Leaks usually happen at transitions: pump to pipe, pipe to heater, hose to tank, or tube through a moving cabinet. A reliable design reduces transitions, uses matched parts and keeps unavoidable joints visible.
Choose one documented pipe system
Select from the requirements, not colour:
- approved/intended for potable water;
- rated above the maximum cold and hot temperature;
- rated above pump shut-off and possible thermal pressure;
- compatible with the exact fittings, inserts and seals;
- supported for vibration and vehicle movement;
- available in replacement sizes where you travel.
John Guest markets a 12mm mobile-home and caravan system using matched pipe and fittings for leisure-vehicle water. This is an example of a documented family, not evidence that every 12mm product interchanges.
Never force 1/2-inch tube into a 12mm fitting or assume a brass adapter shares the same sealing method. Keep the product codes and technical sheets in the build record.
Use hose only where it has a job
Flexible reinforced hose suits pump vibration sections, removable containers and some tank connections when approved. It can kink, soften, retain odour and require clamps. Semi-rigid pipe creates neat supported routes and reliable matched fittings but can transmit vibration if connected directly to a pump.
Follow the pump guide: if the manufacturer specifies flexible inlet and outlet connectors, install them and anchor the change to rigid pipe. Use suction-rated hose before the pump so it cannot collapse.
Series or manifold layout
Branched/series
One main line passes outlets with tees.
Advantages: less tube, compact and economical.
Risks: hidden tees, shared pressure loss and harder isolation.
Manifold/home-run
Each outlet receives a direct line from a central manifold.
Advantages: individual isolation, fewer concealed branch joints and clearer diagnosis.
Risks: more tube, larger service cabinet and manifold cost.
For a sink-only van, a short series route can be excellent. A kitchen, shower, exterior rinse and heater often justify a labelled manifold. Choose the scheme that keeps joints and valves accessible rather than the one that looks impressive in a diagram.
Route for drainage and protection
Create a measured overlay with plumbing, electrical, heater ducts and furniture fixings. If those systems are being professionally installed, compare relevant campervan builders before the walls close. Apply these rules:
- keep runs short and direct;
- slope deliberately towards defined low-point drains where feasible;
- eliminate capped dead legs;
- protect every penetration with a suitable grommet or sleeve;
- support tube at the system maker's intervals and near fittings;
- leave controlled movement for temperature and vibration;
- keep joints away from electrical equipment;
- maintain access to pump, strainer, heater, valves and filters;
- separate pipe from heater exhaust and hot ducts by required clearances;
- photograph routes with a tape measure before closing walls.
The HSE's hot and cold system guidance favours short direct pipe and removal of dead ends to reduce stagnation. A campervan is different from a managed building, but trapped unused branches are still poor hygiene and winter-drain design.
Make push-fit joints correctly
Use the exact system instructions. A typical process is:
- cut square with a dedicated tube cutter;
- inspect for scratches, ovality or burrs;
- fit the specified insert where required;
- mark insertion depth;
- push straight to the full stop;
- pull back gently to confirm engagement;
- fit a locking clip where the maker provides one;
- support the tube without side-loading the connector.
Do not use lubricant, sealant or PTFE tape unless the fitting instructions call for it. Push-fit tube seals on an internal O-ring; scratched tube or shallow insertion can leak later even if it survives the first fill.
For threaded joints, identify whether the seal is a taper thread, parallel thread plus washer, swivel cone or bonded seal. Tape is not a universal repair. Over-tightening plastic ports can crack pumps and heaters.
Tank, fill and vent pipework
The fill and vent are usually larger than distribution pipe. The vent must pass air as fast as filling displaces it and as the pump removes water. Avoid sags that trap water and route openings against dust, insects and road spray according to the tank system.
Provide a full-bore tank isolation valve, lowest drain and accessible connection. Check that a drain can actually empty the tank when the vehicle is level and that the outlet does not discharge onto brakes, exhaust or electrical hardware.
Use only potable-rated fill hose and a sanitary external connection. Keep the dedicated fill hose capped and separate from toilet-service items. Review the full arrangement in the water-system guide.
Hot-side details
Check the temperature rating of tube, fittings, mixer and flexible connectors. Provide every heater-required check valve, expansion accommodation, pressure reducer, relief and drain component. Do not trap a relief discharge or cap it.
Keep hot runs short. Long pipe wastes fresh and grey capacity while the occupant waits for heat. Insulate with a compatible material without hiding inspection points. Use the hot-water comparison to decide whether a fixed hot circuit is justified at all.
Staged testing
Dry inspection
Check insertion marks, clips, supports, chafe points, valve direction and drain falls. Photograph every connection.
Cold pressure test
Fill from a safe source, purge air, run the pump to shutoff and switch it off. Dry every joint, then inspect with clean tissue. Leave pressurised only for the period and pressure allowed by the component instructions. A pump that restarts with all outlets shut indicates pressure loss.
Operational test
Run every outlet alone and together. Check fill/vent behaviour, pump noise, grey drainage and low-point drains. Move mixer and isolation valves through every normal state.
Hot test
Commission the heater exactly as instructed. Inspect joints from cold through full operating temperature and cool-down because thermal movement can reveal leaks.
Road test
Drive with a realistic partial tank over normal rough surfaces. Reinspect supports, fittings and cabinet penetrations. Repeat after the first long journey.
Service kit and records
Carry only parts compatible with the installed family:
- spare straight connector and end stop;
- short length of matching tube;
- correct cutter and release tool;
- pump-port seals and strainer washer;
- labelled valve diagram;
- absorbent cloth and leak-detection plan.
An emergency end stop can isolate a damaged branch, but only if valves and joints are reachable. The permanent quality of the system comes from compatibility, support and inspection—not a box of random adapters.
Make every pipe drainable before frost
Map low points, heater bypass, filters, taps and pump so no hidden branch remains full during storage.
Frequently Asked Questions
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