Hi Sam,
In spite of the testimony of Beesley, Barrett and Beauchamp, I suspect that the main condensers and circulating pumps had probably been shut down earlier. As you note, the main condensers were really only required to operate the main engines as there was an auxiliary condenser plant in the starboard side of the reciprocating engine room, complete with it's own circulating pump and air pump, designed to handle the full load of all of the ship's auxiliaries. Between this, and the auxiliary surface heater providing preheating of the return feedwater, on the surface of things there would seem to be no need for the main condenser plant.
Personally, I suspect that the main condensing plant was probably shut down not very long after the engine room became fully aware of the true nature of the situation that they were facing. The main circulating pumps were the biggest users of steam in the main engine rooms, second only to the main engines themselves. Once it became clear that ship wasn't going anywhere, these pumps had no secondary purpose other than clearing water from the bilges of the engine rooms -- not a factor that night. Given how drastically steam production was cut between loss of two boiler rooms and the drawing of fires and blowing off of steam in others, I have to ask myself why wouldn't Chief Bell have shut down these redundant systems? This would seem to be the logical thing to do, if for no other reason than to conserve the steam still being produced for the pumps connected to the bilge system, which were no doubt being run at peak capacity, and for the main electric plant, which I'm sure was also seeing an increase in load as lights were being turned on all over the ship.
Another thing that had me suspecting that the main condensers had been shut down by this time has to do with the complete absence of any similar stories from the occupants of boat No.14 (or from those in 12 and 16) on the port side, which were all lowered between 1:15 and 1:25 (per Behe, et. al.), not long before Nos. 13 and 15. Had boat No.14 encountered anything like the stream of water that those in No.13 were threatened by, I'm sure that somebody in that boat would have become alarmed enough to have said something about it during the launching, or in accounts written after the fact.
Yet, the fact remains that boat 13 did encounter a large stream of water as they reached the surface of the sea, so this water came from someplace. What I suspect is this: the large stream of water that threatened this boat and had these men so concerned might not have been from the condenser discharge, but from one of the pump discharges just forward of this. One of these was a shared discharge was from the two large duplex pumps in the forward starboard side of the turbine engine room -- two of the numerous pumps that had distribution boxes which allowed connection to multiple discharge and suction sources, including the bilge mains. Though not nearly as large as the main condenser discharge, this was from a pipe of about 8-inch inside diameter attached to a valve and chest with an with an outlet of approximately 10 to 12 inches, and had with two pumps of at least 150-ton/hr capacity connected to it. Among other things, these pumps and their counterparts on the port side appear to be set up to perform a variety of tasks, from bilge pumping to circulating the two oil coolers in the turbine engine room and the fresh water distillers up in the didcharge recess. Even though this wouldn't have been nearly as impressive as the huge waterfall that normally issued from each of the main condenser discharges, a jet of water a that is about foot in diameter at it's source, spreading out to perhaps twice that as it fell, would certainly be at once both awe-inspiring and terrifying to those being lowered through the darkness into it's path. To anybody but one of the ship's engineers, I'm sure that this could have easily been mistaken as being the discharge from the condenser.
Now, I could easily be wrong on all of this. For one thing, the exhaust line from the generators had connections not only to the surface feed heater and the auxiliary condenser -- there was also a connection through a large valve to the after end of the starboard main condenser. Could they have operated the starboard condenser alone, with one or both starboard circulating pumps running at reduced speed? Perhaps; a bit like using a shotgun to kill flies. But, perhaps... Without knowing the conditions under which this connection was designed to be used, it's not possible for me to evaluate my suspicions based on this information alone. What I wouldn't give for a look at the engine room operations manual for one of these ships!...
Regards,
Scott Andrews