@@AshAndSteam well you fill the boiler with water as needed to keep a safe water level and steam level for operation. There’s no specific answer to your question.
@@AshAndSteam look at it this way: the hotter the fire and harder you work the engine (using more steam) the more water the boiler will use. But if the fire is low (not as hot) and if you’re not working the engine very hard then you won’t use as much steam and water. There are so many different variables to consider. Glad I can help you better understand steam engines and railroading! I enjoy our conversations.
