Thread Tools Search this Thread Display Modes
Old 09-14-2010, 04:58 PM   #1
3 Rivet Member
BessieB's Avatar

1997 21' Excella
Carson City , Nevada
Join Date: Jun 2009
Posts: 174
Images: 6
doesn't all gas get sucked out?

My husband just returned from filling the tanks. I don't think our regulator works cause while I was out, I had to manually switch the tanks when my water heater wouldn't ignite and my refer was trying to fire up and couldn't. So manually switched the tank. Fired right up. When hubby got home he said the tank wasn't completely empty. Sooooooooooooo, my question, is it common that when the gas gets to a certain level that the appliances can't suck up that gas?
Thanx all brilliant ones.
PS We also will have to update our tanks also.

BessieB is offline   Reply With Quote
Old 09-14-2010, 05:40 PM   #2
jcanavera's Avatar

2004 30' Classic Slideout
Fenton , Missouri
Join Date: Mar 2002
Posts: 9,048
Images: 143
Send a message via AIM to jcanavera Send a message via Skype™ to jcanavera
Your appliances received gas which is fed by pressure. The liquid propane turns to a gas at the upper reaches of the tank. The regulator keeps too much pressure from feeding into the gas lines. Once the liquid falls below a certain level, the remaining liquid gas that is vaporized falls too low to maintain a flame on the appliance. If both tanks have their valves open, the regulator should sense the low pressure situation in the near empty tank and switch over to the full tank. That's assuming you have a properly functioning two way valve and again, you have valves open on each tank. Assuming the valves were open and you could not support a flame, my guess is that your regulator might be defective.


Jack Canavera
AIR #56
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700
jcanavera is offline   Reply With Quote
Old 09-14-2010, 05:53 PM   #3
Rivet Master
Wingeezer's Avatar
2005 30' Classic
Burlington , Ontario
Join Date: Sep 2008
Posts: 2,740
Well, for what its worth here's my take! I'm sure there are folks here that know more about propane that I and hopefully they will comment.

Firstly, propane in your tank is stored in liquid form. There is space at the top of the tank and some of the liquid evaporates to fill the space with gaseous propane - it develops a pressure called the "Vapour pressure" and that pressure is dependent on whatever the ambient temperature is.

So your appliances don't "suck" the gas out, it is forced out by the pressure in the tank. As gas is removed, more will "boil" off the liquid propane in an attempt to reach the vapour pressure, and that gas will continue to operate your appliances.

The pressure in your tank is much higher than in your lines - as i said, it depends on the ambient temperature but can easily be over 100 psi.

The purpose of the regulator is to reduce the pressure to a much lower level - less than one psi - to feed the distribution system and appliances in your trailer.

As long as there is any amount of liquid propane left in your tanks, this situation remains the same and your appliances should work.

The vapour pressure in the tank should be the same with a tank that is full or, lets say, three quarters empty.

Once the liquid propane has all boiled off to become vapour, pressure will drop quickly in the tank as you draw the remaining gas off.

It is at this point that the automatic changeover valve should flip over and start drawing from the second bottle - as long as you have the bottle valve open on the second bottle!!

I'm assuming that you did have both bottles open at the outset and didn't just get things going again by opening a full bottle that was connected but left with its valve closed!

As far as I always understood, all that the manual flipper does is to reset the sight glass indicator from red back to white, and point to whichever bottle is providing gas so you know which one needs refilling.

Perhaps it is possible that if an auto changeover valve is defective - manually flipping the lever will cause the auto valve to change over even if it is defective and won't change on its own. If so, i was not aware of that feature.

Maybe I am missing something and someone who knows more will comment and I will learn something too!

Brian & Connie Mitchell

2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.
Wingeezer is offline   Reply With Quote
Old 09-14-2010, 06:00 PM   #4
3 Rivet Member
BessieB's Avatar

1997 21' Excella
Carson City , Nevada
Join Date: Jun 2009
Posts: 174
Images: 6
We figger we need a new regulator anyway. It hasn't switched before in the middle of use on our real cold outing.
BessieB is offline   Reply With Quote
Old 09-14-2010, 07:53 PM   #5
2 Rivet Member
Currently Looking...
St Cloud , Minnesota
Join Date: Jan 2009
Posts: 28
In my experience the regulator and tanks don't always perform according to theory. They can test out fine in the shop and occasionally fail to perform in the field - even when new.
JamieEllis is offline   Reply With Quote
Old 09-14-2010, 08:35 PM   #6
1972 Travelux Princess 25
Cobourg , Ontario
Join Date: Oct 2008
Posts: 1,042
The boiling point of Butane is .5 degrees Celsius, right around the freezing point. The boiling point of Propane is much colder, -51C.

LPG or liquid petroleum gas, is a mixture of the two. If there was a lot of butane in the mix perhaps it wasn't vaporizing very well due to the cold, resulting in low pressure?

They use more butane in the mix in hotter climates in the summer. If you last got the tank filled in the summer, especially if it was in Texas or Arizona or New Mexico maybe it had too much butane to vaporize in freezing weather.

To test this theory you could try the tank again on a warm sunny day or pour some hot water over it.

It's also worth keeping in mind that as the gas evaporates it chills the tank. So the more you use the colder it gets. This could have the effect of dropping the temp below the boiling point, if it was already cold and had a lot of butane in it.

If the weather is getting cold your LPG supplier should have changed over to a more propane rich mixture. Get the tank filled and it should be fine from now on.
Living in the trailer park of sense, looking out the window at a tornado of stupidity.
Ganaraska is offline   Reply With Quote
Old 09-14-2010, 09:09 PM   #7
Rivet Master
NevadaGeo's Avatar
1978 31' Excella 500
Genoa , Nevada
Join Date: Jul 2007
Posts: 1,318
Hey neighbor! Maybe your tank was just almost not quite completely empty. Do you go over to the Silver City RV? They're pretty nice folks there.
Hey plan on coming down to the Genoa Candy Dance fair the 25-26. If you're bored tomorrow, they're still making some candy in the town kitchen and love all the volunteers that show up, I hope to get over there in the afternoon or evening.
I admit to being powerless over housecleaning and social niceities
Airforums 22655 and now, WBCCI 22655

NevadaGeo is offline   Reply With Quote
Old 09-15-2010, 04:08 AM   #8
Rivet Master
AIR-Quarius's Avatar
1970 27' Overlander
Espanola , Full Timer
Join Date: Jun 2007
Posts: 1,752
Images: 39
Send a message via Yahoo to AIR-Quarius Send a message via Skype™ to AIR-Quarius
Sometimes , but not often ours (regulator) has somehow stuck and we have tapped on it with the handle of a screww driver. When the propane runs out, you can smell it, as far as going on when you think it has run out.
AIR-Quarius is offline   Reply With Quote
Old 09-15-2010, 04:52 AM   #9
Rivet Master
r carl's Avatar
Vintage Kin Owner
Lin , Ne
Join Date: Dec 2009
Posts: 2,138
If your regulator is 20yrs old I would replace it. I replaced my $49 automatic switchover Marshall 205 and put on the optional $1.50 cover, works great and gave me peace of mind.

r carl is online now   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
What fitting for GAS on Atwood gas/elec WH rlindberg Water Heaters, Filters & Pumps 1 04-09-2010 11:29 PM
Need pictures of gas line for Magic Chief oven gas connection dghaas General Repair Forum 1 01-30-2009 09:04 PM
Gas or No Gas, that's the question... oldtrucksrul LP Gas, Piping, Tanks & Regulators 14 11-16-2008 10:29 AM
Locking Gas Cap for 2003 AS Gas Motorhome spat61 Land Yacht/Legacy Motorhomes 11 10-27-2008 11:37 AM
Getting sucked in - Stablizer bars or not? FordTruck Hitches, Couplers & Balls 14 09-16-2006 10:09 PM

Featured Campgrounds

Reviews provided by

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 06:54 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.