question, do tanks have a low down outlet aswell as a top opening, as would like to fit 250ltr tank or 400ltr in my transit connect,
Yes mate mine has anyway

next question who is best supplier in terms of price ,delivery
also as above for backpacks and vari flow, on the subject of vari flow can someone explain exactly how and what it does as unsure
I did a DIY and used Gardiners for Tank, microbore, reels, etc. Gaps for RO/DI stuff and Wintecs for pump and varistream
The varistream is the "brain" for the delivery pump so ensures constant flow at the brush regardless of height of pole, number of poles. I'd reccomend it.
Hope this helps
Dave