Hi, one of the biggest issues I have RVing is after filling/changing my lp tanks is getting appliances to light! I believe the issue is air in the lines.How can this be prevented?Don't the regulators have a built-in check value? Or should I put a shut off ball valve next or near the tank(s).Your experiences would be appreciated.Thanks Bob

There are no check valves in there that I'm aware of . I purge the air thru the stovetop burners and once they light and burn for a minute everything seems to be ok. Can't imagine extra ball valves helping because there will be air between the valve and tank fitting when the tank is hooked back up

You can't prevent it. Just light the burners on the stove first and let it flush out the propane lines. A minute or two of them burning is sufficient.

My only problem is with the refrigerator after the unit has been in storage. My refrigerator is near the furnace, so I first turn on the furnace. After it ignites, the refrigerator will work on gas.

After picking up the trailer at the storage yard I'll open the valve on the propane tank and light one of the burners on the stove top to purge the air from the LP line. Once one of the burners stays lit I'll turn it off and then light the pilot on the refrigerator. You'd think that between the valve on the tank and the control knob on the stove top that the system would hold gas and not let air in but it doesn't. I've come to accept that that is just the nature of the beast.

Do not disconnect tanks any longer than needed, And do one tank at a time, not both. I grew up with propane. We had like 5 100 pounders outside our kitchen window.. (might have been six) these provided hot water and kitchen stove.. NEVER did we have to re-light the water heater,, NOT once. Later we used Propane to heat other buildings, plus there was a 2nd house that used propane for cooking and hot water. Never had to relight a pilot due to air in the line. Never. Not in the roughly 20 years we lived there.. Oh we did have to relight from time to time, but that was when we accidently ran COMPLETLY out of gas and had to haul a bottle to a refill station till the delivery man came by with new tanks.. (He was an "On Call" Service, nto a "Same day every month" service).Finally I will add that pilots are hard to re-light, this is on purpose. It is a safety issue. You have to hold the override button, while lighting the pilot, then continue to hold it for a good minute in most cases. sometimes longer. On some of the pilots I deal with even today (oven) that may not be enough.. Takes time for the pilot to heat the thermocouple so it generates enough CURRENT (not voltage) to get the magnet to hold the valve open.

Air in LP gas line. | Good Sam Community

wa8yxm
Explorer III
Feb 20, 2016
Thomas/NH wrote:
As a licensed gas technician, the gas doesn't drain out. You don't need to purge the line. It's a matter of pressure and once it restored, the appliance will light right back up. What small amount of air that you let in during change-over will be absorbed and pass through the burner as a yellow flame.

Slowly turn the tank valve back on so you don't stick the regulator.

THANK YOU.. (I said as much about the gas lines up thread but unlike you I'm not certified in this field. so Thanks for the professional support).

Question.. The pigtail that connects to the tank, does it contain a check valve or other valve.> Else I would think that Browian motion of the gas and air would let a little air enter, Not, likely, enough to make a difference, but there would be some exchange.. I know there are check valves farther in but as I said, in around 20 years of growing up with Propane.. I never had to re-light a water heater due to a bottle change less we ran out completly. And then it was the standard pain in the arse to re-light as if I'd turned it off at the control.
time2roll
Nomad
Feb 19, 2016
Had similar issue when stored for a bit. I believe the regulator was leaking.
New Cavagna regulator and no issues. Everything fires right up.

Never had the issue when refilling propane on the road.
Old-Biscuit
Explorer III
Feb 19, 2016
coolbreeze01 wrote:
rhagfo wrote:
coolbreeze01 wrote:
I make sure the unit is well vented and turn all the stove burners on until I'm sure there is raw gas and turn them off. I let the gas dissipate and then light a burner.

:S :S :S

Really Bad Idea and method!!! If having issues Light a burner, use a match or butane match stick to light the burner.

The amount of time has little to do with air in the line, While operating on the second tank, I have pulled the 1st and gone to work and had it filled on the way home, hooked up once back at the trailer. Then slowly opened the valve once hooked up.

Its worked for 40 years for me but might not be a good idea for those that can't smell or recognize propane fumes :R
coolbreeze01
Explorer
Feb 19, 2016
rhagfo wrote:
coolbreeze01 wrote:
I make sure the unit is well vented and turn all the stove burners on until I'm sure there is raw gas and turn them off. I let the gas dissipate and then light a burner.

:S :S :S

Really Bad Idea and method!!! If having issues Light a burner, use a match or butane match stick to light the burner.

The amount of time has little to do with air in the line, While operating on the second tank, I have pulled the 1st and gone to work and had it filled on the way home, hooked up once back at the trailer. Then slowly opened the valve once hooked up.

Its worked for 40 years for me but might not be a good idea for those that can't smell or recognize propane fumes :R
CavemanCharlie
Explorer III
Feb 19, 2016
After I installed a new regulator on the stove in my TT I no longer have any problems nor do I have to wait for the gas to get to the stove. It lights right up after I change tanks with no hesitation. The fridge lights automatically and will relight itself . I do have to relight the pilot on the water heater but, it is closest to the tank. It relights right away.

But, I do switch the tanks out within a few minutes and don't let the line set empty for very long.
Thomas_NH
Explorer
Feb 19, 2016
When I read theses responses I just sit here and chuckle to myself. The thought that comes to mind is that old saying: "Go Modern, Go gas, Go Boom... Where do you think the gas goes when you disconnect the tank? Does it drain out of the pipes? How does all that air get back into the piping?

As a licensed gas technician, the gas doesn't drain out. You don't need to purge the line. It's a matter of pressure and once it restored, the appliance will light right back up. What small amount of air that you let in during change-over will be absorbed and pass through the burner as a yellow flame.

Slowly turn the tank valve back on so you don't stick the regulator.
Old-Biscuit
Explorer III
Feb 19, 2016
Don't run out of propane.....

It isn't so much as 'air' in system.

It is more about establishing flow and placing a demand on regulator.

The system when fully pressurized is only 0.4 psi (11" WC)

With no demand the regulator is basically closed. Turn on an appliance and depending on it's demand will determine how quickly flow can be established based on that demand (fridge 2000btu---stove top 6000/9000btu per burner----water heater 10,000btu----furnace 35,000btu)

Such is the life of a small lp system and the way RV lp system is used.
ewarnerusa
Nomad
Feb 19, 2016
I have found the trick is to just make sure you open the gas valve at the tank very slowly. Like 10-15 seconds for the initial quarter turn. After that, just crank it the rest of the way open without regard to speed. Something about that initial slow opening seems to purge the lines properly and I'll often find that gas is immediately available at the stove/fridge/furnace/WH. If I don't do the slow open, it is usually a several minute process of trying to purge at the stove top, having limited success, going back out and closing and reopening the tank valve, repeat the process...
rhagfo
Explorer III
Feb 19, 2016
coolbreeze01 wrote:
I make sure the unit is well vented and turn all the stove burners on until I'm sure there is raw gas and turn them off. I let the gas dissipate and then light a burner.

:S :S :S

Really Bad Idea and method!!! If having issues Light a burner, use a match or butane match stick to light the burner.

The amount of time has little to do with air in the line, While operating on the second tank, I have pulled the 1st and gone to work and had it filled on the way home, hooked up once back at the trailer. Then slowly opened the valve once hooked up.
RoyB
Explorer II
Feb 19, 2016
We use the stove burners here as well... No big deal for us...

Roy Ken

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