Effects of water on dark grains?

[hommebru]

I've been brewing a small while, and have often steeped darker grains for 30mins and then added them to my kits and had no problem. but now i've moved up to all-grain I'm not sure if i should be adding these darker grains to the mash.

the problem is that while i brewed in nottingham, steeping dark grains was fine, no astringent harsh taste, but moving away and continuing brewing, using similar amounts of the same grain i find that i get a much harsher flavour from these grains, which verges on ruining the beer. my process hasn't changed and neither has the grain used so i think it must be to do with the water supply but i'm not smart enough to figure out what it might be.

so now i'm moving into all-grain, i'll be giving basic water treatment a bash and adding some CRS to sort out my mash pH and am working on the rest as i type, but until then would it be best to cold steep these darker grains and then add the liquor (once pasteurised) to the rest of my batch to get a smoother flavour, or would the CRS sort this out for me?

cheers