Auxillary fuel tank replacement GU

Hi Stevo,
I had a 180 litre replacement auxilliary tank on Tuesday through a ARB associate. I filled it up to the filler neck with 172 litres. Not happy as I had specifically asked about USEABLE litres when researching which tank to install. After making enquiries yesterday with Out of Town in Newcastle who manufacture the tank I finally got onto THE MAN who either designed the tank or had access to the CAD drawings and was able to assure me on the questions I had. It turns out the design shows 186 litres total volume that should be able to give 180 useable, the problem apprears to be expelling the air.
Suffice to say contact the manufacturer direct not his reseller when you have questions of design.
Regards
Ian

Stevo mine sits about 50mm lower then chassis rail can't tell you what brand it is as the previous owner fitted the tank. Size would be about 80litres although hard to tell because gauge reads empty when you have only use 30litres.

Cheers Dave

Don't know anything about these tanks in particular, but I used to have an old F100 Ambulance with twin fuel tanks in it (needed 'em too!)

Had a similar air lock problem requiring driving up on a wooden block to tilt the filler upwards. The Mobil in North Perth had a sloping driveway which had the same effect. Made a big difference to the fuel payload.

Struth,
I've always thought those aftermarket replacement sub-tanks were supposed to sit above the lower limit of the chassis rails. I'm glad I haven't gone ahead and bought one; the last thing I want is a tank which hangs below the chassis...first rock shelf and the weight of the truck ends up on the tank, perhaps?
As for the therm "usable", I've always worked on the 10% rule.....IE: if a tank is supposed to hold 100 litres, don't bank on getting anymore than 90 out of it. There has to be a reasonable amount which can't be accessed by the pick-up system; it may not be a full 10%, but it's better to err on the side of caution IMHO.
Cya