The Titanic had specially designed distallation machinary called evaporators for this sort of thing. There were three of them of the Quiggans type which were manufactured by The Liverpool Engineering & Condenser Co. and had a capacity of 60 tons each per day.
Which pumps? There were tanks for potable water in the double bottom, however, there was also a potable water tank in a deckhouse on the Boat deck which was used to keep pressure in the system. The requisite pumps would have kept this tank supplied. Gravity did the rest.
There is some discussion of the construction of the evaporators in "The Shipbuilder", but they don't go into great detail. For the most part, these publications tend to discuss the unique aspects of the ships and their machinery and omit what was common knowledge for their audience.
The evaporators were basically big heat exchangers. There was an array of steam tubes in contact with the salt "feed" water. The steam was at relatively high pressure and thus had a temperature well above the boiling point of salt water. The feed water would flash to steam and was then cooled so that it would condense, producing distilled water and leaving the salt and other minerals behind in the feed water. A certain amount of the feed water was dumped overboard, keeping the salt in the evaporator from building up too much. I don't believe that the source of the steam for the evaporators is mentioned. A quick scan of the engine room drawing from "Engineering" indicates that it came from an auxiliary steam line on the starboard side, so it was probably 100psi or better, straight from the boilers.
Note that the evaporators made distilled water, which is not the best for drinking. Titanic carried a lot of fresh water in tanks and it was used as the primary source of potable water. The main purpose of the evaporators was to replace boiler feed water that was lost during operation.
Am I right in thinking that Capt. Smith's bath had four taps: two for hot & cold fresh water and two similar taps for salt water? I'd be interested in knowing if this arrangement was duplicated in other areas of the ship.
I think only the private bathrooms in 1st Class suites had fresh water taps, and these were connected to a shower head rather than the bath itself, which had the usual sea water supply as in the communal bathrooms. Maybe that was the same arrangement that Smith had? Passengers using the standard bathrooms were provided with a jug of fresh water for final rinsing.
The fresh water used for drinking was filled from the side of the hull from the wharf or a water tender. It was stored in the six tanks abeam the electric generating compartment. This was specifically for consumption. Washing water was stowed in the double bottom in specific tanks. The fresh drinking water and washing water was pumped from below to the elevated boat deck tanks where it was stowed to allow it to feed the main by gravity (this is like a village water tower). Though salt water could be distilled on Titanic, it was not cost effective, and done in emergencies only. If the distilled water was used for consumption, it would have to be passed through an aeration filter to bring it to life. These devices were on Titanic and liners of the era, but used as a back up. Otherwise the distillers etc., were used for making boiler feed water which was also loaded from a tender, and only manufactured if needed.
The fresh water that came out of the first class lavatory basins and private bath shower heads, Smiths shower etc. was of this washing water quality (if you will) and was not intended to be consumed. Water that was intended to be consumed was brought to the room by a steward, and was supplied to the galleys and pantries. The fresh drinking water passed through a Pasteur filter at some point in its travel to the tap. Whether this was done through a filter in the engine room, or filters at the service points (most likely) I am unsure about. There were water coolers on this ship in areas also. When one sees a glass flask next to a fold down or marble lavatory basin with drinking glasses below it etc., that drinking water did not come from the sink (or it should not have). It was brought to the room by a steward/ess.
The hot salt water used for baths was of course pumped from the main condenser discharge where it was already pre-heated, and sent to storage tanks were it was maintained to the prescribed temperature. The cold salt water from bathing and the pool came right from the ocean.
Hot washing water was maintained in 'tween deck tanks and rose up to the underside of the service giving immediate hot water upon opening the tap. The overflow from these "rising mains" returned back into the system in most cases.
Water used for flushing the sanitary system, toilets and urinals, as well as those systems used for wash deck purposes and fire mains came right form the ocean, but unlike the 1911 Olympic and many other ships, was not stowed in a large tank on the Boat Deck. The water pressure was maintained in the mains by direct pumping. Olympic was converted to this system, removing the sanitary water tank in 1912-13 to make room for the engineer's smoke room, while Titanic and Britannic were built with this feature from the beginning.
The swimming pool, or bath, whatever one wants to call it, was actually a large bath tub. It had both hot and cold salt water mains going to it from the ship's corresponding service mains. It should be noted that the drain and overflow from the pool went into the No. 5 Stb wing tank, which seems to have been the receptacle from other overflows also.
Sorry for any spelling mistakes - in a hurry as usual
Just to clarify: often, the term "distiller" gets used interchangeably with "evaporator", but these were in fact two different devices. The three evaporators used on the Titanic desalinated sea water by distillation, which is what tends to cause the confusion in nomenclature. The fresh water distillers, on the other hand, were basically small condensers with a charcoal filter in their bases, and an open atmospheric connection which promoted aeration of the condensate being collected within. There were two of these devices, both located against the WTB in the forward portion of the starboard condenser discharge recess.
Condensate obtained from evaporators is ideal for make-up boiler feed purposes, being almost completely deaerated. (Oxygen and other atmospheric gases dissolved in feed water is the main culprit in corrosion of the interior surfaces of boilers, and in the premature failure of furnaces and tubes in Scotch boilers.) However, for the same reason, even though the raw condensate from an evaporator is safe to consume, it is completely unpalatable as drinking water, having vile taste. To create drinkable water, the aeration and charcoal filtering provided by the distillers -- but most especially the aeration -- are necessary to producing palatable fresh water for drinking purposes.
On the night of the 14th, Lightoller told the carpenter to look after the fresh water tanks, as they might be in danger of freezing. What was the carpenter supposed to do? Was there a method of heating the tanks, such as steam pipes running through them?
According to Bruce Beveridge, Lightoller was not speaking of the main fresh water tanks themselves, but the fill pipes on the aft end of No. 3 funnel feeding the gravity tanks. If the weather was cold enough, they had to bleed the water out and turn off the pump to keep the water from freezing in them. There was enough water in the gravity tanks topside to keep the supply through the night. During the day, they would put the pumps back on line to replenish the gravity tanks.