Auto Stop Valve - Propane

[markopolo-ClassB]

If you have an older propane tank it might have an Auto Stop valve. The Auto Stop is no longer made. It uses a piston rather than a float to prevent overfilling the propane tank. The vent valve must be fully opened in order to fill the tank. If the vent valve is only partially open then the overfill protection will kick in and prevent you from filling the tank.

Notes: The reset button (to activate piston) cannot be pressed down unless the Vent valve is open.

It is functional but propane filling attendants might not know how it works.

Auto Stop valve filling instructions copied from the label:

This tank is equipped with an Auto Stop valve.
80% Automatic Stop Fill Valve Operation Instruction:
1. Make sure the vent is closed.
2. Connect hose to acme thread.
3. Turn on pump.
4. Open vent to start filling.
CAUTION! If filling rate is slow, or is not filling, press the opposite end of vent stem to activate piston. Filling should start immediately.
5. Vapor will discharge similar to standard vent valve.
6. When liquid appears, filling stops. Close vent stem.
7. Stop pump.
8. Place acme cap on valve
Auto Stop Corp
Lynwood, CA

You can purchase a Fill valve and a separate Bleeder valve to replace the Auto Stop valve. This will make the fill system the same as modern RV's. I think I have found high quality replacements. Cost is $30 or so for the parts. I will post the details once I speak to the company to confirm.

 

[markopolo-ClassB]

These are parts I ordered from PNG Technologies.

http://www.pngtechnologies.com/LPG-TANKS-AND-ACCESSORIES.html

Quick Fill Valve
Part # 7647SC
3/4" NPT
$ 16.99



80% Stop Bleeder
Part # 3165CP
Vavle - No Stem, 1/4" NPT



Obviously don't work on your propane system unless you absolutely know what your are doing. The tank has to be completely empty of propane. The vendor recommended using Teflon paste pipe dope rather than Teflon tape.

I'll update this thread again when I install them.

 

[markopolo-ClassB]

Somehow my order at PNG got lost before being processed so I had to order these parts again today.

 

[Johnny R]

Re: MarcoPolo's auto fill replacement. When I approached a propane shop here in Alberta, he said several things:
1. Although tanks need to be inspected every 7 years (in A, no shop is in the business of checking RV propane tanks. So the matter rests until the sh** hits the fan on a preventable accident.
2. If, however, the shop replaces the fill valve, then the shop will inspect the tank very carefully, including rust etc etc etc.
The message he was conveying was: In Alberta, leave it alone!

 

[markopolo-ClassB]

If it ain't broke don't fix it

I had the tank filled recently. I'm glad I had the instructions and had read up on this type of valve. The attendant tried filling the tank for 5 minutes before telling me that my gauge probably didn't work and the tank must be full because only a small amount of propane went in. Like $2 worth. He had never seen an Auto Stop valve.

He was patient though and when I asked him to make sure the vent was fully open and try again he did and it took $25 + of propane!

So for now I'll keep the Auto Stop valve because it works. I did finally receive the new modern type fill valve and bleeder valve that I ordered so I'm ready to replace it all if necessary.

 

[markopolo-ClassB]

This is a very old topic but I'm adding some info that might help others even service techs. Also, have a trained propane professional do any propane related work.

First: This site has great photos of the Auto Stop valve: The Infamous Auto Stop Propane Fill Valve. | arts-attic.com - A copy of the patent is also on that site.

Next: The body of the Auto Stop valve separates from the hex (nut/bolt) fitting. The hex fitting is a bushing with very fine threads on the hex to Auto Stop side and NPT threads on the hex to tank part. This means that you can remove the Auto Stop valve body to gain access to the hex fitting.

I discovered that by accident. I couldn't access the hex nut fitting so I used a plumbers slip nut wrench to rotate the Auto Stop valve body. The fine thread fooled me into thinking that it was swivel type coupling as it didn't seem come away from the hex nut. Rotating the Auto Stop valve body a bit did permit some access to the hex fitting but I soon got stymied there. So I went back to the Auto Stop valve body and discovered that it was coming away from the hex fitting as I rotated it. Once the Auto Stop valve body was removed then it was easy to remove the hex fitting.

The new valve was installed in less than a minute as I had a 1-3/4" socket ready to go. The new bleeder valve was also easy to install.

I have a combination of fittings that allows me to transfer some liquid propane from a BBQ tank to the approximate 40lb ASME tank on the van. The transfer was pretty quick and the tank gauge moved to 15% confirming the transfer as well as the new unused Exchange type BBQ tank had reduced to 1/4 full. (Exchange tanks have 15 to 16 lbs of propane from what I've read)

Note that the new fill valve is not an OPD type. This means that the bleeder or spit valve has to be open to know when the tank is at 80% full. Always make sure that the filling attendant opens that bleeder valve. From what I've read on the internet, it seems that there is no federal or national requirement that ASME tanks have an OPD fill. Some states do mandate that though so do your research. DOT cylinders must have an OPD fill valve.

I don't think that an OPD fill valve is available for the tank on my van as the fill inlet looks to be at the 50% level so considerably lower than the bleeder valve. Newer tanks appear to have the fill & bleeder at the same level (80%).

In my experience, filling attendants always open the bleeder valve anyway but I have read that sometimes they don't. I'll just make sure that the filling attendant opens that bleeder valve.

Note: Any work on the propane system should be done by trained professionals.