Interesting, I would never use tap water. It's doubtful that there are no chemicals in the tap, even in Seattle. But sure, it could be harmless.
I use an RODI that's hooked up to my laundry machine's cold water input is. It makes about 75 gallons in a big stock tank I have, so it's on hand whenever I need it. It takes about 1.5 days to fill it back up with a RODI, so I do that every couple of months. It's easy, since there's a float valve in there so it stops the RODI with pressure when it's full.
To mix, I just get 5 gallons of RODI water, put two scoops of Reef Salt, drop a heater and small powerhead and let it sit for about 30 minutes. While I wait, i just go and use a scraper to get rid of algae, clean the skimmer, and then pull out 5 gallons of water. Then I get the mixed 5 and pour it in. Pretty easy.
It all takes about 30 minutes, sometimes less.
My tank is small, only a Reefer 170, so total water is about 40 gallons, display is closer to 32ish.
