Kitchen RO unit?

[Pythonfriend]

i know about it from aquaristics.


True reverse osmosis (thats what RO stands for, RO is quite a meaningless 2-letter abbreviation, damn i hate those), anyway, true reverse osmosis requires pressure. If your water supply comes with enough pressure, you can hook up a reverse osmosis device to that, otherwise you need a pump that delivers high pressure at very low flow rate.

Typically they have 3 stages: stage 1 is just a very fine filter to keep particles out, stage 2 is an active charcoal filter that will remove most chemicals, stage 3 contains the osmosis membrane which holds back salts, ions, and any large molecules. On the pressurized side of stage 3, the bad stuff concentrates, so we have two designs: One has a valve or some kind of system that allows you to withdraw wastewater from stage 3 during operation, the other would be that you need to open and wash stage 3 regularly. Sometimes the filters need changing.


A gravity filter cannot run with a membrane necessary for true reverse osmosis, without enough pressure these membranes are virtually waterproof. If you put salt water on one side and purified water on the other, they will do osmosis instead of reverse osmosis and pump the pure water into the salt water. It takes pressure to force them into reverse mode. So, gravity filters cannot remove ions or salts, but gravity filter systems can remove particles, reactive chemicals, fat-soluble chemicals, and if they are bioactive also fertilizer remnants.


For reptiles or other pets, a normal filter or gravity filter should typically be enough.

Reverse osmosis is typically overkill, except for valuable and sensitive fish, if your fish will only breed at a water hardness that is one order of magnitude lower than what you can otherwise get you have no other choice. Even in aquaristics its quite high-end, up there with coral reef aquariums. You need it if your water really has a problem with too much salt or any toxic ions, like copper or uranium or mercury, or serious chemical pollution. Normal filters can remove lots of chemicals on their own, just a few chemicals as well as salt go through.

Unless you have a known issue with your water, or too much salt in your water, regular filters should do the job just fine. But then, you can get a 3-stage reverse osmosis device to hook up to your pressurized cold water supply that produces a few gallons per day for maybe 200 dollars, if you look for high-end aquaristics supply.


Then, one issue with osmosis water i need to mention: If done properly, it is so low in ions that its PH-value becomes unstable. Water hardness stabilizes the ph-value (acidity) of the water. Basically just by being unusually pure, it tastes like crap, it tastes weird. So you need to add a bit of the right product, carbonates and other ions and minerals, then its perfect. again, available in high-end aquaristics supply, in aquaristics when people use osmosis water that is too pure, the instability in acidity can have disastrous effects. With regular filters you dont have that problem because ions go through.


example image of a nice small unit from a german company: