Good day you all,

I have a CH701sp powered by a Subaru EA-81 and it's running great. After extensive testing, I realized that my 2 x 10 gals fuel tanks (1 per wing) are not enough fuel for my taste.

I 'm running around 6.2 gals/hour which gives me 2.5 hours + 1/2 hour reserve. This is pretty tight for my taste. I would like to ADD 2 x 10gals more fuel tanks (1 each wing). My original tanks have the fuel gauges in them and I dont expect to run the additional tanks on separate gauges. My original tanks have 2 fuel pickups each (one in front, 1 in back) hooked together.

My original tanks are on the first inboard wing bay, the 2 added ones will be in the next bay.

Question is, how do I plumb the 2 tanks together (2 each wing) ?

Is there an anti-return valve that I have to install between the 2 tanks so that when I bank hard the fuel wont go towards the wingtip on the low wing. ?

I know Zenair sells additional fuel tanks for the 701, do they provide drawings on how-to do this ?

Anybody running this setup ???

Thanks for any insight in this matter.



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6.2 gallons an hour??? Holy Molly! I though the EA 81 would do much better than that.
Hi Vance,
It would do better IF I leaned sometime and I did not run it at 90% throttle all the time..
This engine can take it without problem and hold 100% throttle at all time ... I just like to get somewhere faster....

I would say around 5 gals an hour is more conservative if you run at 75% throttle like you should....


Zenair's drawings numbers for this are 7-WTO-1 and 7-WTO-2. They do not connect the tanks together, they use one gascolator for the inboard tank and one for the others, with a three way valve instead of the original one between the gascolators and the engine.

If you connect them together I do not think you need a check valve, as long as you do coordinated turns the fuel will not go to the lower wing. In the standard 2X10 gal setup the tanks are connected together and there is no such problem.

If I remember correctly in Canada you need one fuel gage for each tank, you may want to confirm that if you do the modification.



Hi Francois,

Merci pour les infos. I dont have these pages... Newer plan set I guess... I would rather connect them together in the wing without having to get 2 more fuel lines out to a new valve.



Normand, I have the old style 5.5 gal. tanks from zenith l as outboard aux. tanks, mine are plumbed with a gas tank switching valve [dual tank pick-up style] between the two tanks, and hooked up thru the normally closed port only , I plugged the normally open port, the main tank has a "T" fitting that allows fuel from the outboard to flow into the main or thru to the engine , you only have to energize the valve when the main is half tank or less , since the outboard tank is higher and closer to the spar it flows down and aft. also you dont need gages since the main will read apx 1/2 tank until the aux. is empty , you also dont need complex fuel valves, just right /left /both and two toggle switches...   BOB

Be careful! Extra fuel extra weight. This will limit passenger. Capacity. Just caution to add to check list I learned the hard way. Fly safe.

Hi Normand,

I only have a 601XL but the process should be the same. I added extra tanks in the wings and connected them up with a pump with an internal check valve. I use the original tanks as "main" tanks and just top them up from the "aux" tank. I only have an extra switch for each pump in the cockpit. Works a treat.




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