I'm with the earlier posters who advised distilled or filtered water, at least for the final rinse. Before I switched to filtered my negatives were routinely emerging covered in crud. I used a film squeegee for a while which greatly improved things but increased the risk of scratches on the still soft emulsion. Filtered water completely cured the problem of dirty negatives. If using Photo Flo or similar in the final rinse, I'd use half the recommended dilution. You might also want to pick up a small bottle of Rodinal developer. It keeps for ages - years in fact - and gives lovely negs when used at a very economical 1+50.