Spring Water

If I use Bottled Spring Water from Costco ... Do I still need to boil it before topping Carboy off with it during Brewing?

I never boiled my top-off water when I was doing extract.

No need to really. However, you may want to do some research and find what the mineral content is for the spring water. Bottled water is mostly a completely unregulated industry so for all you know it could just be tap water in those bottles and your money would be better spent using distilled water. Also, depending on the style you're brewing you want to know the mineral content of the water you are using anyway.

Distilled water?

I have read this is not good to use???

I think you shouldn't use distilled water to brew with. (all the minerals have been removed.) As for top up water, I believe it should be fine.

distilled water - no minerals so can be problematic for all grain mashing.
is ok for top up but. sterilized distilled water is even better as all the bugs have been killed - or you could boil it to kill any contamination.

I ALWAYS use poland springs.. and never boil my top-off water (I do 2 gallonisg boils)...
neve and issue.
tag

Um yeah... I should have added that with distilled you would need to test the PH and also add mineral content to achieve the content you need for the style you want to recreate. With distilled you have a clean palate to create the water you want. With bottled "spring" unless you do the research you don't really know what you have, and it may njot be what you need. But that's just my opinion.

Some of the European bottled spring waters I've seen will list the mineral content on the labels. Not sure if they're accurate but at least something to start with.