There isn’t a lot of science to figuring out drain line problems. If it won’t drain, there is something in the way. It’s amazing what kids will try to flush.
Every home should probably have a toilet auger. For those times when the plunger doesn’t do the job it will reach through the toilet and clear any obstruction within three feet. It has a protective plastic sleeve that prevents it from damaging the toilet enamel.
You may also find it useful to have a 15′ to 25′ foot snake of the kind that comes rolled up in its own little drum. You push the tip as far down as you can and then work more in by rotating the drum. These two snakes should take care of most problems with stopped or slow lines.
You can buy bigger, longer, snakes, but I am not sure it is worth it for the mobile home occupant. Unlike at site built house, all your drain lines are visible and access able under the house. If you have plunged and snaked the first few feet of drain line from inside the house without fixing the problem, it will probably be visible from underneath. I have seen cases where the lines were not properly supported and solids gradually accumulated at a low point. There can also be problems resulting from dripping faucets in cold weather. But where I live, I didn’t have to deal with that.
