I agree with Rambler. I'd just have it pumped and then see where you are. I think a lot of people are reluctant to have it done, primarily because they think it's going to be expensive. Honestly, I can't remember the cost when we had ours done 2 years ago, but it wasn't nearly as expensive as I had feared. I am quite certain it was below $100, but that's all I can remember.
The biggest problem folks experience with septic systems is they forget they're not on county/city sewer. For example, tampons that boast "flushable" should never be flushed, not the applicator and not the tampon itself. When we lived in the city, I didn't think twice about cleaning my hairbrush and flushing the hair. I wouldn't do that on a dare with septic. In other words, don't use your toilets as a garbage can.
We also use Scott tissue. In addition to a roll seeming to last forever, our septic people told us that it was the best choice for septic systems (aside from super expensive toilet paper that was specifically made to break down quickly).
Our septic people also told us that the enzymes and other additives probably weren't of much use except if you were priming a new system or if you somehow managed to kill off all the beneficial bacteria/enzymes (in which case they recommended using a bucket of horse manure to get things going). They said they took an informal poll years ago of homeowners to see who was and was not using the stuff, and they saw absolutely no difference. Of course, that was hardly scientific.
I wouldn't go to the trouble and expense of rerouting my washer and stuff like that unless I determined that I was at serious risk for a problem. The only way of knowing that for sure, though, is to get a septic person in to look and pump. Write down your date of service, how full the tank was and any comments the septic person had. In another few years, you probably won't remember any details.
