How many books are in the The Plumber's Mate series?

There are 5 books in the The Plumber's Mate series.

When will the next book in the The Plumber's Mate series be released?

The The Plumber's Mate series does not have a new book coming out soon. The latest book, Lock Nut (Book 5), was published in May 2018.

The first book in the The Plumber's Mate series, Pressure Head, was published in August 2013.