I've been filtering my water using Brita and other similar products, but recently realized that this did not filter out the calcium carbonate.
What kind of products should I buy to soften the water coming out of my sink?

Get an RO. Then remineralize. I tried some half measures but the water is too hard in la for most normal softener/filter solutions.

Sorry. What is an RO?
Is it reverse osmosis?
Where do I buy these things?

RO = Reverse Osmosis

What is your area water's TDS?

I have two articles on my website which document plumbing a machine in with JG parts along with the water softener from CC:
Plumbing in an Espresso Machine - Part 1
Plumbing in an Espresso Machine - Part 2
If you eliminate the portion that goes to the espresso machine off the Tee, and replace the Tee with a 90 degree elbow you will see how the whole system goes together. it is also easy to modify later to add the espresso machine. The only part not shown is that later I added a pressure regulator downstream just before the espresso machine.

Also read The Insanely Long Water FAQ.
Using the Water FAQ's information, get the Aquarium Pharmaceuticals GH+KH kit to test for the potential for scaling. The link is to eBay where the kit is available for about $10 shipped.

Yeah where I am Los Angeles ladwp switched sources to Colorado river water with a tds at my faucet of around 600ppm. When I started the espresso thing I had a bwt bestmax premium that was an all in one softener filter rated for my (then at 300ppm) hardness for a year at my volume. But when ladwp switched sources it killed the bestmax in a few months. So I now blend RO and a new bwt bestmax in line to achieve the scaa standard. Works perfectly. I got mine from apec water. But there is a water store in Glendale that sells good ro units called aquatron. You can choose to do it a number of different ways but I found that I could not get the water Clean enough without the RO. Even on max softening setting the bwt still would not get below 150ppm given how hard the water was. I have the ladwp full water report if you want it. I emailed back and forth a lot with a guy there explaining it to me.

https://www.yelp.com/biz/aquatron-glendale
This one?
Do they install?
I wonder why they have such a bad rating of 3/5 stars.

Not to overlook the simplest solution, have you just considered buying large refillable bottles of RO water from a local water supply store (they can be very inexpensive) and then remineralizing in an empty bottle to the correct level?

For the cost/complexity of an RO system, you can purchase a LOT of bottles. You could even just set up weekly home delivery.

Some water suppliers also supply different spring water with various TDS levels...one may match ideal espresso water levels.

...and as an added bonus, if you keep 5-6 bottles around, you also have an emergency drinking water supply in case of disruption of the city supply etc. Just rotate them FIFO.

Yeah, I don't know why his rating is low for certain, but I talked to him about it and he said he has been asked by yelp to pay to get his rating up by allowing more of the positive reviews to be published and he felt like they were holding him up. I know yelp is a bit of an extortion game in that way, although i cannot say for certain that that is why his is the way it is.
Regarding the RO install, they definitely do install there, and they maintain installed systems... Which is where i would imagine they make the easy money down the line. They will price match APEC or the internet and so you can certainly get a decent deal there if you walk in and appear to know what you are talking about. I installed the RO myself and only needed some John Guest parts (which can be a bit of a pain to find locally if you are doing a self install) from aquatron. I think I paid $330 for the RO (shipped from Commerce, so came in two days). And maybe $40 in guest tubing and parts. The other thing for me about the RO is that it feeds a secondary faucet at my sink and my Fridge's water line and ice maker. So it is a great solution for all drinking water. I would guess that if you wanted any vendor to install it would be in the 600-800 range installed. But it is exceedingly simple if you are at all handy...
Just make sure you are getting a multistage system that has a remineralization cartridge after the RO...

But, as others have suggested, you can always Buy RO water in bulk. There is a store 1/4 mile from my house that sells as much as you want...

I just wanted a clean solution so i could not worry about it again...At least until the year pre-filter change interval.

Grant wrote:Not to overlook the simplest solution, have you just considered buying large refillable bottles of RO water from a local water supply store (they can be very inexpensive) and then remineralizing in an empty bottle to the correct level?

For the cost/complexity of an RO system, you can purchase a LOT of bottles. You could even just set up weekly home delivery.

Some water suppliers also supply different spring water with various TDS levels...one may match ideal espresso water levels.

...and as an added bonus, if you keep 5-6 bottles around, you also have an emergency drinking water supply in case of disruption of the city supply etc. Just rotate them FIFO.

Yes, I should look into that.
I prefer the simplicity of that approach, but I don't really know any good providers of water.
BTW, do I really have to re-mineralize?
Any suggestions for LA people?