Not a problem. It helps that I have some training in plumbing systems. The only major difference between a ship and anything you find on land is that a ship has to distill it's own fresh water from the sea. The general operating principles are the same.
If you wish to read a good general article on the Olympic class that was written at the time, you might try clicking on THE WHITE STAR LINER "TITANIC" from the British Journal "Engineering" I didn't notice anything specific on the evaporators, but it might help to answer some other questions you may have.
I believe the distilling machinery was used primarily to augment fresh water for the feedwater system of the steam plant. Fresh water for the steam plant was carried in tanks in the inner bottom under the reciprocating and turbine engine rooms with a total capacity of 1000 tons. Above the double bottom, the Titanic held a total of 962 tons of fresh water in 6 tanks along the sides of the dynamo engines and in a tank abaft bulkhead C in No. 3 hold. See: https://www.encyclopedia-titanica.org/articles/halpern_deck.pdf.
The drinking water was brought on board by a water tender or from the dock. Though the ships of the period were capable of distilling their own drinking water, it was generally avoided because of the amount of fuel required. As for feed make-up water Samuel's post applies.
Michael: The only original drawing I found of the inner bottom was that of the britannic that appears on p. 206 of Simon Mills' book "Hostage to Fortune." You can see that the tank layout under the tank top was the same as what I show in Fig. 2 of my article on the Titanic that I referenced. What was different on the Britannic was the addition of 2 more fresh water tanks above the tank top aft of the first dynamo engine room. The 4 electric dynamo engines on the Britannic were divided into two separate compartments by the addition of a WT bulkhead, with two dynamos in the first compartment and two in the second. There were two fresh water tanks on each side of both these compartments on the Britannic, and the FW tank aft of bulkhead C in hold 3 was apparently eliminated.
See att. figures for comparison to Titanic.
Interesting stuff there, Sam. Learn something new every day! I wonder...was the Olympic ever modified with the additional tankage? It would make sense if what was originally there was considered slightly inadaquate.
The person to ask about modifications to Olympic would be Mark Chirnside. Did you notice that on the Britannic they added a 16th watertight bulkhead above the double bottom, dividing the ship into 17 major compartments. This was the bulkhead between the two electric dynamo rooms.