Trying to understand how one propane tank can run fine connected to either a grill or another propane-powered device (mosquito magnet), but not one of the three just-exchanged, full tanks will puff a whiff of gas into either the grill or the mosquito magnet.

I got a propane tank gauge, and that works fine on the old tank as connected to both the grill and mosquito magnet....but when connected in line to the three fresh tanks...nothing shows on the gauge and nothing flows.

I've used propane tanks since the '80s, and never seen anything like this. My ability to connect the other tank and the propane gauge and have everything work makes me think it's not me, but for all three of the newly-exchanged ones to fail in this way seems statistically unlikely.

I have the receipt (exchanged in June at the local Tru-Value) so I can go back and see about getting them replaced....but, how will I know if the replacements would be better than the June trio? It's not like you can crack the valve and listen for the flow. (safety valves)

This being SIGforum, I'll bet one of us:

a) has seen and overcome this, and/or
b) knows what I'm doing wrong, and/or
c) knows the underlying reason for the issue, knows what I should tell the guys at Tru-Value, and has advice as to how I can know at the store the new ones will work correctly.

I'd appreciate any insights the membership could contribute. I'm using the old propane tank (gauge says it's mostly full!) but within a month or so I'm going to need some working replacements.

How is the weight of the tanks vs how they normally feel when full?

The three all weigh essentially the same, 33lb, according to the bathroom scale.

If they were laid on their sides during handing or shipping, and the internal safety shutoff engaged, all you will get is a small amount of flow. (or if you open the valve fast without regulator or gas knobs shutoff)

With the tank upright, close the valve, disconnect the tank and let it set for a few minutes, then reconnect, make sure the grill knobs are shut off, and slowly open the valve and see if it works.

Don’t know if this might help, but I use Mopeka tank sensors. They seem to be very accurate showing the tank levels. They attach to bottom of cylinder by magnet.

I recently had this problem as well, with a Rapid Xchange brand tank. The tank is full, and it pegs my pressure gauge, but it acts like it has a flow restriction. Propane flows, but my larger grill won't light all the burners and struggles to get above ~175 degrees. My smaller grill won't go past about 300 degrees. Both grills work fine with other tanks.

I have no idea what the problem is, but it's frustrating.

That's a safety valve; it's happened to me also - the grill lit, but didn't get very hot.
You have to have the burners off and the tank valve shut.
Open the tank valve with the burners off and then use the burner control to light the grill.
If a burner is not off when you open the tank valve the quick flow of gas causes the safety to trip and only a slight amount of gas flows.

It’s the internal safety stop valve. Basically a flat washer held open by a weak spring. If the gas hits that washer to hard it snaps shut.

Like has been said close everything up disconnect the hose. Reattach and slowly open tank valve giving plenty of time for pressure to equalize between tank and appliance.

It will present worse as temperatures increase. Be patient it might gut take a couple tries to get onto it.

Those tank exchanges are a screw job, your paying 20lb fill price but only getting around 15lb of propane, not to mention near expired tanks.

That’s one of the reasons I have my own tanks and get them refilled. Bad valves and I don’t like paying more for less.

quote:

Originally posted by mark60:
That’s one of the reasons I have my own tanks and get them refilled. Bad valves and I don’t like paying more for less.

I've been doing this for a few years now too. Bought my own tanks from Lowes and get them filled at Tractor Supply. Did the math and it's way less than paying for an exchange tank and I know I'm not getting a junk tank.

I’ve had two bad tanks in the last two years as well.

I've filled tens of thousands of propane cylinders, mostly forklift. I have eight 20# cylinders that are spotlessly clean, no rust, no dents. I watch Ace hardware (love em) put 20 pounds in, not fifteen. I have several with the twelve year test date coming due. Ace won't fill them. I don't blame them. They will take them off my hands and sell them to a company that will take one look at it and stamp a new test date on it and sell it to a gas station exchange place. Those OPD valves aren't indestructible, people beat the hell out of them. If the cylinder is upright for a while, the valve should work properly.

Turn off valve remove hose.
Turn valve on
Turn valve off
Attach hose.
Make sure grill burners are OFF (important)
Turn valve on VERY slowly - you'll hear a quiet click if the safety valve trips.

I've had it take 2 or 3 tries, but I haven't had any that wouldn't work at all.
I get mine mostly filled, but I have had the issue with those as well, and not just when full. If I leave the burners on & open the tank, it will trip most of the time.

I filled 100s maybe 1000s of 20lb cyls back in high school and a hand full came back with this same problem. Being ignorant but a problem solver, I would usually drain them ~10% via the purge valve, then try on the grill we had at the gas station. It would work. Then I'd refill (to weight) and try again. Don't remember many failures, but that was 25 years ago.
Notice that I didn't suggest draining via the purge to fix your problem. I've done it, but it's not necessary. I don't usually keep a screwdriver near the grill, so it's faster to do the method above.

Appreciate all the advice! I'm going to give it a try tonight, and hopefully I'll be back in business!

Thanks for the inputs, all. Now I have some experiments to run, hopefully this weekend.

New tanks aren't all that expensive considering a normal lifetime when stored under a roof without exposure to weather. I NEVER do the tank exchanges, don't trust them at all. I get mine refilled by operators who know how to avoid overfilling, since I had a tank that was overfilled once and I didn't know it, until it started hissing sitting in the sun. At that time I figured it was a safety over pressure release valve, but I was nervous because I didn't know about that feature at that time. So I moved it off as far as my garden hose water could each, under a tree in the shade, and hosed it down for 20 mins. If I had known it then I would have released some pressure using a straight slot screwdriver.

quote:

Originally posted by wrightd:
I get mine refilled by operators who know how to avoid overfilling

A properly functioning OPD valve (mandated in the early 2000's) prevents an operator from over filling. But even still, they have to put it on a scale and fill by weight. A 20# cylinder is designed to hold 20 pounds. Gas station exchanges put only 15 pounds in for liability reasons. Even the old valves had a pressure relief devise on the opposite side of the outlet so if the temp and pressure gets too high, it intentionally releases gas so the cylinder doesn't explode, which can be bad. Many times someone would get a filled cylinder, put in the trunk on a 94 degree day, and decide to stop at the mall for three hours. The pressure relief devise does it's job and fills the car with propane, come out and push the electronic trunk release and.. umm, lets see who has the deepest pockets.

Well if a properly filled tank can't handle a hot summer day in direct sun then I'd call that overfilled. So if 20 lbs is too much for hot sun then filling below 20 sounds prudent. If you're using it to heat a camper in the winter that's one thing, so maybe summer use adjustments are needed. I don't really know. I don't like the idea of putting my life in the hands of a 20 dollar over-pressure valve from china.

quote:

Originally posted by wrightd:
Well if a properly filled tank can't handle a hot summer day in direct sun then I'd call that overfilled. So if 20 lbs is too much for hot sun then filling below 20 sounds prudent. If you're using it to heat a camper in the winter that's one thing, so maybe summer use adjustments are needed. I don't really know. I don't like the idea of putting my life in the hands of a 20 dollar over-pressure valve from china.

I didn't mean any offence. It's the industry I worked in for forty years. A good cylinder with a good OPD valve can sit in the sun all day without leaking. Gas grills sit in the sun all day. You had a bad valve. And the slotted screwdriver, we called it a spitter valve!
My one minute of training forty years ago, no weighing, open the spitter, when liquid propane spits out it's full. way over full.
I drove the trucks, in my last years if I wanted to fill one propane cylinder, I would have had to take eight hours of training! LOL. No thanks. It is wise to keep them out of the sun.