Why would it have to go before the regulator?

I was imagining a shutoff valve at the disposable bottle's connection, and
if the main tank it empty, just close that valve and open the valve for the
little propane botttle.  You don't need a regulator for the little bottle
right?

>From: Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
>Reply-To: Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
>To: vanagon@GERRY.VANAGON.COM
>Subject: Re: Propane Disposable Bottle Hookup
>Date: Fri, 17 Feb 2006 20:01:28 -0500
>
>Yeah, it's the not knowing how much you have left, and when it is going to
>leave you empty.  I guess another alternative is to just get it refilled
>more often, even if you might not need it.
>
>You need to put the disposable tank in the system before the
>regulator.  That's why all the talk of hooking the dispo tank to the westy
>tank somehow.  Hmmm, you give me a new idea.  How about another regulator
>and dispo tank hookup under the sink?  Will the regulator safely act as a
>one way valve?
>
>Edward
>
>At 12:19 AM 2/17/2006, you wrote:
>>I agree that the a 3 gallon propane tank lasts a surprisingly long time.
>>But without a level indicator it sometimes runs out at the worst possible
>>time.  And mine has trouble filling so, I perfer to wait til it is
>>completely out before trying.  [Those propane monkeys always tell me there
>>is something wrong, until they finally figure it out.  And half the time
>>they won't let me show them how to do it.]
>>
>>So what is the best way to tie in an adapter for a portable container.  I
>>assume in the line that runs through the cabinet and some sort of T
>>fitting.
>>
>>
>>>From: Tom Buese <bueses@EARTHLINK.NET>
>>>Reply-To: Tom Buese <bueses@EARTHLINK.NET>
>>>To: vanagon@GERRY.VANAGON.COM
>>>Subject: Re: Propane tank fill valve anatomy
>>>Date: Thu, 16 Feb 2006 20:37:50 -0700
>>>
>>>.................
>>>The experience that made me really want to have the ability to hook up a
>>> >disposable bottle temporarily to my Westy tank was last Easter weekend.
>>>I
>>> >was camping on the shore of SC and ran out of propane.  There was no
>>>place
>>> >that could fill a Westy's tank on Easter Weekend for 100 miles or so.
>>>I
>>> >was not camping where there were hookups, and not driving around enough
>>>to
>>> >keep my aux batt charged and run the fridge off that.  So no fridge and
>>>no
>>> >stove to cook.  Frustrating.  That had happened on an earlier trip
>>> >too.  Not quite as frustrating, but still ran out one evening, and
>>>watched
>>> >the fridge warm up all night.  The next day I found a place to fill the
>>> >tank, but it was out of my way, and took some digging to find, and
>>>blah,
>>> >blah, blah, I would have rather been cruising the backroads of WV in my
>>>VW
>>> >with no cares.  I would just carry a partially filled disposable tank,
>>> >having carefully refilled it at home from a big tank, and have it as
>>> >reserve capacity to tide me over in emergencies.
>>>.................
>>>
>>>I might have missed this part of the discussion, but I go months w/o
>>>using
>>>much propane.  How long are you using the fuel before you run out on a
>>>trip? Before my recent DV trip, I pulled into my propane place & it only
>>>took 1.3 gallons after a week at Burning Man, & 3 weekend camping trips
>>>after that, w/ one trip including running my 3000 btu catalytic heater
>>>for
>>>part of a day. Now I will admit I don't use the propane for my fridge,
>>>but
>>>do use it for cooking & heat.
>>>
>>>Pax,
>>>
>>>Tom