How Low Can I Safely Let a Propane Tank Get?

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Often due to our busy schedules, there is no time to monitor gas levels. And before you realize it, your gas is finished. But did you know having your propane tank run out is hazardous

Regulations require that propane be used only to a certain level before refilling. You have probably heard that you should not let your propane tank below 20 percent. Why is that so? This is what we are discussing today. 
You will learn how propane systems work, ideal propane tank level rules, why the magical 20% rule is important, and the consequences of not following the rule. We’ve got a lot to cover. Let us dive in!

How Propane Systems Work

Propane gas is delivered from the vendors’ tanks in pressurized form and stored in a sturdy tank. You are probably familiar with the common propane storage tanks; propane cylinders, garage heaters, and backyard, or underground tank types

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Propane changes to the vapor form as it flows into a network of pipes on its way to your appliances. Whether you are using the grill, furnace, cooker, or fireplace, these appliances will not only use propane in vapor form.

Naturally, propane is a colorless, non-toxic, and odorless gas. Odorless? Yes, that is true. We know you are used to the odor-producing propane gas form. But that is because of a compound added for detecting leaks or spillage.
Note also that, when mixed with oxygen, propane is a highly flammable substance. Therefore, take precautions to avoid fire hazards. Always install propane tanks outdoors, following the laid procedure, including adequate ventilation.

Understanding Propane Tank Levels

There are two notable percentages regarding propane tanks: 80% and 20% levels. The conventional requirement is not to allow a propane tank below 20 percent before refilling. We will elaborate more on this later in this article. 

But first, let us understand the 80% bit. You must have noticed the gauge of a newly refilled tank reads only 80% full. This is done on purpose. Propane is a heat-sensitive gas with a high tendency to expand in hot weather.

That is why space is required to allow for expansion with the rise in temperature by filling only 80% of the tank. It is a safeguard to protect the tank from bursting.
For illustration purposes, a 500-gallon tank is filled only with 400 gallons of propane, equivalent to 80%. The rest of the space, approximately 100 gallons in capacity, caters to the expansion of the gas in the tank.

Why 20%?

The 20% determines how low can propane tank go. At a propane tank below 20 percent, you lose the safety level gap required in your propane gas tank system. Plus, the lower the level, the harder it is for the tank to provide sufficient vapor to sustain appliances. 

Nonetheless, the system is designed to trigger an alert mechanism when propane goes below the 20% level. Below this level, it will emit an unmistakable ‘rotten eggs’ smell, a reminder to replenish your tank.

Here are some of the potential hazards of failing to observe this rule.

The Heating Systems Switch Off

Obviously, your heating appliances will not work. In case of sudden weather changes, your home is at risk of low-temperature hazards. Pipes may freeze or burst, and family members may get ill alongside other eventualities.

Rusting Tanks and Accessories

Propane creates an insulating coat inside the propane tank and the accessories. Once the gas runs out, the insulation ability is lost. Consequently, the tank’s structural integrity is compromised, which is a propane tank empty danger. Here’s an article showing you how to tell if a propane tank is expired.

Fire Hazards

Gas delivery lines release the residue gas, as valves are often left open when propane runs out. The residue gas buildup can result in fires if accidentally ignited.

Pilot Goes Out

Another problem is the possibility of the pilot light getting switched off. This means you will require a technician to reignite it again. In addition, the propane system will also require testing for gas leaks before refilling. That is an extra cost you would want to avoid.

What Do I Do if the Gas Falls Below That?

Even with the best monitoring, you might find your tank at a 20% level. What to do now?

Do not fret. First, as mentioned earlier, know that if you let the propane tank below 20 percent, you will require a safety inspection. That has to be done by a certified technician to rule out potential leaks.

But there are a few interventions you can take to prevent the possibility of propane running out completely.

Arrange for a Refill

To avoid entirely draining the tank, make an order immediately. The great thing is some dealers even offer enrollment for a delivery program. The program works by installing a monitoring device on the tank and relaying the information via a desktop or mobile app. It’s one of the factors that helps you determine the service quality of your propane delivery company.

That way, they can track your gas usage and send you a reminder for a timely delivery. It is a paid service, meaning additional costs, but the benefits outweigh the consequences of running out of gas.

Reduce the Consumption Rate

How low can propane tank go depends on the type and the number of appliances connected. You want to reduce consumption by turning off some appliances or applying low-consumption settings to others. A good example is lowering the thermostat to a lower temperature output setting.

Keep the Pilot Light On

If the gas level goes too low, the pilot light goes out. Avoid this level, or else you will require costly technical processes before re-ignition.

Use Alternative Fuel Sources

Do you have alternative heating methods you can use? Instead of propane for your heating appliances, in the meantime, appliances, you can opt for wood, coal, or even an electric water heater. Just ensure sufficient ventilation due to the risk of carbon monoxide poisoning.

Final Thoughts

As mentioned above, a minimum of 20% is the recommended propane tank level. Having a propane tank below 20 percent can result in several problems. And this is something you want to avoid. Next time, make sure to re-order before it hits this level. 

As you wait for the new supply, you can take several measures we identified above. In summary, maintaining this routine determines how low can propane tank go. This, in turn, goes a long way in safely enjoying the use of your propane gas system.

Keep Exploring the Content

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Ryan McCabe

Ryan McCabe

Ryan is a home and small business energy expert, having overseen retail propane, heating oil, and HVAC services companies. On ComparePropane, Ryan writes about things that people should know when shopping for or using propane in their homes and businesses. 

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