Running out of propane (LP gas) unexpectedly when RVing sucks. Pure and simple. One minute your RV furnace is pumping and the cabin is warm and cozy and then poof! the propane runs out and you’re left out in the cold, literally. Or, just as you are cooking up a delicious road meal for the whole family the flame goes out, leaving you with a half-cooked offering that even the dog’s not that keen to eat.
To avoid these kinds of inconveniences you need to know what you can expect from your RVs propane tanks in terms of how long they will last. Generally, propane tanks have 12 year lifetime with a the possibility to get them re-certified after 5 years.
Off the bat from a usage perspective we can offer a very general answer. A gallon of propane burned at the rate of 1,000 BTUs per hour will give you about 95 hours of service. That sounds like a lot right? That’s the problem, when you start doing the math, it’s not. A good RV cooktop, one that allows you to actually COOK rather than just heat things up, usually has a BTU rating of around 30,000 BTUs per hour. So that cuts that 95 hour usage time to around 3.17.
There are other considerations to keep in mind as well, when determining – or trying to determine – how long a propane tank will last. These are all things we are going to cover here, to help you make sure you don’t run out of (propane) gas next time you hit the road or have problems getting it re-filled due to certification issues!
What is Propane Anyway?
Propane is a liquefied form of petroleum gas, often referred to as LPG. It is separated from natural gas, then liquefied and stored inside a tank. It’s colorless, odorless and nontoxic. The smell some people notice is from a chemical called ethyl mercaptan that is added to a propane tank so that if it leaks the rotten egg smell will make sure you know about it.
RVers use propane in lots of ways. It can be used for heating, cooking, setting up a campfire and even as a power source for LP refrigerators so you can keep produce cool when you’re on the move.
RV Propane Tank Types
There are two main types of propane tanks that can be used with an RV: ASME tanks and DOT cylinders.
Both kinds are offered in tank sizes appropriate for RV use with the most popular being 20, 30 or 40 pounds.
You can buy larger tanks, but a 250 or 500 pound tank is not exactly something that is easy to transport.
What's the Difference Between ASME and DOT Tank?
ASME tanks are, as their name suggests, approved by a regulatory body called the American Society of Mechanical Engineers. These tanks are built onto the frame of a motorhome and so, as they cannot be removed need to be refilled in place. They’re generally heavier than a DOT tank of the same capacity. These are for stationary installation. No certification period is required ( but they do need a periodic inspection).
DOT cylinders are regulated according to Department of Transportation rules and as they are designed to be easily replaceable they are mounted in exterior propane tank holders located on the bumper of a trailer. These are the kind of propane tanks you can swap out at a gas station when they are spent. These are designed for portable applications such as those found in recreational vehicles and re-certification is required after 12 years from the date of manufacture and then every 5 years.
How Do I Know How Many Gallons of Propane are Left in the tank?
We know, it’s annoying that propane tanks are rated in pounds when what you really need to know how many gallons of propane they contain. But as tanks are sold in standardized sizes, the amount of propane they hold, when full, are the same as well. As a general rule the following is true:
- A 20 lb tank holds 4.5 gallons
- A 30lb tank holds 7 gallons
- A 40lb tank holds 9.4 gallons
Before you get carried away with the idea that the biggest propane tank is best, you need to remember to take weight into consideration. A 20lb propane tanks does not weigh 20lbs when it is full, it weighs closer to 36 lbs instead. A full 40lb propane tank tips the scales at a whopping 71 lbs and that heavier than some smaller RVs can safely handle, not to mention what it might do to your fuel economy (the heavier your RV is, the more you use.)
A 30lb propane tank – which weighs around 54 lbs when full – is the size chosen most often by frequent RV travellers and they usually supply all the things they need to – furnace, water heater, stove and refrigerator – very well.
How many years does a propane tank last?
RV propane tanks will expire twelve years after the date of manufacture (federal law).
At the 12-year mark, cylinders must be tested and re-qualified, or disposed of.
Portable cylinders such as those used by RV’s have several permanent markings on the top of the cylinder – showing you the “test” or “re-qualification/re-certification” date.
You’ll find that once the expiry date has been reached, you’ll find it pretty challenging getting it refilled without a re-certification stamp.
Here’s a quick way to find out what those markings on your RV propane cylinder means:
- A date without a letter suggests the next re-certification must be done within 12 years.
- The letter “S” following the date denotes the tank must be re-certified within 7 years of the marked date.
- The letter “E” following the date denotes that re-certification is required again within 5 years of the marked date.
- If there is no do date or there is a date past one of the guidelines above, you’ll need to take it to your propane provider and get your cylinder re-certified (if possible) or get a new one.
Now if they are rusted out or otherwise appear damaged, just buy a new one. If not and if it appears to be in good shape, get it re-certified.
Simply drop off the expired propane tank at a local propane outfit for recycling.
How Long Do RV Propane Tanks Last?
That, of course, is the big question. There are so many variables. Are you going to be using the furnace? How many showers are you and your fellow travellers going to take that call for hot water? How often are you going to cook? These things affect how long your propane tank will last before it needs a refill, along with the actual fuel consumption of the devices it is powering themselves.
There are actual mathematical equations you can use to do this, but if you don’t feel up to geeking out quite that much there are also online calculators and a number of apps you can download for your smartphone that do the hard work for you. They let you enter the tank size, the BTU of the appliances you will be using and they then calculate the approximate burn time you can expect. It’s only a best guesstimate, but it will help you figure out how far you go without needing to make a refilling pit-stop.
Or, you can make life even easier an opt for a propane tank usage gauger. These are becoming more and more common and is something that RVers can rely on for increased accuracy.
So what do you do when it’s time to re-certify your RV propane tank?
Propane cylinders are subject to recertification (also know as requalification) 12 from date of manufacture and every 5 years thereafter. For instance, a cylinder manufactured in March of 2018 will have to be re-certified in March of 2030.
Over its lifetime your RV propane cylinder may be exposed to any number of corrosive elements, it may be dented or the valves may begin to leak or malfunction – deeming it dangerous.
The visual inspection that occurs during re-certification will identify these potential safety concerns so that it will continue to operate safely.
If you have worked out that your cylinder is due for re-certification or a propane place has notified you that your cylinder is out of cert – get it re-certified.
It can cost as little as $10/tank to get re-certified and completed in about 10 minutes.
To find a place to get your camper or RV propane tank re-certified, just google “propane tank certification” followed by your city and state or your zip code and that should yield lots of choices and locations for you. Do note that prices for re-certification vary widely by region and/or dealer.
Does Propane Expire or Go Bad Over Time?
No, contrary to popular myth, propane does not expire or go bad. As it is stored in a sealed tank, nothing can come in contact with it to cause it to do so. The exception is – and it’s the source of the much repeated myth that propane expires – if your horizontal or vertical propane tank is damaged and does expose the gas inside to the elements then you will have a problem.
So, keeping your propane tanks in great shape is a must, but provided you do that then your propane will last for a long time.