Thanks so much Snappy! I think I'm going to give it a go and see what I think. We don't have particularly hard water but I've noticed a bit of increased scum. Many of my friends and family have wells too so it might be of help to them.
I use both EDTA and SL in my batches, too, without any problems. I add my SL to my lye water, and I just pour my 39% EDTA solution into my oils after I pour in the lye.