Just noticed this thread Ronnie
You cannot have your pressure washer above the height of your water tank, Is there a water supply on the roof.
If not you will need to get yourself some additional hoses - we have some 200 metres of hoses for just this purpose.
You don't lose pressure but you have a machine that doesn't suck water - how are you going to do it.
From your point of view - not as straight forward!!!
Rob