I'd like to first comment on how happy my husband and I are with this system now, but first I will note some errors on my journey to find the best filter.I did not know much about RO systems or much about any water filter or water specifications (what's good, bad or necessary for our health).I was also looking for an affordable but top quality way of drinking clean water so I had assumed that getting this filter would solve all my problems.I bought this countertop RO filter (without the calcium carbonate filter which is about $20 bucks cheaper), about two weeks later my husband had his first gout attack.I then started to do my research and I learned that there are studies suggesting that because the RO filter system removes EVERYTHING (good and bad minerals and impurities) out of the water and because when water is acidic it tends to compesate by taking from other sources on its path, so it will take minerals out of your body. Absolute clean will also corrode metals, it will leach minerals in contact with metals, it will do the same to our bodies. I started to panic on the inside knowing that my husband was suffering in terrible amounts of pain that wouldn't stop and to know that it was my fault, my lack of research. I contacted the seller and they helped me to get the calcium filter that I needed to stabilize the water. To see my husband in so much pain as I hand't seen before I was considering returning the filter. But I did more research and I found that we needed the calcium and other minerals in our water. The RO filter alone can potentially be a problem for some people but with proper research you'll be fine. My suggestion is to buy the APEC countertop RO filter with the CALCIUM CARBONATE FILTER. It's called Alkaline, instead of saving a few bucks. Why? Because studies suggest the importance of minerals in the water and that acidic water will leach the minerals out of your body. Our body will try to balance it out and water does the same thing. Our body needs a certain level of PH, around 7.3 PH, and acidic water will have the PH at the different level that our bodies need. I strongly suggest that if you are considering RO filter to include the filter that balances the PH in the water. Some side effects can potentially show signs long time after you've been drinking acidic water and it's not worth saving a few bucks and putting your health at risk.If you bought this filter you can buy the calcium carbonate filter and add to this. Simply contact APEC CS if unsure which one, they were super fantastic and helpful.It's been almost a month and we only installed the calcium filter yesterday (feb/ 05/18), my husband is still recorvering from the gout but we believe that this will help him a lot and hopefully never suffer from gout again.Another thing worth mentioning is that this filter will waste a lot of water but as a conscious green person I cannot bear the idea of adding more waste and not reclycling or reusing what we already have. So, be creative. My creative way of not letting the waste water go to waste is that I fill jars and I reause for dishes or for plants. If you use for plants it's better to let the water sit for at least a couple of days before watering the plants.To me, it makes sense to repurpose something that otherwise would go to waste. If you don't like the idea of doing your dishes with "waste" tap water then you can water your garden or find some other ways of reausing it.The TDS result will change when you add the calcium filter but THAT'S OKAY, it's only the good stuff.TDS RESULTS:TAP = avg of 44RO (without calcium filter) = 3RO with Calcium filter = 15But it also changed the PH level. Please see the images and also note that this isn't the best PH tester because it's one that we bought for the aquarium but we decided to use what we had to notice the difference. We will buy a specific PH tester for drinking water in the filter and maybe I will add it to the review. Because I only had the idea to take a photo minutes later it's not showing result exactly as I first saw it but it will give you an idea.The PH comparison image:Notice that that the yellow square highlights the ph. Notice that with the calcium filter that the color is more neutral and to the desired level that we need?Below the old filter, constitutes this RO filter without a calcium filter. The color looks more pale and acidic.Inside the pink squares it analylizes the alkalinity of the water.Again, the colors aren't as vibrant because the strips were drying when I had the idea of taking a photo. But in the future I will possibly add it here the results of my future tests for the specific PH tests.Bottom line is: We are VERY happy to finally undestand more what is that we need and how to achieve clean and healthy water. Do your proper research to learn for yourself more. It's not worth saving a few bucks to get the filter without the calcium filter. It's better to think long term.Also, this filter generates water to be wasted can you find ways to reuse and recycle the water?The customer service was extremely helpful and I can't thank them enough for helping me out. Specially because I was freaking out on the inside to see my husband in such terrible pain. We suspected that it was this issue w/ the water because gout can be formed by many things such as eating meat, which we don't do, we also discarded some other things, which lead us to believe that it was the difference in the water. But, we can solve everything and what I learned from this is the importance of doing extra research to make sure it's a good, healthy decision.I almost forgot to mention that when you use the filter, the filtered water will pour slower than your tap. Here our tactic plan is to fill up 1 gallon of glass jars while we are in the kitchen taking care of things. I timed and for me it takes me about 18 minutes to fill up one gallon. It's not a problem at all for us because while in kitchen cleaning or cooking I am also filling up the daily jugs of water. We strive to drink 1 gallon of water each.Now that we figured it out I'd say that this system with the calcium filter is a 10 out of 10. Buy with confidence but do your research beforehand.