A working Auto Stop Valve does automatically stop propane from entering
the the filler port of the tank. There is a small external feed tube
from the tank's 80% port to a piston chamber in the auto valve section.
When the tank fills up, liquid comes from the 80% port through the tube
and forces the piston to slide over and block the filler passage. Once
this occurs, no more propane can be put in until the piston is reset, BY
HAND, via the button that was originally under a removable plastic cap.
Many times people who don't know about the reset button fail to get
their empty propane tank filled.

The weakness of the Auto Stop Valve has to do with the piston. It relies
on "O" rings to seal the bore it rides in. The "O" rings fail over time
and then propane leaks past. An entire tank of fresh propane may then
leak out while you stand there watching in fear and disgust. I have
installed new "O"rings on some but the repairs never lasted. I will
never repair one this way again. Either install new standard valves or
replace the tank.

Mark

Tim Demarest wrote:

> This is perfectly normal... there really doesn't seem to be anything
> "auto"
> about the auto-stop valve.
>
> The bleeder will always allow propane to escape if it is opened, it's
> plumbed directly to the correct fill level in the tank. When filling, the
> bleeder should be opened all the way, and filling should stop as soon as
> "liquid" propane emerges from the bleeder.
>
>
>
>
> At 07:12 PM 6/25/2005 -0400, Mike Collum wrote:
>
>> Sorry gang, I've played in the archives for a couple of days and found
>> tons of info ... but my particular question doesn't seem to be covered
>> well.  Manual valves are simple but the Autostop is new to me.
>>
>> With a propane tank that's not yet completely empty (stove still lights)
>> but has been used for cooking and fridge for several weekends of camping
>> ... is the bleeder hose supposed to hiss (let gas escape) when the
>> bleeder valve is opened (remember ... AUTOSTOP) or is it supposed to
>> remain silent until the tank is full?
>>
>> Any and all autostop info will be greatly appreciated as I haven't
>> filled the tank since I've had it (and it's time) and I'd like to know
>> it's working (or when it's not working right) before I condemn the thing
>> and go manual valve hunting.
>>
>> Thanks,
>>
>> Mike
>
>