Friday, July 18, 2014

How does the mikveh measure up?

Diagram of bor al gabai bor configuration (Lescher 2001:55)
As we conclude a successful excavation at the Pecunies house site, we find ourselves facing many new questions. How did people access the mikveh for ritual immersion? How much water did it contain? How did they fill and drain it? How was the naturally flowing water required to make the mikveh valid collected and how was it added to the rest of the water in the immersion pool? It’s important for us to try and answer these logistical questions in order to understand how the Jewish inhabitants of Puddle Dock constructed the mikveh inside an existing house and what the experience of using it was like.

Hashakah configuration with the opening
 between pools circled in red (Horowitz 2005:70)
 Just in case you don’t recall from previous blog  posts, there are certain requirements that must be  met before the mikveh is considered valid. A few  millennia of debate on the subject have resulted in  several interpretations of the specific requirements,  but a few are generally agreed upon.  The  water in   the immersion pool has to be “kissed” with  naturally flowing water before it’s ready to be used  in purification rituals. Particularly in urban settings,  rainwater is used to accomplish this and it is  collected in a reservoir called a bor. There are  three standard configurations for the location of the  bor.

 The first is called bor al gabai bor or “pit above pit,” wherein the floor of the immersion pool is also the ceiling of the bor and openings in this divider allow for the intermingling of the waters. The second is hashakah or “kissing,” in which the bor is built directly beside the immersion pool and an opening beneath the water line connects the two chambers. The last is zriah or “sowing,” where the opening between the pool and the bor is above the water line and the water used to fill the immersion pool runs through the bor and down into the pool.

Zriah configuration
 (Horowitz 2005:70)
There are also requirements for the volume of water and the ratio of natural flowing water to drawn water. The immersion pool must contain at least 40 se’ahs  of water. A se’ah is a biblical measurement equivalent to 1.93 gallons, so 40 se’ahs equals 77.2 gallons. Additionally, if the immersion pool contains between 66.4 and 264.2 gallons, it can’t have more than 3 log of drawn water (equivalent of .52 gallons), so the remainder must be natural flowing water. If the immersion pool holds more than 264.2 gallons, it can never be invalid no matter how much drawn water is added, as long as it is kissed by natural flowing water.

That’s a whole lot of rules! But now that we know the requirements, we can see how the mikveh at Strawbery Banke measures up (literally). During excavation we managed to uncover the whole floor of the mikveh so we know that it is 5’6” long by 4’ wide and, thanks to the four bricks in course we found along with the lip of one edge of the pool, we know that the side walls of the mikveh were at least 1’6” high. Going by these dimensions, our mikveh held at least 246.51 gallons. It’s very possible that the mikveh had higher walls, but if not, this means that the immersion pool could not have contained more than half a gallon of drawn water.

A close-up plan view of the possible bor adjacent to the
 southern wall of the mikveh with the house foundation visible
An overhead view of the mikveh floor with the
 cistern-like structure to the right
So where was the natural water coming from? While we can’t give a definite answer, there is a small cistern-like structure which we uncovered adjacent to the mikveh’s southern wall. It is likely that this is the bor. Unfortunately, its walls were destroyed along with those of the mikveh, so if this was the reservoir used to collect rainwater, we can no longer see where the opening would have been that allowed for the intermingling of the waters. However, the floor of this structure is made of cement, a common practice in bor construction. The cement was built into the ground and therefore was also considered part of the earth. If rainwater was used, it had to run over a length of earth before it could be considered naturally flowing, so this is a promising find indeed!

More investigation is necessary before we can determine the logistics of mikveh use at the Pecunies house. We will post more findings as research progresses.

 Do you have any theories or ideas about the mikveh or the bor? Feel free to post them below in the comments!


Horowitz, Naomi
2005    A Gathering of Water. Master’s thesis, Department of Architecture, Massachusetts Institute of Technology, Cambridge, MA.

Lesches, Rabbi S.Z.
2001     Understanding Mikvah: An overview of Mikvah construction.


  1. this is very interesting! First time I have read of a family mikveh in northern New England. I hope you will send us follow-ups! Thank you.

    1. Hi Barry! This was actually not a family mikveh, but a community mikveh, built in a house that was purchased by the Hebrew Ladies' Society in 1912, and later owned by Temple Israel. According to Portsmouth City Directories, the Temple Israel cantor lived in the house and likely collected mikveh fees. According to oral histories, there were a few other mikvehs in family homes elsewhere in Portsmouth during the early 20th century, and some people used the ocean as well! Definitely keep reading our blog for future updates!