The hydramaster one looks just like the cds tank but it looks like it sucks from the far end away from the waste water incoming from your hoses. Probably just a way so they can say the 421 and 427 boxers are dual wand machines. I can see how it could keep water out of a blower but that's about all I see. It says it claims to be better for the seal with 1 inch of area to seal....