On Board Water Remote Gauge

[Kingsize24]

If you are worried about the one I originally linked rusting, here is one is stainless steel. https://www.jmesales.com/rochester-...to5Wowl4Q29eY5iV5Y-dI-r2v5lM2gYhoCNsIQAvD_BwE

 

[Worms]

Could you mount the tank on some load sensors and simply use the weight of water as your gauge? Might be simpler than having to build-in additional plumbing for a sight tube or breaching the tank integrity for an in-tank sender unit.

 

[jeegro]

Try these http://www.wemausa.com/sensors/level-FuelWater.shtml