Both options of the facelift and the filling up backpack(like KS) have really given me food for thought now. Just need to work out which way to go and brave the change. Whatever decision I make the lifting has to stop as dot want to do my back in at 41 with a baby to look after also. Need to think of all these things now I’m not a spring chicken lol
My advice:
You are struggling using a backpack. Then go to a van mount. Its saves lugging water around in 'bulk'.
Each of us is built differently. KS Cleaning is older than you, but that doesn't mean you should be able to do the job better than he does because you are younger.
Even with a van mount you can still use your backpack for those occasional times.
As regards tanks, everyone will have a different opinion. I fitted 500 liter Wyedale tanks to both the lad's vans. It gave them plenty in reserve. IMHO you will use more water with a van mount than you did using a backpack. My son does.
Setup time with a van mount will probably be longer than using a backpack, but cleaning time is quicker. in our experience on normal everyday houses. When there's a big job to do then the hose reel is far quicker and less tiring.
A good tank frame can be purchased from Purefreedom for a Wydale tank as can the other components.
My suggestion is to get PF to fit the tank as well. They will know exactly where to position the tank on your van so as to not overload either axle.
When your insurance company asks if the tank has been professional fitted you have the receipt to say it has.