Yes, you do need a valve for the water.

There are also lifting injectors which suck the water vertically and do not need a valve in the water supply. I have used them on full size engines but have not seen them used on models. Probably because of the higher steam pressures used in full size engines.

Paul.

Garry if you do fit a water shut off valve make sure the bore of the valve doesn't restrict the water flow

H

A lifting injector is "the same as" a non-lifting one, with the exceptions:

– a lifting one needs to work as an "ejector" to lift the water up into the injector; (some full size ones lack this ability) – it means that the overflow needs to be quite large to reduce back-pressure;

– any injector needs to not heat the incoming water too much; in our small injectors, there's a large surface area to water volume as compared to the full-size; having water drip through it keeps it cool, so the steam from the steam cone has a better chance of condensing.

Duncan – on one coal-fired steam crane I used to supervise over here in Canada, one of the volunteers had trouble with the Hancock Inspirator, which should have been self-priming, and lots of steam went out the overflow, which was plumbed BACK into the water tank. Water was low in the boiler; I could not get the injector to lift; the water tank was very warm to the touch; got a fire hose to fill the water tank with cold water, and things were back to normal.

Anyway, just my tuppence on this beautiful day.