What I do is drain all the water from the 140 gal tank (gravity drains on all sinks) and all fresh and seawater pressurized supply lines. In my case, three sinks with taps, two saltwater deck bibbs and two interior saltwater faucets. The 2 Par pumps are the belt-driven diaphram type and pump themselves dry.
I then disconnect the water lines from the Par pump outlets, open every faucet on the boat and blow all water residue out with an electric compressor. I've also used a nozzle valve attached to a scuba tank, which works equally well.
The water heater is a propane, on-demand type, so no tank. The unit's manifold is drained and drain plug removed prior to blowing out the lines.
All my prior boats had impeller pumps and electric/engine heated hot water tanks. The pink stuff was pumped through after bypassing the drained water heater - left in through-out the winter and drained in the Spring. I really hated using that stuff.
This will be the 4th winterization on this boat, using the compressor method and never had any problems. No chemicals are needed, other than shocking the system with a bleach solution during recommissioning.
True Blue . . .
sold the Nauticat