I just bought a used Softub. I got it all up & running no problem. except it was f-i-l-t-h-y! I bleached & scrubbed, rinsed and filled it up. No leaks, got hot fast, but judging from the looks of the outside when I got it, I'm sure the filter must be totally insanitary. Anyone know how to do this? Where do I find the filter. Where do I buy one? Thanks!