Is RO rejection based on incoming TDS?

[piranhaman00]

Hi,

Is the amount of water rejected from an RO membrane based on incoming quality?

for instance, if my ROsystem rejects 95%, my 220 incoming tds water is reduced to 8 ish tds and I reject x amount of water to waste. If I were to run water that I captured through my dehumidifier which is 7 tds would the same amount of water , x , be rejected? Or because the water is much cleaner to start is there less rejected?

Debating saving dehumidifier water and running it through rodi, but if I reject half of it it’s not worth it.

thanks!

 

[Dietmar]

I think you have this thinking wrong.
As far as I know, for every 4 gal water in, then you make 3 gal for yourself and one goes to the waste.
The 95% you speak of is efficiency. So if your incoming water has 100 TDS. then the outflow of good water will have 5% TDS.
If you use your dehumidifier water, 95% of 7 TDS will be virtually 0 TDS coming out.
However you will have to buy a pump that will push that water at least 60psi through the filters of your RO system. plus you have to collect and set up a new system.
I think that if you added another filter to your system it would be less hassle all around.
This would be a DI resin filter. That would bring your water to 0 TDI. It would be the last filter in the system.

 

[Water Dog]

Rejection ratio to maintain proper flushing of the RO membrane under pressure is 4 to1, meaning 4 parts waste water to 1 part product water. You can go 3 to 1, but any higher and you will shorten the life of the RO membrane.

 

[piranhaman00]

Ok thanks!

 

[jelazar]

The water you pull out of your house's air can be nasty. It's common for the condensate in home AC systems and dehumidifers to grow algae from all the junk in the air.