Rabbi Chananya Yom Tov Lipa Deutsch, the Helmetzer Rebbe (Helmetzer Rov), was born in 1908 in Szobráncz (Sobrance), Slovakia, into a family of chassidim of the Sighet dynasty, and served before the war as Av Beis Din of Helmetz (Helmec) and its region. After the Holocaust he settled in Williamsburg, where he gave shiurim and became one of the foremost authorities on the laws of mikvaos. From his youth he worked to build and repair mikvaos, and in America he guided the construction of mikvaos in many communities. He authored the multi-volume Taharas Yom Tov and Taharas Yisrael on the laws of mikvaos and purity.
The Rebbe's letters to the Helmetzer Rebbe center on their shared cause: strengthening taharas hamishpacha and building kosher mikvaos. The Rebbe followed up on his work on mikvaos and offered halachic guidance (IK 3189), inquired about the mikvaos in Pottsville and Spring Valley (IK 3662), thanked him for his efforts on a mikveh project (IK 5983), wrote about strengthening mikveh standards in Albany (IK 5855), and advised on advocacy and publicity for mikvaos (IK 6937). He wrote on defending family purity against the concerns raised by mixed beach bathing (IK 2992) and on publishing about the severity of the sin (IK 2642). Several letters join the theme of purity to Torah study and the redemption (IK 5583, 6253, 10418). Halachic exchanges discuss the number of immersions on Erev Shabbos and its sources (IK 7668), and waiting between dairy and meat (IK 7704). The Rebbe also wrote to him on contemplating G-d's greatness before each of the three daily prayers (IK 3705), and sent blessings in Adar (IK 7596).
See also: Marriage – Family purity (taharas hamishpacha) and the mikveh; Halachah and custom – Asking a Rav and halachic questions.