RO Membrane replacement frequency and water

[travis32]

So, I have a RODI unit from BRS it's the 150 gph 2 membrane RO unit. I used it heavily for 2 years for my 220 system, then I had to sell the system since we were selling the house. I kept most of the equipment just not the aquarium.

I hooked it up to my new house and started using it for drinking water. I changed out the carbon sediment filters a couple times in the last 2 years in the new house. (3 stage filters) plus two RO membranes).

In total the entire RO unit is around 4 years old. It goes to a 5 gallon holding tank and to the DI resin chamber (after the drinking water).

I should also mention the RODI unit ALWAYS had a softener on the cold water input to the RO unit.

The TDS from the RO unit is showing as 5. The TDS after the DI is showing 0.

So, two questions after all that... 1.) When do I replace both RO membranes? Do I wait until TDS creeps up or just do it at the 5 year point?

2.) I've read many sources say that 0 TDS water is dangerous to drink for humans. We're at some not replacing the trace elements and minerals. And something to do with the water being chemically imbalanced. So, is 5 TDS water safe to drink? I didn't think I'd ever have the issue of too clean water...

 

[mcgyvr]

1) Typically you replace the membrane when the rejection ratio falls outside of its specified range.. (some are 99%.. some 97-98%.. some 93%,etc...) so you need to know TDS before RO and TDS after and calculate..

2) Drinking RO water (typically not zero TDS) is not dangerous at all and neither is drinking water post DI stage (zero TDS water) unless you suffer from malnutrition or have other serious..serious.. health problems already .. A "normal/healthy" human should have no problem with it in normal amounts.
Many people do not like the "taste" (or lack of taste really) from zero TDS water. Its why most bottled water puts minerals back into it for "taste"..

 

[bertoni]

I agree that RO and RO/DI both are safe to drink as long as there's no bacterial contamination. I stopped drinking RO/DI due to concerns about bacterial load, but I never had a problem.

What is the input TDS? I agree that the rejection ratio is a key issue.

 

[mann1139]

If you don't like the taste out of the RO, you can buy inline 'taste filters' that seem to help. They are similar to what is in a fridge with a water dispenser.

If all you are using the filter for is drinking, I would remove the DI resin. It's expensive, and it isn't necessary for drinking water.

I tee off my drinking water before the resin for the same reason.