On Fri, 5 Aug 2016 00:29:05 -0700 (PDT), trader_4 wrote:

It doesn't really matter for your purposes if it's by weight or by
volume. If you add water by weight to double the amount or by
volume to double the amount, you're going to wind up with bleach
that is half the strength. There are some negligible differences,
but we're talking household bleach here, right?

I took your advice and simply halved it.
http://i.cubeupload.com/dvzair.jpg

Halving the HASA turned 8 gallons of 12.5% "trade percentage" (sodium
hypochlorite by weight I think?) into 16 gallons of household bleach of
roughly 6% to 10% by volume (I think).