The Mishnah (Shekalim 8:4) states that when a Paroches curtain becomes contaminated with tumah it must be immersed in order to purify it. If the source of tumah was an av hatumah [primary source] then the curtain must be removed from the Temple immediately, immersed, and then hung out to dry upon the Temple Mount before being returned to its place. Outside the Temple Mount there were many mikvaos for people to use prior to entering the Temple, and certainly it would have been possible to construct a mikveh large enough to contain the Paroches curtain. As described in the previous post such a mikveh would ideally be a shallow pool measuring just over 20x40 amos in length and width. Three hundred Kohanim would hold the curtain taut around its perimeter as they lowered it into the water.
The Mishnah also states that when the curtain was contaminated with a vlad hatumah [secondary source] it did not need to be removed from the Temple but could be immersed in the Courtyard itself. Within the Courtyard it seems highly unlikely that they had a dedicated mikveh that measured 20x40 amos. At least, I have never seen any such mikveh mentioned in the sources. The two approaches I have seen to explain this Mishnah write that the immersion was done either in the mikveh of the Kohen Gadol located on top of the Parvah Chamber (Meleches Shlomo) or in the Sea of Solomon [a very large copper basin that functioned as a mikveh] (Tiferes Yisrael).
It is hard to imagine how they fit the Paroches into the Parvah mikveh. Although the Mishnah never states a size for this mikveh, from the Gemara (Pesachim 109b) we know that it was no larger than the minimum size of 1x1x3 amos, as follows: The Gemara suggests that the tabletop of the Shulchan [Golden Table of Showbread] — which measured 1x2 amos — must have been made of two pieces that could be taken apart. This is in order to have the Shulchan fit into the Courtyard mikveh (i.e., the Parvah mikveh) for immersion (Rashbam), because a utensil that is exactly one amah wide cannot fit into a mikveh that is exactly one amah wide. [The tabletop could not have been inserted diagonally because it was too thick.] Thus, the Parvah mikveh was exactly 1x1x3 amos, surely too small to be able to fit a curtain measuring 20x40 amos and one handbreadth thick!
The Sea of Solomon held a volume of water equal to 150 standard mikvaos (Pesachim loc. cit.). With some careful and gentle folding, it should be possible to fit the large curtains into it. So while this solution would have worked for the First Temple, what about during the Second Temple era when there was no Sea (see Tos. Yom Tov to Middos 5:4)?
I can see two possible ways to immerse the large curtains in the Courtyard of the Second Temple. Both use the exact same principle but differ in their practicality. The first way is to use the Courtyard itself as the mikveh. By blocking the channel of water that flowed out of the Water Gate it would cause the Courtyard to flood (as was done each year to clean up after the Pesach offerings were brought). The water would have the halachic status of a mikveh (a maayan, to be exact) because it came from, and was connected to, the Eitam spring. Once the water was deep enough (just over a handbreadth) the curtain could be immersed right on the floor.
|Water Sources in the Temple. Water flows in from the Eitam spring and out the Water Gate.|