I think a wet dry shop vac is a good thing to have. My experience is perhaps typical. One day in my house I was feeling well in control as the fellow worked on installing a new furnace in the garage. True it was expensive, and I wasn't sure it would be necessary as we only need heat out here in the near maritime desert like chapparal once in a while. But when it does get cold, it gets cold. Oldest son was taking a shower downstairs, middle son was reading or something, when suddenly! Yes, suddenly, oldest son came out the bathroom yelling, Dad! the toilet is overflowing! Not to worry; the plunger was at the ready. Except this was no normal toilet overflowing. The tub was also overflowing. Everything was overflowing. It made no sense. How could this be? It turned out, to make a long story short, that there was, or must have been a clog inbetween the septic tank and the house, and that, uh, stuff from the drains were proceeding out toward the clog and then back out the toilet et al. downstairs. I felt a lot of things, but mostly I wanted to cry. I was seized by a deep feeling of immobility not unlike panic. "Grab towels!" I yelled, and we did. "Shut off the water!" I yelled, and we did. This was just the beginning of the long, stinky mess. The fellow working on the furnace dropped his tools and said "You have a wet dry out here. Do you want me to use it?" Yes, yes, I said. Such was a terrible mess rendered somewhat less terrible. The saga would continue through two more notable stages, but let me just confide, when they say you should evacuate your septic tank every three or four years, that's what they mean, or maybe five, but not in any event eleven and a half. You can't use a wet dry vac to evacute your septic tank but it will come in handy if you don't. It's also good for wood shavings.