53 Pa. Stat. § 7142
Where claims are to be filed to use, the claimant, at least one month before the claim is filed, shall serve a written notice of his intention to file it unless the amount due is paid. Service of such notice may be made personally on the owner wherever found, but if he cannot be served in the county where the property is situated, such notice may be served on his agent or the party in possession of the property; and if there be no agent or party in possession, it may be posted on the most public part of the property.
The provisions of this section shall not apply if the use-plaintiff is a city, borough, or township to which a municipal claim of a municipal authority organized by a city of the second class, by a county of the second class or by a city of the third class has been assigned or sold, as provided in section four of this act, and the procedure for filing, reviving and enforcing liens for such assigned claim shall be the same as is provided in this act for filing, reviving and enforcing liens based on such use-plaintiff's own municipal claims.
53 P.S. § 7142