Yeah, a valve works. I just have a tiny hole drilled into the side of a union. Same concept though.Use a tee fitting in the RO line leading from the pump. Put a valve at the end of the T ad adjust it so only a little bit of flow comes out when the ago runs.
Place it inside the reservoir at the highest point and in air.
Ato pumps, water goes into sump and a little goes back into the reservoir.
ATO stops, the line will try to siphon but the T will introduce air into the line and break the siphon.
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