[RockyMtnRay]

Originally Posted by Eric Larson

Our new 2720sl came equipped with horizontal propane tanks. Each gauge has (2) scales working off the same dial indicator. One scale is for reading tank pressure in the horizontal position and the other scale is for reading tank pressure in the vertical position. The gauges on both tanks indicated that the dealer had only filled them slightly more than 1/2 full when we picked up the trailer. Since we are getting ready for our first RV experience in the TM -- I pulled the tanks and took them to be topped off. But both were already full and spewed white liquid as soon as the attendent pressurized them (filling is performed only in the vertical position). I was wondering if these type of gauges are just inherently inaccurate or if they are actually defective. Can anyone enlighten me ?

Whether or not the horizontal tanks say to fill vertically or horizontally, the reason you did not...nor will not...be able to fill them more than much above the 1/2 full point on the gauges is the OPD (overfill protection device). An OPD is a float valve inside the tank that's specifically designed to prevent the tanks from being filled beyond the 80% point. The reason an OPD exists is to prevent overfill. If overfill does occur, there isn't enough expansion room on warm day, which in turn will cause the emergency overpressure vent valve to open. If that valve opens and the tank is inside a closed area (e.g a garage) then the area will fairly quickly fill with vented gas and even a tiny spark will ignite it (propane is heavier than air). Result: a huge explosion and fire. Like at the the Electric Mountain Lodge here in Colorado last winter

There was a problem with the OPD on one of the tanks on my TM when it was delivered...it actually would allow complete filling of that tank. That tank would indicate "F" after filling...the other tank would only indicate about 2/3 after filling. I thought the tank that would only fill to 2/3 had something wrong with the gauge.

And then one day, I heard and smelled gas escaping from the tank (the one that was indicating "F") after it had been in the afternoon sun for a couple of hours. Turning off the tank valve did not stop the escaping gas...it stopped only after the sun dropped enough that the tank was shaded. Thankfully the trailer was outside and there was a decent breeze to waft away the escaping propane...or I (or my TM) probably wouldn't be here today. A few weeks later, I received a recall notice from Manchester Tank (the manufacturer of the tanks on my TM) advising me that I may have defective OPDs and instructing me on how to get the OPDs replaced before next use. Manchester followed up by sending new OPDs for both tanks and paid for a local propane distributor to properly change them out. Now neither tank indicates above 2/3 when "filled" and I couldn't be happier about that.

If you look really, really close at the gauge you'll likely see the actual level when "full" is about 2/3. If the propane fill facility has very high pressure pumps, it might be 3/4. But if the OPD is working correctly...and in light of my experience, you better hope that it is...then you'll never see more than 3/4 on the gauge after a fillup.