RV Propane Safety: Tanks, Leaks and Detectors

Propane runs the stove, the furnace, the water heater and often the refrigerator in most used RVs. The system is simple in outline and unforgiving in detail: a leak, an overfilled cylinder or a dead alarm can turn a normal trip into an emergency. This guide explains how the parts fit together, what to check on a used RV before you buy it, how refilling and requalification work, and when to stop and call a qualified RV technician.

How the propane system is laid out

Propane is stored as a liquid under pressure. It boils to gas as you draw it off, and the gas is heavier than air, so it collects low. That is why an RV has an LP gas detector near the floor and why a smell test at floor level matters.

A typical system has four parts:

• The tank or cylinder, holding the liquid.
• A regulator, reducing tank pressure to the low pressure the appliances use.
• Lines and fittings, carrying gas to each appliance.
• The appliances, each with its own burner or pilot and safety controls.

An added odorant gives propane a smell like rotten eggs. If you smell it, treat it as a real leak until a qualified RV technician proves otherwise.

ASME tanks vs DOT cylinders

Motorhomes usually have a permanently mounted ASME tank filled in place. Trailers usually carry removable DOT cylinders, commonly two 20-pound or 30-pound cylinders on the tongue. The two are regulated differently, and the refill routine differs.

OPD valves and requalification dates

Since 2002, DOT propane cylinders of 4 to 40 pounds must have an overfill prevention device (OPD) to be refilled. You can recognise one by the triangle-shaped valve handwheel. A cylinder without it should not be filled.

A DOT cylinder must be requalified 12 years after its date of manufacture and at set intervals after that. An out-of-date cylinder should not be refilled. The date is stamped on the cylinder collar; check it before you buy a used trailer, because replacing cylinders adds to the cost of getting the RV ready.

Tanks and cylinders are filled to about 80 percent of capacity, leaving room for the liquid to expand. An overfilled cylinder has no room for that expansion and can release liquid propane instead of gas.

Checking a used RV’s propane system before you buy

A used RV’s propane system is one of the few areas where a problem can hurt you, not just cost you money. Put it on your used RV inspection checklist alongside water damage and tires.

What to look at:

• The tank or cylinders. Look for rust, dents, a missing or damaged valve, and a date that is out of range on a DOT cylinder.
• The regulator and lines. Look for cracked hoses, green corrosion on brass fittings, and any sign of a repair done with tape or the wrong parts.
• The appliances. Ask the seller to demonstrate each one, and watch for a lazy yellow flame or a burner that will not stay lit.
• The alarms. Press the test button on the LP gas detector, the smoke alarm and the carbon monoxide alarm. Check the replacement date on each unit.
• The smell. If you smell propane at any point, stop the inspection and have the system checked by a qualified RV technician before going further.

A leak test is not a do-it-yourself job. It requires a qualified RV technician with the right equipment, and the same applies to regulators, lines and appliance work. Do not accept a seller’s assurance that the system was “just checked” without paperwork.

Refilling and travelling with propane

Refill where a trained attendant dispenses propane, such as a propane supplier or a campground that sells it. The attendant should check the cylinder date and the OPD valve before filling. If a cylinder is out of date or missing its OPD, it should not be refilled.

Travelling with propane on is a common question. The cautious practice is to turn the tank valve off while the RV is moving, unless an appliance such as a refrigerator is designed to run on the road and the system has been checked. If you do travel with the valve open, make sure the refrigerator and furnace are in good order and that nothing is blocking ventilation. Either way, turn propane appliances off before refuelling, and check the route: some tunnels and bridges restrict vehicles carrying propane.

Before any trip, check the tank level and the condition of the pigtail hoses that connect the cylinders to the regulator. A cracked pigtail is a common source of a slow leak.

What to do if you smell propane

If you smell propane inside or outside the RV:

1. Put out all flames, including pilot lights and cigarettes.
2. Do not operate electrical switches, light switches, or appliances.
3. Close the tank valve if it is safe to do so.
4. Open doors and windows and get everyone out.
5. Have the system checked by a qualified RV technician before using it again.

Do not try to find the leak with a match or a flame. Do not use a phone or a switch inside the RV. Once outside, call for help if the smell is strong or you cannot close the valve.

Alarms and detectors

RVs carry smoke, carbon monoxide and LP gas alarms. Test them and replace them by the date on the unit. An LP gas detector near the floor is your first warning of a leak, and a carbon monoxide alarm is your warning that a furnace or generator is producing exhaust gas inside the coach.

A detector that is past its replacement date, or that fails its test, is not protecting you. Replace it before the next trip. If the detector alarms and you cannot find the cause, treat it as a real leak and get out.

What goes wrong: common mistakes and red flags

• Ignoring the date on a DOT cylinder. An out-of-date cylinder should not be refilled until it is requalified, and a seller may not mention it.
• Overfilling. A cylinder filled past about 80 percent has no room for expansion and can vent liquid propane.
• A dead or missing LP detector. A used RV may have a detector that is years past its replacement date.
• Doing your own leak test or repair. Propane work is a job for a qualified RV technician. A home repair on a regulator or line is a red flag.
• Travelling with the valve open and an appliance in poor condition. A refrigerator or furnace that has not been serviced can leak or produce carbon monoxide.
• A gas smell that the seller calls “normal.” It is not. Walk away or make the sale conditional on a technician’s inspection.
• A cylinder with no OPD. Since 2002, 4- to 40-pound cylinders need one to be refilled.

Where propane fits in the rest of your ownership routine

Propane is one system among several. Put the tank, regulator, hoses and alarms on your RV maintenance: a seasonal schedule for a used RV so they are checked before every season, not just when something fails. The 12-volt and 120-volt side of the coach is covered in RV electrical basics: 30 amp vs 50 amp, batteries and generators, and the two systems meet at the appliances, which use 12-volt controls, and at the alarms.

If you are buying a used RV, have the propane system inspected by a qualified RV technician before you sign. If you already own one, test the alarms, check the cylinder dates and look at the hoses before the first trip of the season. When in doubt, turn the valve off and call a technician.