Blowing out your lines from the city water inlet will not blow out your water pump. What you could do, after you blow, is to get a couple hoses with 1/2 inch threads and attach one to each side of the water pump only. Then pump some pink stuff through the pump and catch it in a bucket. Shouldn't take more than a glass full to do it. Then in the Spring, get a bucket of fresh water and pump it through the pump only and catch it in the bucket again. This will clean out the pump from any residue pink-stuff. Then reattach both hoses to the pump for your camper.