LP Gas – A Short Course

By Gary Motley

Master Certified RV Technician

The LP (Liquified Petroleum) Gas system is one of the most important systems in a recreational vehicle. It is also one of the least understood. This system is safe when maintained and used properly. However it can cause some big bangs when not properly used or maintained. As a result of talking to customers about their LP Gas systems over the years, I have become aware of a number of items I feel is important for consumer to know. I am going to cover some of these items in this article.

When opening our LP tank valve, you should open it very slowly. This will help prevent a surge of pressure into the regulator, which can blow out the diaphragm. You should also listen for a constant loud hiss or hum at the regulator after opening it as this is an easy way to detect a major leak. When opening this valve, you should open it all the way to the top. This will help the o-ring seat off the valve properly to avoid a possible leak.

You should check all the tank and line connections periodically to be sure they are tight. When testing for leaks, liquid leak detector solution should be used. Do not use liquid soap as ammonia or chlorine in the liquid soap can damage the brass fittings. You should never use a match to look for leaks!

On dual tank installations where the tanks are mounted on the tongue, you should turn the tanks so the guard faces forward to help protect the valve and hoses from debris. This should also be a consideration for the mounting location of the regulator.

When tightening the POL nut (left hand thread), you should use a proper size wrench and draw it up only real snug. No pipe dope or tape is needed as this is a machined brass fitting to make the seal. You should also turn on the valves and check the connections for leaks with the proper solution any time the bottles have been disconnected.

The regulator is pretty much the heart of the LP system. There are a few things of interest and importance about the regulator that your should know. The regulator should put out a pressure of 11" water column. This is equivalent to 6.25 ounces per square inch (of pressure). The regulator is adjustable and can be adjusted by a competent RV technician with the proper type of gauge. You should be certain that the gauge being used has been calibrated properly within the last month. This is very important as incorrect pressures can cause major problems with the performance of LP appliances.

A regulator can vibrate while traveling and work its way out of adjustment. This is the main reason it needs adjustment. A regulator properly adjusted should operate at 11" water column while half the potential load is on the system. It is also a good ideal to have the technician do a lock up pressure test on your regulator. This will assure the regulator is shutting properly. A drop pressure test at 8" water column for 5 minutes is how you would make certain you have no leaks in your LPG system. To do this, you pressurize the system and close the gas valve(s). Then with the manometer hooked up. You drop the pressure (usually through a stove top burner valve) to 8" water column. After lowering to 8", you should let everything set for five minutes. Any drop from 8" would indicate that gas is escaping. This could create a big bang. A rise from 8" would indicate the valve on the tank is not closing completely. A very slight rise is acceptable as this would simply be expansion due to heat.

Regulators have a vent on them. This vent should be pointed within 45 degrees of straight down. This will prevent water and debris from getting in and causing problems. All regulators should have a cover if they are not in a LPG compartment which should be vented. This is according to RVIA code as is the 45 degrees thing.

A few more statements of importance about LP gas:

1. High altitudes and low temperatures can have an adverse effect on the performance of LP gas. One of the best ways to help alleviate this is to keep your tank(s) full in either of these situations.
2. LPG detectors can be set off by a number of things besides just LP gas. Some of these include:

• Low battery voltage in the coach.
• Hair sprays, deodorants and other aerosols.
• Glues, perfumes, lacquer, gasoline and even alcoholic beverages

    4.  You should never, under any circumstances, unhook the LPG detector. No more discussion.

    5.  A gallon of LPG has approximately 91,000 BTUs of heat. The amount of BTUs consumed by RV appliances is normally as follows:

• Heater, 12 to 45K per hour.                          
• Water heater, 8500 to 12k per hour.              
• Oven, 7100 per hour.                                                                           
• Refrigerator, 1000 to 2000 per hour                

     7.  You should use a POL plug when transporting LPG cylinders. Don't transport them inside the passenger compartment of your vehicle.