At some point in your brewing career you are going to become interested in taking your water chemistry to the next level. As part of that, you might come to the realization that you want to improve the quality of your water and stop using the water from a garden hose or you might want to cut down on the inconvenience of having to go to the store to get your water. I had waited a long time to do it, but I've had my system installed for 2 years now and I don't regret the expense one bit.
I put together a guide on reverse osmosis systems detailing
- The basic components of a RO (Reverse Osmosis) system
- Some of the considerations when choosing a system
- A brief explanation of how they work
- How I chose to install my system
Here is a link to the full guide:
A very nice article. Below is one of the statements from the article. It is important to note that the reduction in EC/TDS is mainly done by the RO membrane. The sediment and carbon filters do not play as much of a role compared to the membrane. An RO membrane will last for a very long time but the sediment and carbon filters should be exchanged every 6 months.
When I first bought the system, I was accepting that I would be replacing filter sets every year. After seeing the measured performance of the system, I would say that after 2 years, there does not seem to be a noticeable difference in output, so I would consider the filters still operating properly.
The sediment filter will remove the particulate that can clog the membrane. The carbon (GAC) filter removes odor and chlorine. If you are on city water then you will have chlorine present. With commercial RO systems the carbon is used to remove the chlorine so that it does not damage the RO membrane. The membranes have gotten better but I still see a lot of companies monitoring the water supply to ensure no chlorine goes to the RO membrane.
It would be difficult to monitor on a residential system so it would be best practice to replace at 6 months. Unless then carbon filter is a unique size I would not spend extra money on name brands. The canisters used in residential systems tend to be a standard size.
It is not unusual to see TDS creep up on storage. I have seen on mixed bed DI systems for 18 megohm water. Once the water is flowing the resistivity will increase from 10 to 18 megaohms. I would think it is from carbon dioxide forming carbonic acid that would disassociate into hydrogen and bicarbonate ions. Not sure how the atmospheric CO2 gets in the water in a sealed system. Either way as you use the system there will be a little change.
Side note for people with an RO system and no EC/TDS meter. Definitely worth the money for an inexpensive tester. If a membrane gets a tear then the output will be the same as the input and the membrane has to be replaced. It is one of those things that you will not know unless you measure another parameter (hardness, chlorine, iron, etc) as an indicator the membrane is no longer functioning.