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Air tank problems

Old 02-16-14, 11:12 AM
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Air tank problems

I have a 7 gallon air tank that is basically new. I took it to the gas station to fill it up with air. It filled to 80 psi in a few minutes. Next time, it filled to 40 psi and then it would not fill anymore. Today it filled to 20 psi and that’s it.

What is going on? Stuck check valve? Any ideas?

thanks
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Old 02-16-14, 11:22 AM
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How are you confirming that that's all it's take? If by a gauge on the tank itself, possibly it's a gauge problem. Or it might be an air supply problem.

It could be, but most likely isn't valve problem because these valves aren't regulators of any kind, they are either open or closed. If partly open they might restrict the flow making it take longer to fill, but they wouldn't reduce final pressure.
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Old 02-16-14, 11:23 AM
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Is there a setting on the gas station air pump? Maybe you have to remove the limitation there.
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Old 02-16-14, 11:27 AM
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The gauge might be off but releasing the air from the tank shows the gauge decrease. It also is not putting out the same pressure as before going just by the sound. I know that is not very accurate but it is definitely different today at 20 psi than from the 80 psi previously.
I am using the same gas station to fill up the tank.
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Old 02-16-14, 11:39 AM
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Originally Posted by robabeatle View Post
The gauge might be off but releasing the air from the tank shows the gauge decrease. It also is not putting out the same pressure as before going just by the sound. I know that is not very accurate but it is definitely different today at 20 psi than from the 80 psi previously.
I am using the same gas station to fill up the tank.
Normally there is no regulator built into the fill side of the tank's manifold. Consider that even if you're filling at the same station, there may be a difference in line pressure. For example, if the compressor isn't on, it might have had 80psi in the tank a few days ago, which was being drawn down as folks filled tires and tanks.

When you fill a tire or tank through a valve air will flow until it reaches equilibrium between the supply line and the tank. Then it stops flowing and you disconnect allowing the valves to close. So if the tank stops filling at a lower pressure, the first (and almost only) thing to suspect is that the fill line pressure is lower.
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Old 02-16-14, 12:55 PM
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Are you going to the gas station after hours? Maybe they switch off the shop compressor when they go home and the system leaks off, or someone got there before you to air their tires.
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Old 02-16-14, 02:09 PM
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I'm with FB on this one, your tank is a fairly simple system, typically just a thumbwheel valve that you can open and close, and a Schrader valve for the fill. As long as they are both open, even a little, the air in the tank will eventually come up to the pressure in the line. Being the weekend the compressor is likely turned off and the station's tank is being run down.
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Old 02-16-14, 03:35 PM
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So how do you know what the air pressure is in your tires if you don't have a gauge?
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Old 02-16-14, 03:56 PM
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Originally Posted by Bill Kapaun View Post
So how do you know what the air pressure is in your tires if you don't have a gauge?
He didn't say he didn't have a gauge. He must have one since he reports that the tank will only fill to a measured low pressure.

As I said earlier, and others concurred, he's probably dealing low line pressure at a fill station whose compressor is not under power, and the tank is running down. This is common, especially after hours because of concern about a leak or blowout causing the compressor to run all night and overheat.
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Old 02-16-14, 05:27 PM
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OKay, guys. Thanks. If it is the pressure on the fill side I guess I am out of luck. I wanted to use this air tank so that I didnt need a compressor but if I can’t just pop over to the station then it is more hassle than not.

THanks.
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Old 02-16-14, 05:41 PM
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Originally Posted by robabeatle View Post
OKay, guys. Thanks. If it is the pressure on the fill side I guess I am out of luck. I wanted to use this air tank so that I didnt need a compressor but if I can’t just pop over to the station then it is more hassle than not.

THanks.
If the station is open, you can ask them to flip the switch on the air pump to pressure up the tank. Are you inflating MTB tires so you can use as little as 80 lb. That wouldn't work for road bikes mostly.
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Old 02-16-14, 05:54 PM
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Originally Posted by robabeatle View Post
OKay, guys. Thanks. If it is the pressure on the fill side I guess I am out of luck. I wanted to use this air tank so that I didnt need a compressor but if I can’t just pop over to the station then it is more hassle than not.

THanks.
Don't give up. It's still as good as you hoped, just go to the gas station when they're open, or be the first one after they close. You got 80psi the first time, no reason you can't get that or more in the future.

However there may be worse news. The tank starting pressure is he most you can get out of it. However you can't even get that. If you use it only for topping off tires you may do OK, but if you fill tire, each tire will drop the pressure according to the ratio between the tire and tank volume. For example if you start wih 80psi, and fill a tire that uses 1/4 of the air, you'll end up with 60psi in both the tank and tire. The next tire will drop the pessure by the same 25% leaving you with 45psi. and so on.
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Old 02-16-14, 06:16 PM
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The stations that I go to are open 24/7 but it may be that they turn off the compressor as stated.

My use for this tank is to set up tubeless mtb tires, and have on my mtb rides in case a tire blows off the wheel.
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Old 02-16-14, 06:33 PM
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Originally Posted by robabeatle View Post
The stations that I go to are open 24/7 but it may be that they turn off the compressor as stated.

My use for this tank is to set up tubeless mtb tires, and have on my mtb rides in case a tire blows off the wheel.
If this doesn't work out for you, here's an alternative. Visit a Scuba shop and ask if they have a used aluminum 80cuft tank to sell you. Before accepting it ask about the last visual and Hydro inspection. Visuals are required every year or two, but are cheap, Hydrostatic testing is required every 5 years, and will be stamped into the top of the tank, and are costly so you don't want a tank 4 years past the last hydro date.

Then you'll also need a used (possibly no longer fir to dive) regulator. These normally output between 90 and 125psi, but can be set to anything.

Scupa tanks are filled to 3000psi, and 80cubit feet at that pressure will reliably fill a good number of tires. Then refilling the tank will cost you between 5-$10.00.

This is the best way to provide field air at events because it doesn't require any outside power source.
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Old 02-16-14, 07:00 PM
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Most of the gas stations around here have a chintzy air machine that gives you 3 minutes of air for 2 or 4 quarters. The tire place's air is only available when they are open.

I got tired of the service station rigmarole and bought myself a Master Flow MF-1050 air pump; $54 at Pep Boys with a coupon. It connects to the car battery (no wimpy cigarette lighter plug) and kicks some serious butt. It will fill a 26X2.25 MTB tire to 60 psi in about 5 seconds and can do 120 psi without breaking a sweat. Very liberating. Highly recommended.
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Old 02-16-14, 07:40 PM
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I need a large volume of air in a short time interval to set up tubeless.

QuickTrip has free air.

I will try the QT again tomorrow morning.
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Old 02-16-14, 09:19 PM
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Originally Posted by robabeatle View Post
I need a large volume of air in a short time interval to set up tubeless.

QuickTrip has free air.

I will try the QT again tomorrow morning.
I probably shouldn`t put ideas in your head, but an old trucker`s trick for setting the bead on tubeless tires was to spray starter fluid (ether) into the tire and throw in a lit match. WHOOMP! Instant inflation.
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Old 02-16-14, 11:16 PM
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Originally Posted by Dan Burkhart View Post
I probably shouldn`t put ideas in your head, but an old trucker`s trick for setting the bead on tubeless tires was to spray starter fluid (ether) into the tire and throw in a lit match. WHOOMP! Instant inflation.
LOL I showed that trick to a mechanic recently. He came over to help fix my wife's car which had a broken shift cable. The tire had gone flat and rolled off of both beads. I was lazy and didn't want to remove the wheel and bring it to a shop. We tried inflating it with air compressor but didn't work. Said to him, "watch this" and sprayed ether in the the tire and threw a match at it. WHOOOMP!! Instant bead seat and inflation.

He was shocked, never saw that before.
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Old 02-17-14, 06:22 AM
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Originally Posted by Dan Burkhart View Post
I probably shouldn`t put ideas in your head, but an old trucker`s trick for setting the bead on tubeless tires was to spray starter fluid (ether) into the tire and throw in a lit match. WHOOMP! Instant inflation.
LOL, I think that I’ll skip that trick.
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Old 02-17-14, 07:05 AM
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Originally Posted by robabeatle View Post
LOL, I think that I’ll skip that trick.
Right, but it sounds like CO2 would work well for you to get the tires set up. Quick blast just like you are needing. Then a regular bike tire pump can be used to keep them up day to day. Also that would be a good idea for carrying on rides. Much more convenient for your jersey pocket than an 7 gal air tank. Purchased online in quantity the CO2 cartridges aren't too expensive.
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Old 02-17-14, 07:07 AM
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I’ve got plenty of CO2 around, haven’t thought of using them.
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Old 02-17-14, 07:35 AM
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I wonder if anyone has tried the either on a small volume tire like a bike! Funt!
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Old 02-17-14, 11:28 AM
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I had never heard of an air tank before. Interesting. I like the used scuba tank idea. I also like the ether/match idea, except how do you throw a match inside a mounted tire?
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Old 02-17-14, 11:43 AM
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Originally Posted by RubeRad View Post
.... I also like the ether/match idea, except how do you throw a match inside a mounted tire?
You don't have to toss the match into the tire, only at the tire where the ether is bleeding out under the bead. OTOH, is Stan's flammable?
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Old 02-17-14, 11:54 AM
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Ah, I get it. That's really cool. Now I want to go tubeless just so I can do that. Homebrew, of course... I don't think latex, slime, antifreeze, or gorilla tape are flammable.
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