Join Date: Sep 2013
Location: South Devon
My Motorhome: Bessacarr E725
Thanked 146 Times in 125 Posts
Can you post a photo of the outside of the van where the toilet compartment is?
I expect your toilet flush draws from the main water tank, not a great idea IMHO, but if there is a filler flap outside above the toilet locker that would indicate a separate tank.
Only you know how much flush water you use, it is important to economise where you can.
I'm daft and proud of it.