Just a quick update in case it helps others but -
What a waste of time this gravel cleaner is, it's made by Pennings or distributed by them, same people who are sending out dodgy lights for the Aldi/Lidl ? tanks that I've read about in another thread here.
I've now on my second as the first broke when putting the thing together. The second has now broken in exactly the same place where the tube is pushed into the main black plastic body. It also stops siphoning after the first bucket full, nothing you do will then get the siphoning started. The thing also leaks from every joint. On a positive note it does manage to vacuum the dirt but overall it's just rubbish.
Although it exempt from being returned I'm going to try on the not fit for purpose point.
Will teach me to ignore advice here where most people said they just use a normal manual siphon, looks like I'll now be getting 1 of these