Tender pump and Steam Water Pump In Line?

[doublereefed]

The tender pump and steam powered water pump are in line on one check valve. When the tender pump is used, the water is flowing through the checks on the steam water pump. When the steam water pump is pulling water from the tender it is pulling through the tender pump check valves. Is this legit?

[NP317]

I suggest this is fine.
I plumbed my locos so that the tender hand pump can feed the axle pump, through its check valves, and then into the boiler check valve.
The hand pump outlet "T's" into the tender valve outlet to the axle pump. Closing the tender valve allows the hand pump to feed the boiler through the axle pump.

Before heading onto the tracks, I always use the tender hand pump to verify that I can get water into the boiler this way. Safety backup.
This also fills the water lines through the axle pump. I have never had a failure of the axle pump, in 15 years of operation!
An added benefit: When (not if!) I forget to open the tender water valve to the axle pump, it still draws water through the hand pump checks valves!
Saved from my DUH moments...

So this plumbing method works for my locomotives.
~RN

[James Powell]

I'd rather see a completely separate flow path for each way of getting water into the boiler. In particular, you should have at least 2 completely separate ways for most model boiler codes. This would not count as 2 different ways to me if I was inspecting a boiler. Again, it depends on the code as to the requirement.

That being said, if the steam pump works reliably lifting through the hand pump, and you have an injector or axle pump as well feeding separate, then fill your boots. Our experience was that in 3.5" gauge models, the engine driven pump would have problems (less pumping n) if you did this. It may not matter if you are using a steam driven pump rather than an engine driven pump. It also may not matter as much on a 7.x" engine, as the pump will be quite a bit larger in terms of volume, so will be more able to deal with a fixed loss of volume. (the volume of loss probably wouldn't scale).

James

[doublereefed]

Good point James. The tender pump and steam pump are on one check valve. The injector and axle pump are on a separate check valve. So yes, two different checks, 4 different methods.

[Bill Shields]

The only concern with the steam pump sucking through the hand pump is if you get an air leak in the hand pump around ram....and as a result the steam or axle pumps suck air.

If the hand pump is ALWAYS completely under water, this is not a problem..however if you are low on water in the tender and you have such a leak, you can end up with a problem.

I have one line from the tender to the loco (all pumps) with a manual ball cock in the tender that lets me choose which pumps are supplied (axle & steam or hand).

In my design scenario, this was easier than the extra line from tender to loco.

many different ways to skin a cat(fish).