DON'T use your wet-dry vac to pick up sewage! It will stink for a really long time afterwards! Ask me how I know! What I did the next time was buy a white plastic bucket with lid, and a short piece of 1" clear hose from Home Depot. Punch two holes in the lid, one for the vacuum hose, and one for the clear hose. Leave the holes a little small and just force the hoses in for tight fit. Now you can use the vacuum and collect everything in the bucket. If you need to empty it more than once it is a lot easier carrying the bucket than trying to dump the vac.
You guys are worrying about a lousy little head. I work in the waste water industry. You should try taking apart 8" pipe and pumps that are filled with sewage!
Gary H. Lucas