Weird Alkalinity numbers

[MattGuk]

OK, so a while back I posted a tread on here about using Carbonate Reducing Solution to help deal with my high Alkalinity, which was around the 189 mark as Hc03.
Don't know if this is possible, but last week when checking my Alkalinity again, I ended with 70ppm as HC03 before even adding anything.
Now, I get that with the hot weather we had over here may contribute to this, as people would have been using much more hence the water isn't in the reservoir for as long, but this low?
I used the Salifert KH kit both times.
Just goes to show that even having water tested, it really is only accurate at the time of testing.

 

[Vale71]

My untreated water TDS can drop by as much as 50% when it rains heavily in a matter of 24/48 hours and the municipal water supply comes from a deep artesian well and not an open reservoir...

 

[rsquared]

Some places (including where I'm at) use different water sources depending on the time of year as well. I've heard some people get around this by getting a water test for each season.

I eventually decided going with RO was easier for me, but it does mean I have to make sure I've got a couple 5 gallon jugs filled at the grocery store before every brew day.

 

[MattGuk]

Buying RO over here in UK is not easy, when it is available in places like aquarium centres it is expensive, maybe I will buy an RO system and build the water myself.

 

[rsquared]

Interesting, I didn't realize it was so hard to find there. You can't walk into a grocery store here without passing a refill machine... I've started considering a home system for myself as well though, just so I've always got water available.