So- that title is strange and possibly doesn't fit what I'm trying to say. But what I'm saying is have a little bit of knowledge about what you deal with... even if you can't do it yourself.
Today I had to go down and have my 100lb propane tank filled. Obviously I can't do that myself. But I'm glad I know a little bit about it. What I do know is:
-Over flow protection valves do NOT come on 100lb tanks (indicated by no triangle valve knob and the warning stickers on the tank )
-Completely empty (new) these tanks hold approx 22.3 gallons of propane
-To fill the tank, you start flowing propane and open that valve on the side. When it starts throwing out liquid instead of gas from that valve- your tanks is at the "safe by volume" mark and you should stop filling.
Why does it matter that I (or you if you need to fill these) should know this??
Today I took my 100lb tank down to a U-Haul to have it filled for the g/h heater. First I made sure that his tag said "Propane Certified" CHECK. Even better, it said "General Manager", but I still didn't trust him. So I walked with him back out to my truck as he left to fill it. As he's getting the hose hooked to my tank he says "I haven't filled many of these, what do they hold?" I stated "22.3 lbs bone dry. I generally get 18.5 gallons since I don't run them all the way empty." So on he goes filling my tank..... Without opening that little valve I always see get opened. Finally at 20lbs I say "Shouldn't that valve be open to know when it's full??" at this point he informs me "I just wanted to get close to the fill- there is a safety valve that will tell us it's full anyway." (refer back to "what i know" above to see there is no valve on this tank.) As I'm telling him I'm pretty sure there is not he finally opens that valve and it's blowing liquid. uhm... that means it's full right? NOPE he keeps filling it to 27gallons. So I pay, and leave thinking I must not be remembering correctly!! I get home, run a search.. yep 22gallons.
Long story short- I call him back and tell him he put too much in, he again tells me they can't be over filled and besides there is a pressure relief valve. So, I call the Arizona propane association, they inform me that 27 gallons of propane probably shouldn't even fit in the tank! They get another higher up person to confirm this is not good... As they're telling me to go ahead and hook it to my heater right away and run it full blast to get the pressure down, I walk out to my truck to find it leaking. As I tell them this, they tell me to take it right away to ameri-gas where they can safely and quickly burn off the gas. Lets remember I had my truck parked in the shade to keep the pressure from going up to fast. But in Az we have wide swinging temps. Our nights are about 40 and are days are like 80. They 3 wayed in the head guy from ameri-gas so he was expecting me. By the time we got there it was leaking quite bad. They opened the main valve and it threw liquid. At that point they said the tank was all the way filled with liquid with no room for expansion and quickly burned off some through a pipe that was like 50 ft in the air with a burner.
By the time I got back to the u-haul place the guy was already processing my credit. (It turns out ameri-gas provides that place their gas, had already contacted him and set up a "class" for this Thursday. So now the tank can safely be hooked up to my greenhouse... only 3 hours after it was filled. I would not have been happy to have that valve pop while the pilot light for the heater was on! That could have been baaad.
So learn just a little about everything you deal with. And stay safe.