On the safe-t-alert question I had the same questions but couldn't get answers on sizes so I took out the old one and got replacement the same size to put back in existing hole. And I actually read the info sheet on new one, which said to the effect...good for five years from date of manufacture listed on back. Which was already 1 1/2 years old when I bought it "new". Which means replace date is not purchase date. Maybe you'll get lucky or ask for a "fresh" one.
On solar sewer pipe vent question. IMO anything solar that is $25.00 can't be that good.
2003 Majestic 23P... Northwest travel machine
2013 Arctic Fox 25W... Wife "doll house" for longer snowbird trips
2001 "The Mighty Dodge"... tow vehicle for "doll house"