Vent Line Check Valve?

[Clark in AZ]

Anyone running a check valve on your vent line to prevent fuel from draining back into your header tank, if parked on an uneven surface? I've plumbed in cutoff valves on the supply lines but got to thinking the fuel could drain from the tanks through the vent line. I guess I could put cutoff valves on the vent lines too? Thought a check valve would be easier.

Thoughts?

Thanks,
Clark

[BDA]

I had fuel leak out of downhill tank after parking on a steep beach, so I now use plastic hose crimp locking pliers on uphill fuel line. They are light, and bright orange, with a flag.
I dont have vent lines

[Tralika]

I don't think check valves on the vent lines are going to work. I have a single vent line from my header tank to the right wing tank. I put it in because when running low on fuel in the wing tank, I found that when the fuel port to a fuel line would come uncovered in a nose low pitch attitude (during a descent) when I leveled off the fuel would not start flowing right away. I think it was because I have fuel filters on the fuel lines between the wing tanks and the header tank. I think the fuel filters gave just enough resistance so the air would not flow up the empty fuel line to the wing tank. I have fiberglass tanks so I could see when the wing tank ports were uncovered. I have a fuel gauge on the header tank so I can see when it is not full.

When I first installed my vent line I used clear fuel hose because I wanted to see how the fuel/air behaved in that line. Most of the time that line is full of fuel all the way up to the wing tank. That makes sense because the fuel is trying to find level. The only time that vent line has air in it is when the fuel level in the wing tank is low and the port is uncovered, in a descent. If you put a check valve in that fuel line I think it might trap fuel above the check valve and hold it there preventing the air from flowing up that line to vent the header tank.

You could install gate valves on the vent lines but an easier fix might be to just remove one of the vent lines. One vent works fine. If you park on a slope with one wing down and the fuel valves closed, the single vent line will not be able to transfer any fuel to the low wing tank past the fuel line gate valve.

[danerazz]

If you already have shut offs in the supply lines between the wings and header, and you have one header; remove one vent line. You just need a separate path for air to exit the header and not have to move upstream against the fuel flow.

Then just shut off one of the valves when you park on a slope. Just don’t forget to open it when you preflight. The only thing more embarrassing than running out of gas is running out of gas with a full tank of fuel left.

I think vents are a great idea, I put one on mine, right tank only (because it is on the same side as the header).

If I built another, I would have aluminum tanks, pickups front and rear, running in front and behind the doors respectively. Then to a common manifold in the belly with quick drains at the low points, then on from there. No header.

[Clark in AZ]

Thanks guys! I have two 914 header tanks, one for each wing tank. I also have fuel filter/cutoffs on each tank and I'm running a vent line from each header to it's respective wing tank. I'm installing an Edge Performance Yamaha 300ti engine.

Clark

[Tralika]

If you put a check valve on the outlet of each header tank, rather than the vent line, then fuel will not be able to back flow from one wing tank to the other. That's assuming you do not have a crossover line between the two header tanks.

[danerazz]

If you do not have crossover of the vent lines, and two headers, the headers must come together at some point for feed. If you had a “L-R—BOTH-OFF” selector that would eliminate the problem. No check valves necessary. I agree with Tralika, if you really want check valves, I think the header outlets is the best location.

[Meatball]

I'm so excited this thing is back working!! It couldn't have come at a better time as I've got some questions.

I'm installing the plumbing for the wing tanks and rest of the fuel system and I thought I might need a shutoff on one of them to keep the fuel in respective tanks if on uneven ground. I'm so glad I am not over thinking this and lots of folks have the same thought process.

My question is what kind of shutoff are folks using? Is this a go to Amazon and buy the first ball valve that pops up kind of thing? Any recommendations on one? I'll be running both 100LL and unleaded in my Rotax/Edge 914 so I'm not sure if there is something I need to look for when purchasing.

Thanks so much. Good seeing everyone is still alive and kicking!

[BDA]

Be careful with check valves!!

“Crack presure” is the presure that is required for the fuel to flow through the valve.
Not much presure for gravity flow - I will not use check valves.

[alan]

I have been using a hardware store ball valve for each wing tank, attached to the airframe behind each seat, for almost 16 years with no problems. I fly for one hour and then swap tanks. I always close both valves when the Highlander is parked.

[Tralika]

I also used simple ball valves between the wing tanks and header tank. They work fine. If you go to summitracing.com and do a search for fuel shut off valve you'll find valves from $25 to $225. Something there is sure to work for you. I also have Fram G-12 fuel filters between the fuel valves and header tank. I change them every year during the condition inspection.

[marl59]

I'm currently building a Highlander with the 13 gallon fiberglass wing tanks. They both feed into a 5 gallon Steve Henry header tank. Then from header to dual pumps and dual filters, set up on either/or. I have ball valve shutoffs between the wings and header tank. My fiberglass tanks only had the thick fiberglass build up for a NPT fittings at the lowest point of the tanks. I have to vent the header tank to let the air out as it fills up with fuel. Do any of you have suggestions for how to vent this header into the high point of one of the wing tanks? I'm reluctant to drill a hole high in one of the wing tanks because the fiberglass is pretty thin. Any suggestions? BTW I've installed a Yamaha Apex fuel injected engine in the plane, 160 HP. Thanks in advance!

[SheepdogRD]

One way to strengthen that area of the tank is to rough it up and add layers of fiberglass cloth and resin. Make sure the cloth is well wetted with resin... you don't want to drill and tap and find you made a porous area.

Practice on the inside of a cutoff piece of cowling. Drill and tap your sample.

Here are the reinforcements I did some years ago:

Fiberglass Tank Strengthening 2011-05-30.jpg

[marl59]

Thanks SheepdogRD. The tanks are in the wings so this will be interesting but I've got to go for it.

[SheepdogRD]

If you haven't done fiberglass work, practice first, even if it's just on a piece of cardboard.

Tapping the fiberglass will be a slow, careful process... once the tap starts to bite, go maybe a quarter turn forward, and a half turn back to clear the waste, for lots and lots of cycles. If your fiberglass is well wetted, it should tap very nicely.