RODI ratio too low and can't get higher

ps2cho · May 18, 2016

hey guys

I moved house and with the increased water pressure of 70psi I'm getting a 2.9x ratio

I've cut the flow restrictor all the way down! I can't cut it any further....

What else can I do here? What could be the issue why I can't get closer to the 4:1 ratio I need to not foul the membrane?

It's a Spectrapure 90gpd unit.

twilliard · May 18, 2016

@AZDesertRat
We need help here!

ps2cho · May 18, 2016

He was assisting on another forum but went quiet so maybe he's busy, but wanted to try and figure it out before I leave town in a few days as I'd like to make some good water as I'm almost out of top off water

Opus · May 18, 2016

The 90gal unit is rated at 3:1.

ps2cho · May 18, 2016

In the manual it says to aim for 4:1...

mcarroll · May 18, 2016

I think your flow restrictor is partly blocked. Try removing it completely and see if you get the expected result. (Then you know if you need a new one.)

ps2cho · May 18, 2016

Just installed a brand new flow restrictor. At stock length it was giving me 1.4x. I again slowly started cutting it down, and ended up near the end topping out at 2.7x ratio.

I'm lost here...

Best I got was:
750g / 1min waste
276g / 1min RO
= 2.7x

Im measuring using my electronic scale and tare'ing out the weight of the cup I am using, so I am sure its not my math.

mcarroll · May 18, 2016

How was it with no flow restrictor in place?

mcarroll · May 19, 2016

I guess it's also conceivable your membrane is full of holes from (e.g.) chlorine.

That's the only scenario I can imagine where more water than expected passes through the membrane. (Never heard of this actually happening, just speculating.)

ps2cho · May 19, 2016

With it removed the system drops to 30psi because there is no restriction so I didn't bother measuring as I think that's evidence enough?

Opus · May 19, 2016

ps2cho said:
In the manual it says to aim for 4:1...

I wonder if the manual is out of date. The manuals online show 2009 and 2010 as the last revisions, not sure which exact model you have. The newer RO unit manuals say 3:1 and the website says 3:1 for the 90gpd units I looked at. I would call or email spectrapure and see what they say. I did see AZDesertRat say in another post that soft water and low tds you can do 2:1 and 3:1 if moderately hard. He is the guru so I would do whatever he says. If sounds like you will be OK unless you have really hard water and high tds. I hate to say it but in the 20 years I've owned an RO unit I've never checked the ratio, I just know it takes about an hour to fill my 5gal bucket and that is what I go by.

cmcoker · May 19, 2016

Whats the TDS?

ps2cho · May 19, 2016

The whole reason I am going through this ratio is because my RO is only giving me 90%. On 500 tds my RO only water is coming out at 40 and AZDR advised me to fix the ratio first then let the system flush clean and see if the membranes performance would improve...

Well it seems I can't get the ratio right so maybe my membrane is toast.

I'm not really sure how since I don't make a lot of water and have always changed filters annually.

My membrane was running at 98.4% maybe a year ago and sometime between then and now it's tanked.

abinder · May 19, 2016

Is it the MaxCap 90 that you have? That model is advertised to have a 2:1 ratio.

ps2cho · May 19, 2016

No I have the refurbished unit.

mcarroll · May 19, 2016

Opus said:
I wonder if the manual is out of date. The manuals online show 2009 and 2010 as the last revisions, not sure which exact model you have. The newer RO unit manuals say 3:1 and the website says 3:1 for the 90gpd units I looked at. I would call or email spectrapure and see what they say. I did see AZDesertRat say in another post that soft water and low tds you can do 2:1 and 3:1 if moderately hard. He is the guru so I would do whatever he says. If sounds like you will be OK unless you have really hard water and high tds. I hate to say it but in the 20 years I've owned an RO unit I've never checked the ratio, I just know it takes about an hour to fill my 5gal bucket and that is what I go by.

+1

@ps2cho: The ratio is going to be specific to the membrane (which you change every year or few), not the ancient filter housing anyway. You should probably be targeting 1:3....which means for intents you're already there.

abinder · May 19, 2016

mcarroll said:
+1

@ps2cho: The ratio is going to be specific to the membrane (which you change every year or few), not the ancient filter housing anyway. You should probably be targeting 1:3....which means for intents you're already there.

Agreed.

AZDesertRat · May 19, 2016

In Phoenix with 500+ TDS and extremely hard water you need 4:1 or higher.
I would call Spectrapure and talk to their tech support.

Opus · May 19, 2016

In the OP you said you moved. Did you make sure to keep the RO membrane wet during the move?

ps2cho · May 19, 2016

No I just disconnected and moved it. Maybe that's what happened?

It sat for about 2 days in the yard til I plugged it in so likely would have dried out.

I'll stop by Spectrapure and tell them and get a new membrane if needed