I'm trying to replace the fill valve of a toilet that's missing some parts and I've run into a snag. I bought a Fluidmaster universal fill valve, and the instructions say that the top of the overflow tube should be at least an inch below a certain level on the new fill valve assembly. But the fill valve seems a bit short, and the overflow tube is higher than allowed. Here's a picture:
It's kind of hard to see because of the angle, but hopefully it's visible how the overflow tube is almost as high as the new fill valve, and certainly higher than the fill valve's "critical level" indicator.
I could cut an inch or two off the top of the tube, but then presumably the water level in the tank will be lower. This is a low-flow toilet so I'm worried that it simply might not flush properly if I let the water level fall. Should I cut the tube anyway and not worry about the lower water level?
If I should just cut the tube, what's the best way to do this? The space inside the tank is really awkward and none of my saws fit. I can get my PVC pipe cutter in there but the tube material is a bendy plastic so it just compresses when the blade hits it.