Sand bed binding????

[Aquattro]

There have been reports of vinegar causing this, but it is rare. I don't have that problem and I've been using it for a while. I premix the kalk powder(8 tsp) with about 80ml of vinegar and then add this to my makeup water(5 gal.).
For your problem, I'd say cut back the kalk to what you realistically need, and poke the clumped areas with a stick or something. Your alk also should not drop from adding vinegar (or calcium acetate if premixed). You may want to do a search on Craig Bingman,,he's written tons of stuff about this.