I have built my own homebrew version of this thingy: http://www.bestvaluevacs.com/5gvac.html

I bought a 25mm thick piece of perspex, drilled and tapped holes in it, milled a 3mm deep concentric depression and poured silicone rubber in it. Fitted the perspex with taps and gauge. That goes on top of a 30 liter aluminium soup kettle. A silicone heating ribbon with control unit, fibre-glass insulation and a deep-vacuum diaphragm pump completes it.
With this I can create an approx 50-70 mbar vaccuum and heat the whole thing to 70 C. That dries all filament extremely well in a matter of hours.

It will cost you money to get the whole thing together, though. But once you have one, it is a blessing. The vaccuum also does wonders for de-gassing epoxy resins and silicone rubbers before pouring.

Other people have reported success with drying in ovens (I tried that once and the reel melted, ruining three spools of filament) and on central heating radiators. I have tried both, but my experience is that nothing beats a vaccuum oven setup.

If you mail me a 20 cm or so of your filament, I can extrude it before and after vacuum drying and show you the pics. That will prove the water absorbtion issue one way or the other.