A fluid reservoir sensing system includes a pair of optical prisms that reflect light when a fluid level is below one of the pair of prisms. The pair of optical prisms includes a low prism usable to sense a low liquid level in the fluid reservoir, and a high prism usable to sense a high liquid level in the fluid reservoir. The fluid reservoir sensing system optionally includes an emitter and a photosensor. The emitter projects light through at least one of the low prism to the low incident surface and the high prism to the high incident surface. The photosensor senses light reflected from the low prism while the liquid is below the low prism. The photosensor also senses light from the high prism while the liquid level is below the high prism.