Victoria city water, in Fairfield, where,I live has between apx. 12 and 25 ppm (measured with ppm pen)depending on the time of year. Steve, out in Colwood , says he does a little better, so if your Brentwood water from similar sources, it should be close to us.
I take it you don't have a RO/DI set-up. Even with reasonably good ppm tap water, most of the time, it's quality varies with the season. More importantly, at certain times of the year, there is large amount of particulate organic matter ( from winter run-off ?).
RO/DI maybe overkill here, but it is the only way to get consistant high quality water.
Also a basic RO/DI from Aqua-safe is not that expensive (relative to anything else in the hobby) and peace-of-mind is Priceless!!
Good Reefing