I was curious if anyone that fly sparges has tried fashioning an inline hydrometer. I have some scrap polycarbonate tubing that I might take the tap and die set to. The basic premise would be this:
The top is open. There would be two ball valves, one between the mash tun and the housing and one between the housing and the kettle. The former would be opened fully upon sparging, while the latter controls the rate of the drain. The idea being that the height of the wort in the housing would match the liquid level in the mash tun, but would be constantly refreshed.
The added benefit would be that you could see the level in the tun, without opening it, and marking it at the beginning of the sparge would let you know if your rates match.
Am I missing something obvious?