Fuel tank, two or three pipes, your preference?

[martin collins 1]

Plumbing up a petrol tank at the moment, advantages or otherwise of using two pipes with a T piece or three pipes with separate tank drain/fill.

[Peter Jenkins]

2 pipes with a Dubro refuelling valve.  Prevents the engine being flooded when filling.

[Dale Bradly]

Since discovering these, im completely sold. seperate fill line,  no stupid brass tubes which rotate in the bung, and easy to see any issues such as interior condition/contaminants (and fuel level!)

[Paul De Tourtoulon]

I still use the old Kavan tanks where I can find one with the red petrol plug, or with the Seagull tanks I replace the plastic tubes with brass and use a ring ( jubilee clip) on the outside of the plug, both with 3 tubes no tees or mechanical stuff to go wrong.

[GrumpyGnome]

Three pipes.

 

Pressurised: fill/unfill, carb, pressure

Unpressurised: fill/unfill, carb, vent

[Manish Chandrayan]

For petrol, my personal preference is to always use the glass tank as shown in Dale Bradly's post. So three lines always. The "T" introduces two extra joints in the plumbing and can also introduce debris in the feed line while filling up. Use a sintered bronze, ceramic or felt clunk and any debris introduced during filling are filtered from the feed line      

[Geoff S]

I use 3 pipes on my petrol-engined models. I to the carb, then 1 for fill and the other for overflow/vent to atmosphere.  I join the vent and fill for transport/storage to seal the tank and avoid spill/smell.  On one occasion I forgot to remove the joining pipe and had a successful flight but there was enough power in the Zenoah 26 Walboro carb fuel pump to squeeze the tank quite a bit - I didn't do it again 🙂

[Andy Stephenson]

I now use these. The normal fill valves rely on having an overflow elsewhere in the system but with these SLEC fillers, have it all in one.

 

[Frank Skilbeck]

5 hours ago, Andy Stephenson said:

I now use these. The normal fill valves rely on having an overflow elsewhere in the system but with these SLEC fillers, have it all in one.

 

Normally you need to leave the vent open when flying with non pressurised tanks, is that possible with these, thanks

[Manish Chandrayan]

Deleted 

Edited September 21, 2023 by Manish Chandrayan

[Caveman]

Andy, I have one of those fittings, it was supplied with an SLEC Funfly kit.

 

I couldn't understand how it was to be used and there were no instruction/clues with the kit. Can you please explain how the plumbing works?

 

Thanks GDB

[Nigel R]

Only glow here, but, 2 pipes preference, every time, if possible - simple is best.

 

 

[Paul De Tourtoulon]

1 hour ago, Nigel R said:

Only glow here, but, 2 pipes preference, every time, if possible - simple is best.

 

 

So how do you fill ?,

[Manish Chandrayan]

15 minutes ago, Paul De Tourtoulon said:

So how do you fill ?,

For two line the only way to fill is through the feed line. Disconnect from carb, fill, reconnect, start the engine and fly if you wish to. 

 

[John Stainforth]

Surely, the preference for two or three tubes depends on the accessibility of the fuel-to-carb tube? If it's easily accessible, two tubes for me; otherwise, three.

Edited September 22, 2023 by John Stainforth
typo

[Peter Jenkins]

You have missed the point I made about using a refuelling valve in an early post.  Something like this - https://www.ebay.co.uk/itm/305072038701?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338749368&toolid=20006&customid=GB_220_305072038701.142451644043~1871005636979-g_Cj0KCQjw9rSoBhCiARIsAFOipll8WC3FGC40u6mERiBDBx_IlI02CGQFgqG8OH43j292_mDBVHF-QTwaAv7rEALw_wcB

 

The valve isolates the pipe to the carb and you can fill or empty the tank.  Once the refuelling probe is removed, the valve reconnects the tank feed to the carb.  There is a failure mode if you  don' use the valve for some time when the rubber sealing grommet inside jams and no fuel enters the carb.  You can see this as the button refuelling probe presses in stays pressed in.  Pressing on the button with a small screwdriver with your thumb and then removing thumb pressure sharply usually frees the valve.

 

You don't need access to the carb to discomnect fuel tubes.  I find them really excellent solutions to refuelling and defuelling.

 

In answer to an earlier comment on vent pipes, the second pipe is the vent pipe and may be connected to the silencer for exhaust pressure or left open to atmospheric pressure.

[Nigel R]

2 hours ago, Paul De Tourtoulon said:

So how do you fill ?,

 

Pull the carb line. Most of my airframes are sport models with all the oily bits hanging out in the breeze and easy access to the carb.

 

If I don't have easy access to the carb, I put a plastic or brass joiner in the fuel line.

 

 

[Paul De Tourtoulon]

4 hours ago, Manish Chandrayan said:

For two line the only way to fill is through the feed line. Disconnect from carb, fill, reconnect, start the engine and fly if you wish to. 

 

Push the oil and dirt accumulated in the fuel line back into the tank, waste not, want not.🤢

[Manish Chandrayan]

1 hour ago, Paul De Tourtoulon said:

Push the oil and dirt accumulated in the fuel line back into the tank, waste not, want not.🤢

Agree. That risk remains 

[Manish Chandrayan]

4 hours ago, Peter Jenkins said:

You have missed the point I made about using a refuelling valve in an early post.  Something like this - https://www.ebay.co.uk/itm/305072038701?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338749368&toolid=20006&customid=GB_220_305072038701.142451644043~1871005636979-g_Cj0KCQjw9rSoBhCiARIsAFOipll8WC3FGC40u6mERiBDBx_IlI02CGQFgqG8OH43j292_mDBVHF-QTwaAv7rEALw_wcB

 

The valve isolates the pipe to the carb and you can fill or empty the tank.  Once the refuelling probe is removed, the valve reconnects the tank feed to the carb.  There is a failure mode if you  don' use the valve for some time when the rubber sealing grommet inside jams and no fuel enters the carb.  You can see this as the button refuelling probe presses in stays pressed in.  Pressing on the button with a small screwdriver with your thumb and then removing thumb pressure sharply usually frees the valve.

 

You don't need access to the carb to discomnect fuel tubes.  I find them really excellent solutions to refuelling and defuelling.

 

In answer to an earlier comment on vent pipes, the second pipe is the vent pipe and may be connected to the silencer for exhaust pressure or left open to atmospheric pressure.

Peter, agree that when refilling with the valve the probe isolates the engine side. But the risk of introducing contamination in the feed line and the tank remains. Plus as mentioned by you the valve o rings fail and cause a headache. I used that valve on a Goldberg Cub (pre internet days and my first time using that valve and did not know the failure point). Wasted an entire evening trying to figure out where the bubbles in the feed line were originating from. Never used another one since then

[Ron Gray]

9 minutes ago, Manish Chandrayan said:

But the risk of introducing contamination in the feed line and the tank remains.

Can’t see how having a 2 way filler valve increase the risk of contamination?

[Martin Harris - Moderator]

Over the years, I’ve seen many dire warnings over the use of these valves.  I have used several and the oldest has now been in use for over 20 years without giving even a hint of trouble.

 

Cleanliness is key with fuel systems - my fuel container is sealed with tubing between its fittings between sessions - connected to the pump at the field and left sealed between uses. The only time the tubing or fittings are open is during fitting or filling.  This also assists in severely limiting air circulation within the container to limit humidity absorption effects. 

[Manish Chandrayan]

1 hour ago, Ron Gray said:

Can’t see how having a 2 way filler valve increase the risk of contamination?

Ron, it's not the valve, it's fueling through the feed pipe (of which the valve is a component). 

This risk is eliminated/drastically reduced when fuelling through a third line and using a sintered/felt clunk as appropriate for petrol or glow. 

That way any FOD introduced while filling remains in the tank and does not get introduced into the feed line. Not until the FOD particles being smaller the clunk filter. But at that size it would not matter much

[Martin Harris - Moderator]

Good point Manish - and why I always have good quality filters on my fuelling system. 

[Peter Jenkins]

Have to say that I've never had a problem with dirt in the tank.  I have a filter between the refuelling valve and the needle valve.  The only problems hsve been caused by a split fuel line or stuck valve.

 

So, I shall continue to use these refuelling valves as they are very useful..