Anders, I don't know about Wasabi's, but there are several different types over here; some are one big tank divided into different compartments while others are just two or more tanks. For a small mobile home, I had one system installed that's two 400 gallon concrete tanks (code only required two 300 gallon tanks), although two 500-800 gallon tanks are more the "norm" in my area. And the residue is not collected on any regular basis by any governmental agency. There are a number of septic service companies listed in the phone book (with widely varying prices) and it's up to the property owner to contact one of them to "pump" the tanks when needed. Some property owners have it done on a regular basis; very few on an annual basis, some on a two year basis, but most folks around here only have it done when they have a problem (not the best way, I guess). The installer of the 400 gallon tanks that I mentioned said they shouldn't need anything for 7 to 10 years unless too much grease went into the system or bleach or something like that that killed the microbes that digest the solids. I know my brother-in-law and his wife lived in the area for nearly 10 years and never had anything done to theirs. I believe in some areas of the country, they have local laws requiring periodic pumping of septic systems.