Minerals in water and Steam operation

Absolutely. There's an entire science devoted to water conditioning for steam boilers. Even today we test for Ph, total dissolved solids (TDS), add oxygen scavengers and anti-foaming chemicals. Back in the day, I understand castor oil was used as an anti-foaming agent.

So when you see a water tower tank on an old steam line, how are they getting the chemicals or oil into the water?

Depends on the road.  Smaller operations would put chemicals into the tender by the dose and just hope that it mixed up well.  Some operations did nothing and had to do lots of boiler cleaning.  Other would have a water treatment shed near the tower so that softening/chemistry could be adjusted as it was added to the tower.

I have no idea how this was handled in the cases of the water "between the rails" scoops like the nyc had. 

When I did some tourist rr stuff we did not have a tower and had to fill the tender with a garden hose.  We had a serious discussion about mounting a softening system under the tender but just never got around to it before things folded up.

In the vast majority of cases, steam locomotive water treatment/conditioning was handled in two ways:

1) At large locomotive terminals, the water was "treated" prior to the filling of the storage tanks. Thus, locomotive tenders received "treated water".

2) At outlying points, whenever water was taken, the Fireman new how many "Nalco Balls" to throw into the tender based on how much water he took, and knowledge of how "bad" the water was at that location.

Railroads that had to operate through larger territories of known "bad water" simply had to do boiler washes more often that the mandated every 30 days.

With current modern era excursion locomotives, which have to take water from local fire hydrants, the water at each hydrant is tested, prior to taking water from that hydrant. Treatment chemicals are then added to either the tender/tenders, or as in the case of SP4449, the treatment chemicals are added directly to the boiler thru use of the injector. Maintaining a fairly constant level of treatment chemicals within the boiler, keep the solid mineral deposits from adhering to the internal steel sheets & tubes, and judicious use of the Fireman's & Engineer's blow-downs then removes the settled-out solids (mud). The worse the water quality, the more often the Engineer & Fireman must use the blow-downs.

Diesels didn't need all that treated water, and that is a BIG reason why they took over so quickly. Alkali was a chronic problem of water supplies in the desert. Untreated or mis-treated water could cause "foaming," when bubbles formed in boiling water and didn't burst. They could carry water through the throttle valve, superheaters, steam chests and cylinders, diluting lubrication and causing all sorts of damage. 

Interesting answers.

What exactly are Nalco Balls?  Similar to water softening pellets?

How about a Nalco packaging plant on your layout.  

I searched and found a little more detail about the "Nalco Balls". See link below.
Ron

http://www.trainorders.com/dis.../read.php?10,1111813

Nalco Chemical Company still exists, headquartered in Naperville, IL. Still in the water treatment business. Interesting to contemplate that they got their start with the huge steam locomotive market.

Nice thread.  Very interesting.  Thanks.

They have a plant near Sugar Land TX, SW of Houston.