thanks for help
i also have vivaro 2900 lwb , which i can position tank behind bulk head only problem i see is the use of side door , i understand by your reply that you run your battery directly into van electric so that battery is kept charged , is there any other electric controls from tank to pump and how is your tank secured to floor
You're quite right about the side door issue. I have a few small bits (minipole, detergent bottle, bits and bobs) between the tank and bulkhead as there is a small gap there. However, I have no problem accessing my other equipment via the back doors. My understanding of the electrics is that the split charge relay allows the leisure battery to draw charge from the van battery only when the van is running. This prevents you getting stranded with a flat battery. When the system is running, the leisure battery uses charge and gradually runs down. I have never had a problem with the leisure battery running too low** during the day though, if doing lots of very short hops, it may be worthwhile running the engine awhile to help charge it.
** I have run it down but not because of the reasons above. With such a system, if you don't let the glowplug light go out before turning the engine, it is possible to pop the fuse near the van battery. This causes the leisure battery NOT to top up its charge from the van battery even when the engine is running. So be aware of this.
The tank appears to be held by two metal straps (or similar) which I believe go around the chassis. I'm not sure but it's an Omnipole system so however they do it is the way it's been done.