I'm assuming that after 4 days, you've already replaced the hoses....If not, I just replaced mine with neoprene. It's a pretty small ID, prolly 3/32" or so.
I can't remember. The guy at the parts store knew though.

It just slips on. I suppose though, if you suspect a vacuum problem, you might want to use a clamp, but I don't think you need to. It seals pretty well. and the fitting on top, that it slips on to, is plastic and would prolly crack if you use a clamp.