Regarding tankage management:
I was referring to general cargo practice rather than large passenger vessels; and by the way I should have said 'fresh water' rather than 'drinking water'. Actual potable (drinking) water costs more and is better placed in the double bottom tanks. There was/is a possibility of contamination in the peaks from weeping rivets started by panting forward and propeller vibration aft.
Non-potable fresh is shipped for boiler feed water and cooling jackets and for general hotel services and sculleries. Potable is piped to health-sensitive outlets such as food prep., bar faucets and service pantries. If supplies were running low sanitizing chemical, usually calcium hypochorite, was routinely carried for converting non-potable to potable. If you are going to ship water as ballast it makes sense to press up your tankage with fresh if available. It goes in the double bottom as well and can usually be transferred between all. The practice varies from company to company, ship to ship – and chief officer to chief officer!
Sanitary water is exclusively salt (unless one is out of drydock or a prolongued spell in port). Seawater was supplied to bathrooms in the older passenger ships and required a special seawater soap – I've never seen it myself. Swimming pools were filled on passage. I've never know 'paid for' fresh water to be used in swimming pools but maybe some cruise ships do it nowadays. They'd need dedicated filtration/sanitization plant.
The ability to quickly longitudinally trim ship can be critical in some operating conditions such as river steaming. Steaming 'by the head' can obviate running flat aground and gives you a second chance.
On intentional 'hogging':– the peak tanks were only supplemental in this, the greater effect being achieved by cargo deadweight. The practice was not illegal per se, the requisite load line criteria being satisfied and (unlike Erik Wood's examples) it did not subtend actual unseaworthiness. The occasion I referred to involved a most prestigious cargo liner company whose ships were in any case built to superior scantlings. And I hasten to add they were as concerned to accommodate important shippers as to garner more freight. Space was at a premium and shippers wanted 'end of month' bills of lading – all to do with bank interest.
I'm rambling again!
To return to the Olympic/Titanic, the peaks may well have been isolated from the fresh water circulating/abstraction system; I have no information. They seem to transcend the tank tops and, as others have pointed out, there were fresh water wing tanks in way of the generator room. But the tank tops were precisely what the name indicates. There was a system of tankage below the plating which does not show up on the general arrangement plan, but all that frame space was not wasted. Gas oil and some 'luboil' also had to be accommodated and, in the case of the Olympic after conversion, much boiler oil.
To my knowledge, there were no on-board distillation or R/O plants in those days and all fresh water had to be shipped prior to sailing.
By the way, what's ships' gender got to do with tankage?
Noel
