I have been using this one for a few weeks now, great bit of kit so far, mines the v 17 one, and I've attached my lance to ithttp://www.mobiwasher.co.uk/?gclid=CKLevJvHjbECFU4lfAodl1uvNgStu
Just a idea,sometimes when i want to lay alot of pre spray fast,i put some pre spray in a bucket,then put the two hoses from my chemical feed.Open the valve all the way.Connect my spray lance for washing my van to solution hose and spray.Then change back to normal solution.