LP Tank Gauge?

My propane distributor has magnetic gauge/OPD valves available for small propane cylinders (10, 20, 30 lb.). The gauge snaps on the outside of the OPD valve, and magnetically senses the float position.
I have one on a 20 lb. cylinder. It works great. When I get the other cylinder re-certified I will have the new OPD valve and gauge installed in it.
A propane "filling station" probably will not have the valves. It is likely that one would have to go to a propane distributor to get the valve changed.

What kind of an LP tank?

If it's a built-in ASME permanent tank, it should have a float gauge on it already and that's as accurate as anything. Often there's a sender attached to the float gauge dial (at least partly obscuring it) for a readout in the RV, which readout is often very much less precise than the actual gauge.

If it's a portable DOT cylinder, such as for a barbecue grill, probably the most accurate way to determine the propane level is by weight (though it's not very convenient to remove it and put it on a scale). The tare weight of the cylinder is stamped on the metal collar, and subtracting that from the total weight gives the weight of the propane. A 20 pound tank can safely hold up to 20 pounds of propane, though most exchange places gyp you out of five pounds and only fill them to 15 pounds.

The gauges that adhere to the outside and require one to pour warm water over them also work well, and operate based on the cooling of the liquid propane while drawing off gas. You can often achieve the same thing without the gauge by examining the cylinder for condensation or frost (perhaps after dampening it).

The pressure gauges that attach to the tank valve are useless for determining the quantity of propane left, as the pressure does not vary with propane level--it's always the vapor pressure of the propane at whatever temperature it's at. About all such a gauge can tell you is that you've run out of propane.

ricks99 wrote:
Anyone have recommendations for an LP Tank Gauge?

Nope - 'cause they don't work. :M For any gauge to read accurately it needs to read the liquid level of propane, not the vapour as all these so-called LP tank gauges do. :R If you want to know what's in the tank, weigh it. ;)