I wonder if having a warmer extra tank would backfill into the main tank because of temperature difference and pressure if both valves were open? Would there be enough to matter?My Class C has a smaller 12 gallon tank that gets used up fairly quickly with the furnace on. Since I installed the extend-a-stay , I try to use a 5 gallon tank to supplement and avoid using the main tank. I have had the main tank closed when using the smaller tank. I would assume that if both were open, the vapor would equalize and condense in the colder tank. Is this a small amount or could I actually add a good amount back into the main tank if it was much colder than the smaller 5 gallon tank?

Nope- it takes liquid flow to really amount to anything. You can fill using a cylinder turned upside down and a double ended POL hose, but even that is slow.

Chris Bryant wrote:Nope- it takes liquid flow to really amount to anything. You can fill using a cylinder turned upside down and a double ended POL hose, but even that is slow.That's what I thought, it would be a slow condensing process. Just a pain to refill the main tank often.What's the double ended POL hose, does that connect to the main tank filler?

I actually refill through the outlet of the tank- I remove the regulator and use the POL there with the double headed hose- just two standard old style pigtails hooked together with an inverted flair coupler.With the cylinder above the tank you can hear the liquid flowing.

Chris Bryant wrote:I actually refill through the outlet of the tank- I remove the regulator and use the POL there with the double headed hose- just two standard old style pigtails hooked together with an inverted flair coupler.With the cylinder above the tank you can hear the liquid flowing.Any photos?Since the Extend-A-Stay is already hooked up, can I just turn the tank up side down and open both valves?The Extend-A stay is between the tank and regulator.

Charts say my 5 gallon tank 80% filled at 70 degrees has a pressure of 95psi and the main tankat 50% at 50 degrees will be 46 psi. 50psi difference. That's vapor but should be the entire tank right?

Can propane Extend-a-stay tank add to main tank?

16 Replies

DAS26miles
Explorer II
Jan 14, 2017
SCVJeff wrote:
If this is for Quartzsite, wait till you get there where its way cheaper

Yes and no. Still not sure. Have half a tank or 5 gallons. Last time there we stopped at the RV Pit stop and it was fast and cheap. I do have a full 5 gallon jug of propane which should get me thru the 4-5 day trip.
SCVJeff are you there or going?
Chum_lee
Explorer
Jan 14, 2017
If you look at most propane refilling stations, the operator first turns on a . . . . pump . . . to transfer liquid propane from one tank (the supply) to another. (the tank to be refilled) If they didn't have the pump you would be there all day!

Chum lee
SCVJeff
Explorer
Jan 14, 2017
If this is for Quartzsite, wait till you get there where its way cheaper
DAS26miles
Explorer II
Jan 14, 2017
MrWizard wrote:
you have to refill the portable tank, regardless

you will be better served, by filling both the rv tank and the portable

shut off the rv tank, use the portable, until empty or darn near
switch to RV tank, go fill the portable, then go back on portable
this will give you the most time on the portable, and the the most time until you have to move the RV for refill

trying to fill the rv from the portable won't work efficiently and you will only shorten the use time on the portable tank, and have to refill it sooner

Excellent point MrWizard. That's basically what I have been doing. I'm just no happy leaving the small tank out over night for thieves to come by and pick up. Yes, I do have it chained to the MH..
MrWizard, where do you hang out these days? I recall you did live just south of me in what was Van Nuys. Not sure what they are calling it these days. We were in Granada Hills, then Sepulveda, North Hills, North Hills West and now back to Granada Hills.
RJsfishin
Explorer
Jan 14, 2017
Chris Bryant wrote:
I actually refill through the outlet of the tank- I remove the regulator and use the POL there with the double headed hose- just two standard old style pigtails hooked together with an inverted flair coupler.

With the cylinder above the tank you can hear the liquid flowing.

I do this same thing now and then to top off at home, and save the hastle of getting a few gallons. If you connect it in the evening while temps are falling, it transfers faster.
MrWizard
Moderator
Jan 13, 2017
you have to refill the portable tank, regardless

you will be better served, by filling both the rv tank and the portable

shut off the rv tank, use the portable, until empty or darn near
switch to RV tank, go fill the portable, then go back on portable
this will give you the most time on the portable, and the the most time until you have to move the RV for refill

trying to fill the rv from the portable won't work efficiently and you will only shorten the use time on the portable tank, and have to refill it sooner
time2roll
Nomad
Jan 13, 2017
If propane did flow due to unequal temperature it would not be much until the evaporation chilled the propane into temperature equilibrium.
DAS26miles
Explorer II
Jan 13, 2017
Isaac-1 wrote:
There is also the danger here of getting liquid propane into the regulator

Good point here. Doing a transfer by temperature/pressure using vapor only will no be feasible. Off to Camping World to refill the propane then.
DrewE
Explorer III
Jan 13, 2017
DAS26miles wrote:
Charts say my 5 gallon tank 80% filled at 70 degrees has a pressure of 95psi and the main tankat 50% at 50 degrees will be 46 psi. 50psi difference. That's vapor but should be the entire tank right?

I'm not sure what the question is here. The pressure is the same everywhere in the tank (well, ignoring mostly theoretical differences due to the flow of gas, which is immaterial here), and that pressure is the vapor pressure of the propane at the temperature in the tank. The difference in pressures is due to the temperature difference only.

Using propane, particularly at a relatively high rate, will cause the temperature in the propane tank to go down as the liquid propane evaporates to become gas.
Isaac-1
Explorer
Jan 13, 2017
There is also the danger here of getting liquid propane into the regulator