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Propane tank filling


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Guest Ray Davis
26 minutes ago, MHRookie said:

I’m looking for some clarity.... is it true that some states propane delivery companies cannot fill tanks installed in RV’s.  Is the only option to visit a propane filling center?

Actually IMHO it's a bigger question than a state issue.   A state or city could have their laws, and a park or the gas company might have their own rules.

Each rv park can probably answer the question about their location.  

For someone like myself I never think about propane because we only use it for cooking and a lot of that is electric using microwave, toaster, and induction.                  We have had this rv  over 10yrs and have never bought propane and we still are 1/2 full.

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5 minutes ago, Ray Davis said:

Actually IMHO it's a bigger question than a state issue.   A state or city could have their laws, and a park or the gas company might have their own rules.

Each rv park can probably answer the question about their location.  

For someone like myself I never think about propane because we only use it for cooking and a lot of that is electric using microwave, toaster, and induction.                  We have had this rv  over 10yrs and have never bought propane and we still are 1/2 full.

Same here Ray

And what I love about my diesel fired aquahot and heated tile floors. 

 

I fillef the propane tank 1 time at a

farmers co op.

 

$14.00 

 

 

 

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In South Carolina, the propane supplier needs to have insurance covering rv tank filling when the tank is in/on vehicle.  If the tank is removed, anyone can fill it.  Places that have the insurance charge 30%+ more per gallon.  I have been told of the insurance by multiple suppliers, but only their word as proof.

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The only issue I've experienced is many mobile home parks will not allow propane delivered to RVs. I assumed it was an insurance issue not RV related. I've only filled mine twice in 10 years and it was done by the RV park we stayed in....Dennis

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I have never had to fill outside my home area so can't comment, but I do sometimes give mine a little shot from a "Drug Store RV bottle". I had a local propane supplier make up a hose that lets me transfer from a small tank to my RV. Cost less than $50 as I remember and very handy to have when dry camping.

 

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Guest Ray Davis
9 hours ago, Harvey Babb said:

I have never had to fill outside my home area so can't comment, but I do sometimes give mine a little shot from a "Drug Store RV bottle". I had a local propane supplier make up a hose that lets me transfer from a small tank to my RV. Cost less than $50 as I remember and very handy to have when dry camping.

 

 Harvey,  Your post is very interesting,  I've seen others ask if that was possible and don't remember anyone having actually done it.    I'm curious what you mean by            " Drug Store RV Bottle ".    More details and pictures if possible of your setup would be nice.

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Ray, there were devices that allowed the transfer from one bottle to another. They were unreliable and basically unsafe in the wrong hands. I had one and never could get it to work. That may mean I have the wrong hands. 😆 Regardless, I believe they a no longer made due to legal issues. I'll see if I can find the write up.......Dennis

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Never have had an issue with tank refill. Maybe it’s an east coast thing. Coming up on 4 months stay and still around 2/3 full. Where I’m at the community (55 and older) homes are all classified as RV’s and only have to deal with DMV and most have propane tanks. Nice community but summers of 120 degrees +, no thankyou. 

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Guest Ray Davis
5 hours ago, Dennis H said:

Ray, there were devices that allowed the transfer from one bottle to another. They were unreliable and basically unsafe in the wrong hands. I had one and never could get it to work. That may mean I have the wrong hands. 😆 Regardless, I believe they a no longer made due to legal issues. I'll see if I can find the write up.......Dennis

 Dennis,       I have seen the little coupler devices to recharge those little hand sized bottles.    Is that what you're referring to?   Maybe that's the Drug Store bottle         Harvey mentioned.    The problem with bottle to bottle is as soon as the pressure equalizes the flow stops,   You can apply heat to the full bottle and ice to the empty       one and increase the amount somewhat,  but unless you use quite a lot of the little propane tanks it's not hardly worth the effort.

 Old time refrigeration repairmen I have known would evacuate a system on a hot day by putting an empty Freon container into a tub of ice & water and it would suck       the Freon right out.  Probably wouldn't allow that today,  if they knew about it.   Now don't any of you guys try this at home ........  LOL

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It's been a few years now but when I saw the propane truck in the street filling a neighbor's residential tank in a residential neighborhood, I asked the driver to top off the tank in my MH.  The tank connection is the same.  I was told he couldn't do it.  He said he was not permitted to fill tanks on RVs.  I called the office seeking a waiver - no dice.  It sounded like a different license was required or some legal reason why I was turned down.  I live in St Louis County, Missouri.  To me, it looks like the same truck filling tanks around the campgrounds I visit.  As long as I've got electrical hook-ups, I only need to top off the tank once a year so it's no big deal.

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I live in E TN.

Last time I had my home tank filled I asked the driver if could fill my RV tank if I needed it.  He said yes.  But he also said that he had to do it at the same time as the tank fill and he only a ~2 minute limit to rehook and fill the tank as an automatic safety timer will shut off the pump and he can't restart it again (I assume he could but it would be a pain in the butt that he'd rather not deal with, probably paper work involved). 

The problem with this that the truck delivers on a random basis twice per year, late fall and then early in the year, and I don't know whey it would be here.  If I were here I'd have to get the door open to the garage and door to the propane compartment open, it would be a race to get this done in the time limit.  But next time he is here I'd be willing to try.

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On 3/23/2021 at 8:06 AM, Ray Davis said:

 Harvey,  Your post is very interesting,  I've seen others ask if that was possible and don't remember anyone having actually done it.    I'm curious what you mean by            " Drug Store RV Bottle ".    More details and pictures if possible of your setup would be nice.

Ray, I was referring to the ubiquitous 20 lb. capacity tanks used for gas grills. I honestly dont know how "RV" got tacked on there. My "setup" is just a high pressure hose with a fitting on one end that matches the fill fitting of the RV and a fitting on the other end that matches the portable tank.

After careful reflection I don't think I'm willing to post the procedure for making the transfer. Instead I'll tell you all the reasons you SHOULDN'T do it. Propane in the tank is a FLAMMABLE liquified gas under high pressure . If the fittings are undone with liquid in the hose the liquid will rush out under high pressure and instantly become cold enough to cause frostbite. If the liquid splashes on to clothing or porous gloves it can hold the subzero temperature long enough to cause serious injury. In order to create a pressure differential to move liquid from one tank to the other the bleeder valve on the destination tank has to be partially opened to allow FLAMMABLE gas to escape. The operator must stay close enough and be confident enough to quickly reach into a flame and close the bleeder if the gas ignites to prevent a major fire. 

If you feel like you are ok with all the above I will offer one observation: portable tanks do not deliver liquid if standing upright and some have a float valve inside that shuts off flow if quickly inverted.

I learned how to handle propane as a young man, filling propane fueled tractors on the farm.  The operation was learned by watching it done, with a few words of caution thrown in, and was practised enough to become second nature. Thinking about telling an unknown stranger how to do it gives me pause.

Edited by Harvey Babb
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A common misconception about propane tanks (and aerosol paint "rattle-cans") is that the liquid is injected into the container and then enough gaseous vapor is pumped in to provide the "pressure" to expel the liquid until the container is empty.  Propane is "liquified petroleum gas--LPG".  Liquid propane cannot exist AS A LIQUID at atmospheric pressure, even if the temps are near 0*F--it will "flash off" just as Freon will at atmospheric pressure.  The pressure in an LP gas tank varies with temperature, but at temps you might normally encounter, is in the range of 140-180 PSI.  The liquid propane is not "injected" into the tank and then some gaseous compressor raises the pressure in the tank to some acceptable level.  The pressure in the tank is due to the "vapor pressure" of the liquid propane.  The vapor pressure is the pressure that will keep the gaseous propane in a liquid form at any given temperature.

It may be a difficult concept to understand, but if you were able to "pour" a small amount of liquid propane into a large container (not possible) and then cap it, the pressure inside the container would rise to the vapor pressure of the liquid propane at that given temperature (as long as any propane in liquid form still existed).  If you were then able to "pour" more liquid propane into that container without letting any pressure escape, the pressure in the container would not rise...it would remain the same.  No matter whether a 50 gallon container has 2 gallons of liquid propane or 40 gallons of liquid propane, the internal pressure of the tank will remain the same.  That is why you cannot gage how much propane remains in a tank by checking the pressure.  The pressure is the same when it is totally full as when there is only a small amount of liquid propane left.  The internal pressure is not the result of any gaseous fluid that has been PUMPED into the tank...it is the pressure resulting from the liquid inside wanting to evaporate until it reaches the pressure at which it can no longer evaporate, and must remain as a liquid.

Perhaps to make this easier to understand, consider the propane tank that I filled my forklift tanks at my business.  Our forklift tanks were about 5 gallon capacity.  We filled them from a 250 gallon tank ON STILTS in our parking lot.  We did not need a pump, as you might see when you have a grill tank refilled at a propane retailer.  Why?  Because the pressure in our 250 gallon tank (nearly full or nearly empty) was the same as in our (nearly full or nearly empty) 5 gallon) forklift tanks.  We would just hook up the large diameter hose from the 250 gallon tank to the fitting on the 5 gallon forklift tank.  The forklift tank is marked as to what it should weigh when 80% full (legal limit).  You would place the forklift tank on weight scales, open the valve on the forklift tank, open the 250 gallon tank valve, and the liquid propane would flow by GRAVITY into the 5 gallon tank.  All the while, the pressure in BOTH the 250 gallon tank and the 5 gallon tank are EQUAL.  GRAVITY lets the liquid propane flow from the higher tank to the lower one.  So, you might ask, why does the propane dealer always "pump" the propane into your tank?  Because it is much faster than waiting for the slow flow of gravity, or in some cases, because the propane dealer's tank is below the platform at which he is dispensing, so gravity fill won't work.

Perhaps now you understand why you cannot dispense propane from a 20# tank SITTING BELOW your RV tank, no matter how you connect them.  The pressures in both tanks are equal, and you can't get the liquid propane to "run uphill".  On the other hand, if you held the 20# tank ABOVE your RV tank, and got the SIPHON action going, you could slowly transfer the liquid from your 20# tank to your RV tank.

I tried to make this as simple as possible.  I hope it's understandable.  Most mechanical engineers understand it without question, but it's sometimes hard to grasp for "normal" folks.  😁

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Hi Van,

I'll humbly correct you on a couple of points: Yes you CAN pour liquid propane at atmospheric pressure, and you CAN fill a tank that is higher than the source. On the farm we regularly filled the tractor tanks, above eye level for my 6 foot 1 inch height, from a tank barely 2 feet off the ground, and could transfer the 40 gallons to the tractor in about 3-5 minutes. The key is the bleeder valve that every propane tank is fitted with. After making the connection the bleeder of the destination tank is opened to "bleed off" vapor, thereby reducing pressure in the destination tank. Opening it wider reduces the pressure more, making the fill take less time at the expense of wasting a bit more propane. (Of course this is no problem out in the middle of a field where the gas dissipates as fast as it's vented, but definitely not recommended inside a building or if there is absolutely no wind.) If you watch the operator when they are filling your motor home tank, or a portable tank at the dealer, they will always open the bleeder at least a small amount even if using a pump. The bleeder is also a fail-safe level gauge. It is either on a tank fitting at the 80% level or is connected to a dip tube that reaches down to 80%. When the propane level in the tank reaches 80% the bleeder will start to spray liquid propane out, letting you know that the tank is full. Most motor home tanks are fitted with a float valve that blocks off the fill line around 80%, but it's not a good idea to rely on it. If it fails to shut off the tank could be accidentally filled completely full. Full tanks overpressure if the temperature rises, causing the relief valve to open. (Been there, had the soiled underwear to prove it!) It can also allow liquid propane to enter the regulator, possibly with dangerous results.

How do you get liquid propane at atmospheric pressure? Simple: release the pressure on it. The liquid will boil, causing it to cool down. As soon as it cools to below minus 44 degrees F it will stop boiling and remain a liquid. Of course it will continue to evaporate as it picks up heat from its surroundings, but in a well insulated container the evaporation rate can be quite low. While experimenting I would fill a thermos bottle with liquid. Closed off with a loosely fitted cork stopper it would remain liquid for hours.

 

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I stand corrected about using the bleeder valve to fill a tank above the level of the supply tank.  Yes, slightly cracking the bleeder on the tank to be filled would surely work.

As far as pouring liquid propane at atmospheric pressure, I've only tried discharging it (from the LIQUID port) into an open dish, and it evaporated as quickly as it hit the pan.  I could never accumulate liquid.  Perhaps if I had used another container with a small neck, I would have gotten  different result.

Thanks for your input.

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MH Rookie, I use my propane for my stove, my BBQ grill, and my Fire pit, which uses a lot of propane. What I do is when I am through for the year, I swing by our local Flying J, top off the fuel tank and then drive over to the propane tank and have them top it off too.   It's very convenient and their price is reasonable.

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Guest Ray Davis

Around here the dealers will not deliver less than 100 gals, and they don't like to drag the hose a long way either.  I'm sure it gets heavy dragging it all day.

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