We used vinegar to clean ours when we got the MH. It seemed to do a good job. To do it right, when flushing you need one of those plastic wands with a 90 deg tip on the end to send the water to the ends of the tank so the **** gets flushed out.
Secondly - don't drain the vinegar out onto your grass..............
Third - we bought a two filter system, to use with the filter in the MH giving us three filters. Even in the southwest we don't have a problem calcium, or anything leaving spots on anything anymore. It uses a std sediment filter, a charcoal filter and at the moment I don't remember what the third filter is.
Bill