Trapper has posted on this and I think it was the Sears brand. Search Sears water distiller on the VWT forum or under Trapper's posts.

I've never done a good cleaning on my Waterwise. There's some white stuff collected in it but there's no heavy build up. I scour it after every use with one of those green pads. I've also got some of those plastic razor blade I take to it every now and then.

From what I understand the best way to clean them is to run some distilled vinegar through it. You know, that clear white vinegar. I don't know what Sears recommends. The vinegar works good with coffee pots and all so give that a try.

Doc

i just pour some of the white vinegar in the distiller and top of with water and let
stand for 24 hours or so.I get an accumulation of brown gunk and it stained as soon
as i started the distilling.I get rid of maybe 75% of the gunk but thats good enough
for me,i'm sure if you let it sit for days and days it would eventually come out rather clean but haven't tried it.