and personal items.
- Use the vehicle’s actual plated limits
- Count passengers and everything normally carried
- Weigh the finished vehicle and check individual axles
Flow path matters
Outlet size, valves, filters, hose bore and pump position can restrict supply. Design for inspection and drainage, and have permanent mounts assessed by a competent installer.
- Use components rated for the liquid and pressure
- Make filters and shut-offs accessible
- Secure the full tank for braking and cornering loads
Compare the workable approaches
| Approach | Best for | Check before buying | Main trade-off |
|---|---|---|---|
| Portable containers | Cars and early validation | Safe lifting, caps and containment | Frequent handling and limited volume |
| Low-profile tank | Small vans and mixed utilities | Baffles, fixing points and outlet access | Uses valuable floor area |
| Large baffled tank | High-volume independent rounds | Payload, axles, frame and installation | Heavy even before equipment is loaded |
Retailer shortlist
Compare products against the specification.
These broad Amazon UK searches are a starting point, not a claim that every result is compatible. Open the data sheet and confirm the listed checks before buying.
Baffled water tanks
Compare capacities only after calculating litres per run and remaining vehicle payload.
Check: Empty weight, baffles, outlet size, mounting guidance and usable dimensionsCompare Baffled water tanks on Amazon UK12V water pumps
A pump must match the tank outlet, hose path and pressure-washer inlet requirement.
Check: Flow, pressure, duty cycle, fuse, current draw and dry-run protectionCompare 12V water pumps on Amazon UK