Hi,
Son Cameron has a 52 plate Peugeot Partner 800 LX 2.0l HDI with a 500l upright tank in the back. He has a fold up ladder and his hose reel and there's no room left.
Also believe he sails very close to max payload with the tank full of water and a full tank of diesel. These models also sit very low when fully laden, inviting trouble.
The other issue is that his poles stick into the cabin between the passenger seat and door making it very difficult for a passenger to get in and out.
My personal opinion agrees with what many have said on this forum - buy the biggest van you can afford. The Transit Connect T220 is similar in payload and size to Cameron's Partner, so I would tend to ignore this van as being too small.
I have a Citroen Relay with a 2 man 650l setup and although a little more expensive to run, I have plenty of space inside. The other advantage is that Cameron and I can work together on some jobs and there is still ample space for 2 hose reels, brushes, poles etc and no fear of exceeding its payload.
IMO the smallest second hand van you might consider is the previous model Citroen Dispatch/Fiat Scudo/Peugeot Expert with a 900kg payload with HDI/JTD engine. A 500l tank will fit in fine, twin sliding doors for easy access but as the cargo area's length is still rather short, your poles will protrude in the drivers cabin. I do believe that a 650l tank in these vans is too heavy when full of water, diesel and all your other kit - although some have this combination. The standard 1.9 normally aspirated diesel engine is very low on power - but as has been stated you don't want to be rushing around with 500l of water on board.
The LWB T230 Transit Connect is a larger van with a 900kg payload but it has a lower roof height than the Dispatch/Scudo/Expert group.
Its all what you think will work for you with your circumstances.
Cameron loves his van and would never go for anything bigger. His model is not speed restricted to 50mph on single carriage ways as bigger van are.
Spruce