I'm passing this observation on in case somebody finds it helpful.

I hate water spots, and use Edwal LFN and distilled water. It works pretty well, best results were using half the dose recommended on the bottle for distilled water. Using distilled water made sense to me since there would be fewer dissolved solids in the final soak that might leave spots. But I still got some. which you can see but which rarely show in a print with a diffusion enlarger.

This weekend I shot two rolls of film that had no intrinsic merit other than being tests. (One was Ilford 100 speed, long expired, the other Tmax 400 long expired.) In one case a meter and a lens on a camera was being tested and the other to seek if I fixed the light leak I mentioned last week in a Graphic roll film back.) So my darkroom processing was a bit more slap dash than usual since the rolls were never going to be printed. I did wash them normally and when it came time to hang them up to dry I figured I wasn't going to waste distilled water on them and I used tap water instead. I added 4 drops of the LFN to one quart of tap water, which the bottle recommendation for tap water. Our tap water isn't particularly hard and we don't have a water softener. I just hung up the rolls with no effort to squeegee them.

I ended up with totally spot free negatives, much to my surprise. They look perfect. Better than I ever got using distilled water. I repeated and got the same result. I guess I'll start using tap water on my sheet film.