Reference for Makhshirin 2:5
עִיר שֶׁיִּשְׂרָאֵל וְנָכְרִים דָּרִים בָּהּ וְהָיָה בָהּ מֶרְחָץ מַרְחֶצֶת בְּשַׁבָּת, אִם רֹב נָכְרִים, רוֹחֵץ מִיָּד. וְאִם רֹב יִשְׂרָאֵל, יַמְתִּין כְּדֵי שֶׁיֵּחַמּוּ הַחַמִּין. מֶחֱצָה לְמֶחֱצָה, יַמְתִּין כְּדֵי שֶׁיֵּחַמּוּ הַחַמִּין. רַבִּי יְהוּדָה אוֹמֵר, בְּאַמְבָּטִי קְטַנָּה, אִם יֶשׁ בָּהּ רָשׁוּת, רוֹחֵץ בָּהּ מִיָּד:
[If there is] a city where Jews and gentiles live and there is a bathhouse in it that is used on Shabbat: [If] most [of the residents] are gentiles one may bathe there immediately [after Shabbat]; and if the majority are Jews one must wait [the time it takes for] the water to be heated; [and if] it is half and half one must wait [the time it takes for] the water to be heated. Rabbi Yehudah says: One may bathe in a small bathhouse immediately if there are officials [who use it].