diff --git a/maintenance.md b/maintenance.md
index dcf669b..9c0aa7f 100644
--- a/maintenance.md
+++ b/maintenance.md
@@ -20,3 +20,4 @@ Newest entries at the bottom.
 - 2026-09-11: Comms backup tested.
 - 2026-09-14: Water recycling filters replaced.
 - 2026-09-15: Airlock seals checked.
+- 2026-09-15: Water recycling filters replaced.