Air in LP gas line.

[WNYBob]

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

[wa8yxm]

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]

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]

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]

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]

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]

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]

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]

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]

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]

We use the stove burners here as well... No big deal for us...

Roy Ken

[WNYBob]

I've been using the burners also, I was hoping that someone had a better idea.

Thanks for the replies.

[coolbreeze01]

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.

[Sam_Spade]

Just the nature of the beast.

I do stove burners first, then water heater for a couple of minutes, then propane furnace.....by then, the fridge takes care of itself.

Thankfully I have electronic igniters on everything.....but I use a "grill lighter" for the burners.

[tonymull]

Yes, just one at a time with gas still flowing from the 2nd tank. Fill one, reinstall it, turn it on, switch to that tank, then fill the other one. The most annoying thing is the refrigerator as the propane seems to only move about half an inch with each attempted relight 😉 But my refrig is 18 years old, so maybe it's easier nowadays.