Bad tasting Reverse Osmosis (RO) water can be the result of several issues, but roughly fall into 3 main categories. System component failure, problems with the source water, or problems with the water cleaned by the RO. This assumes the RO isn’t brand new and has been flushed thoroughly (at least a tank or 2) before drinking from it.
It’s also important to recognize that “bad tasting” is a spectrum. Does it taste foul like it’s contaminated (often with an accompanying smell) or more of a flat, metallic, stale or even bitter flavor. The first is more significant and means the RO is not performing like it should or there is a source water problem, the second requires an off-the-shelf solution.
Let’s look at the categories, starting with the most serious problem.
System Component Failure
Contaminated or Expired Filters: Any filter will have a life span and if that timeframe runs out, they can harbor bacteria, mold, accumulated contaminants or be unable to collect any more new contaminants. Depending on the brand, size of filter and filter ingredient, that life span can be anywhere from 6-12 months.
Fix: Check the maintenance schedule and replace any filters required. If this contamination got into the filter connections and tubing, you should probably also sanitize the system fully before installing new filters.
Contaminated or Expired Membrane: The RO membrane is the heart and soul of the RO. They have a life span just like the filters do, but it’s typically longer at 24-36 months. But there is another challenge with membranes in that they are dependent on the prefilters before it. If those filters have been used beyond their life span, become clogged or contaminated, that can cause the membrane to stop performing as it should.
Fix: Replace the membrane.
Source Water
This is much more common when the source water is from a well or source that isn’t treated by a municipal/rural water company. Most often it’s described as an egg or sulfur smell that isn’t so much tasted in the water as it is smelled when filling a glass or taking a drink. That usually means there is hydrogen sulfide in your source water/well. It produces a gas, and while ROs are great at removing solids and chemicals, they are not as effective with gasses that can seep through the membrane.
Fix: It would be a good idea to get your source water tested first. If you don’t have a water softener with whole home filtration set up already, that would be a recommendation as well. If you do, then contact your local well company who can offer other solutions and sanitize/repair the well if needed. You’ll also need to do a system sanitization and probably replace your filters.
Finished RO Water
This is most often described as stale or metallic. The reason for this is that water which passes through the filters and membrane is void of nearly all minerals. Minerals are what give the water taste so if they aren’t there, it can be stale. The other issues is that since there are no minerals dissolved in the water, the water more easily takes on the taste of the container it’s stored in. For RO systems, that’s the storage tank with it’s stainless steel and rubber bladder liner.
Fix: Many ROs will have a post tank carbon filter to remove this taste and while that solves the taste problem, it doesn’t solve the mineral problem. Drinking water without minerals causes long term health issues. So a better solution is to use a remineralization filter. The best location for this is before the tank to maximize the waters time with the minerals and to provide good concentrations. If that’s not possible, then post tank will also work. There are several of these available off the shelf, including ours, just be careful about the ingredients they use and where they are manufactured.
