I've read a lot about how to fill smaller propane tanks (20 lb through 100lb tanks) from a larger tank (I have a 500 gallon tank) from the larger tank's wet leg.  I also discovered that there's a lot of talk on the internet but not much information on how to do it....at least what I could find.

So, I searched around and found a kit.  Some people piece kits together but this kit is made to fill tanks specifically:
Kit link

When you fill the smaller tank from the bigger tank, the smaller tank will have pressure build until it equalizes with the larger tank.  When that happens, the propane flow stops.  So, you have to shut off the liquid flow and open the small valve on the adapter so you can drop the pressure in the smaller tank below the bigger tank.  You then close the vent valve and re-open the liquid valve.  For a small 20 lb tank you only have to vent it once to fill the tank.   But for the larger 100lb tank, I had to vent the pressure every 5-10 lbs to keep the flow going.  

Here's the kit as delivered:




I used the included Teflon tape and put it all together:




This is the cap on the 500 gallon propane tank wet leg:




This is looking into the wet leg valve after the cap is removed:




This is the valve connected:




Here it is filling a 20 lb tank.  The tank is sitting on a regular analog bathroom scale:




20 lb tank before filling:




20 lb tank after filling:




100 lb tank being hooked up:




100 lb tank before filling:




100 lb tank after filling:




Valve installed on a tank:




Releasing pressure from the smaller tank to allow liquid propane to flow into the smaller tank

I filled two 100 lb tanks and one 20 lb tank in about 1 hr.  The 100 lb tanks take awhile to fill but the 20 lb tanks fill quickly.

Cool.
Do all propane tanks have a wet leg? What is a wet leg?

I thought you were to only fill tanks to 80%? Your 20lb tank shows 20lbs empty and over 40lbs full.

It's a cheap scale from Wal-Mart and it's off a bit. Reads too high. I'll fill the next tank to about 38 lbs. Going to be using that one immediately.

A wet leg is a tube that extends down into the liquid propane in the big tank that allows liquid propane withdrawal.  

I don't know if all propane tanks have them but many do. Most actually in my area.

Is it labeled as such?

very interesting post.. thanks for sharing...  im going to check my 120 gal tank to see if it has that connection

I was interested until i saw the kits cost..  $200,  i would never get my moneys worth..


brian

If the cylinder has an opd valve, I just fill until the safety shuts off the flow.

On standard valve, I fill until liquid starts spitting out the breather.


Just thought I'd mention it,

When I filled that 20lb tank I stopped before it tripped the OPD.

I realize it's not for everyone. However, when I fill a 100 lb tank at the supplier, I pay about $2.10 per gallon presently. When I fill it from my home tank, I currently pay $ .99 per gallon. So, I saved about $50 today.

From a survival perspective, it could come in handy to scrounge propane in a major disaster. Unlikely I realize so the main reason I got it was for saving money to fill propane tanks. It's also nice to be able to top off partially filled tanks.

Thanks very much.

OP, thanks for posting this.

Just a heads-up for folks who may have buried LP bulk tanks:  The 6' hose in the kit may be on the short side to go from the wet leg interface, through the access riser (the metal or plastic "pipe" that lets Propane Dude fill the tank), and then on to the target small tank. I may see if I can make my own kit.

A bit off subject but can the small tanks (such as purchased at Wal-Mart and such) for lanterns, camp propane stoves, etc. be filled in such a manner (with special adapters)?

I fill the "disposable" 1 pound bottles all the time from 20 and 30 pound tanks.

 

The cute little 1 piece inline adapters they sell to do the job suck, made my own.


Couple things of note:

If you are not 100% familiar and comfortable with propane and propane systems, don't refill 1 pound bottles.

It is AGAINST FEDERAL LAW to transport disposable bottles that have been refilled.

You WILL fill them to more than 80% using my method. In fact, you could fill them to 100%. I don't store filled units, I only fill them when I need them.

It is easy to have leaks on the 1 pound bottles after you re-fill them. They should be checked for leaks, and ideally used immediately.

Less than perfect 1 pound bottles should NEVER be filled, but disposed of. Do NOT refill rusty bottles.

I fill 1lb tanks all the time. Fill them from 20 lb tanks. I have the adapter for them. Think it's about $20 or so. Some people leave the 20 lb tank in the sun and freeze the 1 lb tank. That works but doesn't get max fill. It does get close though. I use some surgical forceps and gently pry the little valve open to help relieve the pressure in the small tank. That allows a true 1lb fill.

MUCH MUCH cheaper to fill that way than to buy the small tanks.

Good post!!!

FWIW, I've NEVER seen a tank filled in that manner. Typically the bleeder is opened at the same time as the liquid line. If you notice, the bleeder is pointed down at the tank, this serves 2 purposes. #1 It keeps the vapor pointed away from you (it can cause instant frost-bite), #2 The cold vapor blowing on the tank lowers the temperature of the tank: lower temp = lower vapor pressure = liquid freely flows/condenses into the tank.

If you wish to fill the tank without wasting the propane (cracking the bleeder) you can open the valve and allow the tank to set connected in the evening. The large tank is at X temperature, and as the outside atmospheric temp drops the small tank will cool at a faster rate because of it's lower volume : surface area ratio. Therefore, lower temp in the small tank equals lower vapor pressure = liquid will flow to the small tank. If you want to jump-start the flow of LP you can put the empty tank in a freezer first. Caution: it is very possible to overfill tanks this way. I suggest you keep a close eye on it or you take it off plenty early.

Does proper disposal mean filling and using for target practice?

Only worth it if you run tracers

 

But seriously, don't bother. They will leak after you fill, so you will have an open/active propane leak and NO WAY to stop it.

Be very careful when you remove any cap or device from the liquid withdrawal valve, if it does not seal correctly ...........there is no plan B.
( There is no way to stop the flow of liquid )
.
Inside the brass cap be very careful not to loose the nylon seal.

One thing I thought I might mention about propane.

Background: I grew up in a propane family. As in there was a family propane delivery business. There were many propane trucks in and out of the farm, and a HUGE propane tank (as in takes two propane tanker semi trucks to fill it) as well. Don't even start bothering to count how many 500 gallon tanks were around...


We were trained as to what to do if there was a fire: cool the tank. Scenario: popped relief valve, and the escaping propane catches fire for some reason. Perhaps there is a fire by the tank, whatever. Don't put out the flames!!!!!!!!!!!!!!! Keep directing water toward the main tank to keep it cool. Once the propane burns, its gone. If it doesn't burn, it builds up.


Now, this was the job of the men while the women/children were evacuating. Once everybody else was gone, the men would rig the hoses to keep cooling the tank and GTFO. Fire department was in on everything, and while everything depended on the situation, they figured a lot of scenarios meant let it burn: too risky to get near the thing, nothing around anyway (done on purpose).


Not advocating anybody should stick around and do the same, but there was enough propane there to make national news if S hit the F. We had to make sure everybody (including about 3 neighbors) was out and cooling the tank buys time.


Not even sure why I posted, other than a leaking propane tank is deadly serious. Be aware of what to do.

Good point... Also a good idea to stock some spare nylon gaskets...


One way to mitigate a leaking wet leg  issue  -to a large degree, is to use the REGO 7590U-20 check lock valve actuator/adapter that has a manually controlled plunger that depresses or releases the wet leg valve port.

A shut-off valve needs to be installed on the 1" outlet port of the REGO valve and then connected to your delivery hose.


Once the REGO valve is installed on the wet-leg you rotate the lever on the side to depress the tank mounted valve 'stem'  to open the wet leg valve.

If the tank wet leg valve doesn't re-seal, it will be obvious and the tank content can be preserved by closing the secondary valve installed on the REGO valve.

Here's pictures of the REGO valve plunger in the extended and retracted positions.

Note the handle position.

The other valve is a 'fill' valve, and isn't a factor to this illustration.










The tank in the pix is a 120 gallon...


Here's a PDF of the almost essential to have REGO catalog full of safety, training, installation, use, and product info.

It's a component of my technical Dropbox library.


REGO

You are referring to the tanks at the Tank 'exchange' places. Those are generally never filled to capacity. You PAY for 20 lbs of propane and actually GET 16 or so.

A 'normal' tank will have the Tare weight (empty tank weight) printed on the side very visibly and will indeed safely hold the advertised 20 lbs of propane.