I would go with
http://www.pplmotorhomes.com/parts/rv-t ... ump-rv.htm Flojet waste macerator pump makes draining your RV tanks easier by eliminating the need for a long cumbersome 3" sewer hose. This waste macerator pump is to be a permanent installation. The Self-priming flexible impeller features a stainless steel wear plate and cutter that reduces particle size to 1/8". An exclusive Run-Dry Protection Device automatically shuts off the pump after approximately 20 seconds of run-dry operation, protecting pump from serious damage. 3" inlet and 1-1/2" hose barb outlet. NOTE: Requires a 1-1/2" discharge hose and 3" inlet hose with clamps. (hoses not included)
This Flojet RV macerator pump grinds up sewer waste enabling you to dump at longer distances and uphill, too! You can even drain your holding tanks at home!
