I winterized the Mary Joan yesterday. Took advantage of this task to install a five foot loop of flexible tubing between the water pump and the factory installed water piping to try and reduce the very loud "hammering" of the system.

I cut the 1/2" ID tubing about 8 inches from the outlet of the pump. I purchased high pressure reinforced 1/2" ID water tubing and two 1/2" to 1/2" nipples at my local hardware store. Using the two nipples and stainless steel hose clamps, I spliced the five foot section into the cut ends of the line I had cut. It helps to heat the tubing in order to insert the nipples into the tubing (a pot of boiling water worked well).

This simple modification greatly reduced the hammering sound from the water pump.

As for the winterizing, I followed the Airstream manual almost exactly except that I drained the hot water tank by removing the drain plug (the heating element in my case). After completing the recommended procedure, and with the drain cocks closed, I used a length of plastic tubing inserted into the intake side of the water pump (I wrapped duct tape around the tubing in order to get a reasonable seal around the tubing) and drew RV antifreeze from the container and, with the hot water tank bypassed,  pumped it through all of the plumbing by sequentially opening all water outlets; galley, shower, lavatory sink, toilet and toilet flush hose. Finally, I opened the drain cocks to allow a small amount of anti-freeze to drain in order to protect the valves.