RODI GPD Explanation

[jbisDVM]

I’m assuming the GPD rating of my RODI unit means “gallons per day”. I have a BRS five stage unit rated at 150gpd. But my question is that the unit seems to produce water much faster than this. I have a pressure gauge on it and usually run it at a pressure of 80-90psi per the instructions. I can usually fill a 20 gallon brute trash can in about 2 hours. The water comes out as a slow trickle. I have a TDS meter on the unit and my input water is anywhere from 200-225 TDS and output is confirmed at 0. I have also noticed that in my last year of using it, the micron filter and carbon filter remain pretty white. I have still replaced them all because my resin exhausts and changes color but I found it strange the micron filter doesn’t ever seem dirty.

I guess my questions are:
1.) Should I be worried the unit produces water much faster than rated when I’m getting zero TDS?
2.) Is it strange my micron and carbon filters seem so clean after so much use? Maybe my source water is cleaner than most? I’m in Los Angeles.
3.) Finally- how often should I be changing the RO membranes that sit inside those white tubes that lay horizontal at the top of the unit?

 

[Buckeye Hydro]

I’m assuming the GPD rating of my RODI unit means “gallons per day”.

That is correct - gallons per 24-hr day.

 

[jbisDVM]

I’m assuming the GPD rating of my RODI unit means “gallons per day”.

That is correct - gallons per 24-hr day.

So is it common that these units produce water much faster? That’s ultimately my question- do I need to slow the rate of water production if I’m getting zero tds?

 

[Buckeye Hydro]

Assuming you have two Filmtec 75 gpd membranes plumbed in series, those membranes are factory spec'ed at 50 psi. You're running them at nearly double that pressure. So yes, I'd expect you to get more than the factory spec production as long as your water isn't too cold. Plug your water temperature and your pressure in to our calculator to show how much each 75 gpd membrane should produce. https://www.buckeyehydro.com/calculator/

Sounds like you only have two probes on your TDS meter - when what you need is three probes. You want to know TDS of the:
1. feedwater
2. RO water
3. DI water

Sediment filters filter out... sediment. So if your water is low in sediment of a size larger than the pore size of your sediment filter, it will stay pretty clean. If the pore sizes of your sediment filter and carbon block are correct, then you should not see the carbon block catching sediment. If it does, then something is wrong.

When membranes need to be replaced, you'll typically see at least one of the following symptoms:
1. Membrane produces water slower than it should
2. Membrane produces water @ higher TDS than it should. You'd never know this because you don't have a TDS meter probe on your RO water.

Get your replacement filters and membranes and resin from this R2R Sponsor: www.buckeyehydro.com

 

[Buckeye Hydro]

So is it common that these units produce water much faster? That’s ultimately my question- do I need to slow the rate of water production if I’m getting zero tds?

feel free to call us to discuss if our reply above doesn't make sense to you.