Gas gets talked about less than electrics aboard, but its consequences are harder. LPG is heavier than air: a leak does not rise, it sinks into the bilge and collects there. That is the essential difference from mains gas ashore, and the reason behind every rule on a boat.
1. Why It Is Its Own Subject
Propane and butane are roughly 1.5-2 times heavier than air. A leak runs to the lowest point on board: the bilge, an enclosed space with no ventilation. Gas collecting there needs only a switch closing or a spark.
So a gas installation aboard has a single purpose: if it leaks, it must be able to get out.
2. The Gas Locker: Three Rules
| Rule | Why |
|---|---|
| Gastight, opening only from the top | A locker that opens sideways releases a leak into the boat. With the lid on top, gas cannot get in. |
| Floor drain above the waterline, open overboard | Being heavy, gas sinks to the floor and drains out. A blocked drain, or one leading to the bilge, makes the locker pointless. |
| No electrics inside | No lighting, no socket, no cable run. A source of ignition does not share a space with gas. |
The drain is the first thing a surveyor looks at. Finding it plugged, hosed off or taped over is not rare, and it defeats the whole installation.
3. Hose, Pipe and Connections
- Read the marking. Gas hose carries a standard number and date. Common practice is renewal every five years; a hose whose marking cannot be read is treated as old.
- Keep free lengths short. Hose is for moving connections only (cylinder outlet, appliance inlet); runs between are copper or steel.
- Copper must be soft and seamless, not led over sharp edges, clipped where it can vibrate.
- Connections must be reachable. A union behind a closed locker cannot be checked.
- Cracking and hardening: if flexing the hose by hand shows crack lines, its life is over.
4. Valves: Three Separate Shut-Offs
- Cylinder valve: closed when leaving the boat and after every use.
- Main shut-off: inside the cabin, within reach. Position and operation are checked in survey.
- Appliance valve: hob, oven, heater, each with its own valve, individually closable where there is more than one.
The right order for shutting down the hob: close the cylinder valve first, let the flame burn out on its own, then close the hob knob. That leaves no gas in the line.
5. Detectors and Safety Devices
- A gas detector belongs at bilge level, not on the deckhead. Heavy gas collects low; a detector high up sees nothing.
- Flame failure device: modern hobs cut the gas if the flame goes out. Older hobs do not; its presence is recorded.
- Solenoid valve: an electrically operated valve on the panel lets you cut the line without going to the cylinder. Not mandatory, but a practical extra layer.
- A carbon monoxide detector is separate. A gas detector does not measure CO, which is colourless and odourless; heaters, generators and a neighbour's exhaust are all sources. Sleeping areas need a CO detector of their own.
6. Ventilation
A gas appliance consumes oxygen and produces combustion products. Running the hob long in a closed cabin means both CO risk and condensation.
- Keep a hatch or port open while cooking.
- Never use the hob to heat the cabin, a known cause of CO poisoning.
- Do not block permanent vents; a vent taped over for winter produces mould and risk together.
7. What Goes in the Report
| Class | Example finding |
|---|---|
| A, Safety | Locker drain blocked; electrical connection inside the locker; cracked hose; main shut-off unreachable. |
| B, Near term | Hose past its marked date; no detector or one fitted at the wrong height; appliance valve missing. |
| C, Observation | Regulator ageing but functional; locker lid seal worn. |
The report also states plainly that leak measurement and pressure testing were not carried out, and should be done by a qualified fitter where indicated.
8. When Buying
- Ask when and by whom the installation was done; request documents if they exist.
- Appliances added later (oven, heater, outdoor galley) change the installation, every addition after the original build is checked.
- Check that the cylinder size and type suit the locker; a bottle kept outside because it will not fit invalidates the installation.
- A gas fault need not change a purchase decision, most items are relatively cheap and definitively fixable. What matters is not going to sea before they are closed.
9. Electric Alternatives
Induction hobs and electric water heating are spreading alongside lithium systems. They remove gas risk entirely but require the energy budget to be built from the start: an induction hob draws 1500-2000 W instantly, which means inverter capacity, cable section and battery bank. If you are considering it, the lithium conversion page covers the energy side.
Frequently Asked Questions
Scope: The survey is non-destructive and nothing is dismantled; details on the survey types page.
Findings we often see on site
- Out-of-date gas hose, blocked locker drain: The gas hose is well past its manufacture date and the gas locker drain is blocked.
Related Pages
A survey covers locker, drain, hose and valve arrangement; a qualified fitter is coordinated where needed.
💬 WhatsApp 📝 Written quote 📞 +90 501 5 SURVEY