231 Pa. Code § 1026 : RULES OF CIVIL PROCEDURE — GENERAL — ACTIONS — CIVIL ACTION —PLEADINGS — Time for Filing. Notice to Plead

(a) Except as provided by Rule 1042.4 or by subdivision (b) of this rule, every pleading subsequent to the complaint shall be filed within twenty days after service of the preceding pleading, but no pleading need be filed unless the preceding pleading contains a notice to defend or is endorsed with a notice to plead.
(b) A defendant served outside the United States shall have sixty days from service of the complaint within which to plead.

231 Pa. Code § 1026