Hissing Noise Region of Fuel Tank

[YoungBob]

Have just taken delivery of my T32 Kombi LWB 199, which is generally great, however there is a hissing noise from the region of the fuel tank. It starts on starting the engine and is audible from inside, loudest around the bench seat. Stepping outside it is much louder and appears to be coming from under the van, louder on the left, under the sliding door. After turning off the engine, it continues for a couple of seconds.
I have seen some threads about this but still cannot work out if it is normal. Is this something that is present in all the newer vans with my engine (my T5 never had it), or do some people out there have similar vans without this noise?

 

[RedUn]

It might be doing a regen? They are definitely noisier when doing that

 

[Loz]

My fuel pump can be heard in that location but not from the inside.

 

[Broadside]

Do you have an aux water heater fitted? If you do then it will fire up when the ambient temp is under 5c and can make a hissing sound but I wouldn’t say it is very loud, it does continue for up to a minute after switching the van off. It is located just behind the near side front wheel arch. If you’ve got it factory fitted there will be a Webasto sticker on the drivers door.

 

[Dellmassive]

Fuel pump. . . .

 

[YoungBob]

Thank you for your replies. I don't have an aux water heater.

I think it must be the fuel pump and "normal". If you cannot hear it in the van, do you have underfloor sound deadening or just sides?