20 lb propane tanks

The guy that fills mine. Weighs it before he fills it. then fills it to the point the gas comes out of the over flow valve, and weighs it again, and charges me for the difference.

Yea lets all do the exchange to get 15 lbs. of propane for 20% more money.
Nope, I will stick with 30 lb. tanks filled with 30 lbs. propane from a propane dealer.

The reason why 20# containers (cylinders which actually have more than that, but are rated for 20#s) hold 16# is because a propane exchange place only has to use 3.6 gallons to fill up a 4.7 gallon tank... 75% of the fuel for 100% of the profit.

The tank is rated at 20#, which means that it isn't unsafe to fill it with 4.7 gallons of fuel. In theory, 4.69 gallons of fuel, because after 4.7, the OPD should cut in and stop the filling.

Of course, there is the convenience aspect of exchanges, which makes paying $20 for less fuel worth it. If I want a tank filled, it is a drive out of Austin to a RV park, RV dealer, or a propane place in one of the smaller towns.

spadoctor wrote:
As for the 20's....the fed regulation says no more then 17 lbs in them now because of issues with the OPD floats. That's why the exchanges have gone to 15 lbs. There is no lower fill requirement on the 30's. This per 2 LP dealers and my county health dept that does weights and measures

vic46 wrote:
Are you saying that the 80% fill limit is not mandatory on 30# tanks?

A 30 lb tank when filled to 80% capacity will contain 30 lbs of LPG. Check the collar on any 30 lb tank and it will have a WC (Water Capacity) rating of ~ 71.3 ... 71.3 x .42 = 29.946 lbs. This has nothing to do with OPD valves which have been mandated since the late 90s ... wherever spadoctor is getting his info it's incorrect.

spadoctor wrote:
LP portable tanks are VISUALLY recertified for 5 years at propane dealers. My guy does it for free when refilling. They use 20 lb tanks for cost savings since they offer an upgrade to 30 lb. As for the 20's....the fed regulation says no more then 17 lbs in them now because of issues with the OPD floats. That's why the exchanges have gone to 15 lbs. There is no lower fill requirement on the 30's. This per 2 LP dealers and my county health dept that does weights and measures

Are you saying that the 80% fill limit is not mandatory on 30# tanks?

Mine has 2x20 and I'm glad. So easy to just swap them out just about anywhere instead of having to search for a place that fills tanks.

20# tanks used to be the standard. But now I am showing my age.

Just had one of my 30lb cylinders re-certified at a propane company office. The cost was $10 and apparently good for 5 more years. I plan on the re-certification process until the gov't tells me otherwise.

The 20lb exchange program is much more expensive then having the cylinders refilled, and the only time I exchanged was to get a tank that was already (re)certified.

Road Phantom wrote:
I noticed that some of the new model trailers are coming with 20 lb propane tanks like the ones they sell at Walmart and other retailers. I can see the convenience of that. Anyone change their tanks to accommodate them instead of the standard 30 pounders?

Our previous KZ Spree came with twin 30 lb tanks and I never gave it much thought, other than after filling I had to lift the stupid things into position on the trailer. :E Our current Freedom Express came with twin 20 lb tanks and I find them much easier to lift into position. We camp from April to Nov and because I keep the trailer here at the house I use it often including the furnace yet find I usually only have to refill one of the 20 pounders once during the season. With 30 pounders I could avoid filling during the season entirely but on the weight argument alone I'd far rather stick with the 20 pounders I now have. :B

Regarding filling by weight I see the old wives tale about the "80% rule" still abounds ... BUT the reality is a "20 lb" propane tank does contain 20 lbs of liquid propane gas when filled to 80% capacity. On the tank collar is the tank's WC (Water Capacity) rating ... multiply WC by .42 and you'll have the tank's propane capacity as measured in pounds. For example, one of my 20 lb tanks has a WC of 47.6 ... multiply times .42 and we have 19.992 lbs. Also on the tank's collar is it's tare weight (TW) or empty weight ... mine is 18 lbs so when that tank has been properly filled to 80% capacity with 20 lbs of liquid propane gas it should weigh 20 + 18 = 38 lbs. I had this tank filled just last week and indeed it weighed right around 38 lbs. Here are details on filling by weight, including a simple cylinder filling chart.

Depends greatly on how you use the RV.

Winter camping or boondocking with the fridge on propane and the big tanks are well worth it for the longer time between fill ups.

If you mostly camp in the summer and just do a little cooking, you should easily be able to get a full summer out of a pair of the small tanks plus in today's world, it is easier to get refills as most have gone to exchange systems.

My guess for why though is likely cost as the BBQ tanks are mass produced at a much higher number.