RoDi Advice

[CStrickland]

Hi all,
I'm having a little trouble with my rodi unit. I'm not optimistic that I'll get a response from the manufacturer over the weekend (don't it always happen on a Friday night?) so I thought you all might point me in the right direction
My rodi is only making like 2 1/2 gallons an hour

I've been running a refurb spectrapure 90 gpd for 3-4 months making about 10g weekly for topoff and waterchange. When I first got it I ran each can by itself to clear any junk out. Every time I make water I take off the di can and run it for 10min (I use that water for my freshwater critters). I have twice bypassed the flow restricter to make a ghetto flush (once when I was doing a big wc a month or two ago and once today). My sediment filter got sooo gross, so I bought a zetasorb sediment filter in prep for filling my new 120. I put it on today and tried to make a lot of water. Nope.

I honestly haven't paid much attention to the thing. It made water, I smiled. Happy happy. I did notice a dip in pressure right before I changed out the sediment filter, it's back to 80psi with the new one. I have collected some numbers that seem important from reading other threads, but idk what any of it means really, so sorry for the long post and I don't have comparators from before cause I didn't mess with it when it worked good.

• My muni uses chloramine, but not a lot compared to other places.
• Temp:48f (I did verrrry carefully bring this up to 60 just to see, nothing happened but maybe it takes a long time for the inside parts to warm up)
• Tap tds: 88
• Waste tds: 110
• Production rate: 150ml per minute (900ml waste)
• My di hasn't changed color at all, and still 0tds.
• The flow restricter is in a red tube, and already cut to <1". From the web it looks like the red tube restricter is for hard water?
• When I take out the di, it seems to fill the empty can faster. Is that possible?

All help is appreciated. I have a lot of water to make and I won't be done until next month at this rate.

[outy]

Measure without DI to see if your blocking flow.


Measure output and waste lines to check and see if you have 4-1 ratio.


You can use the different capillary restrictors to tune your flow as needed.



I can tell you my cheap ebay 75gpd membrane [cheapest one they have] is doing over its rated amount, and producing 0 tds before DI and I'm running a 50gdp restrictor [green] I believe.

[bobbravo2]

Your waste to production ratio is off. 150/900 is 1:6, not 1:4. You need to use a smaller restrictor.

[slief]

Originally Posted by bobbravo2

Your waste to production ratio is off. 150/900 is 1:6, not 1:4. You need to use a smaller restrictor.

That or he has low water pressure.

I'd check the water pressure as well as what Outy suggested. If the pressure is low, your rejection ratio won't be good as good as it should be which will lead to low production. The minimum pressure should be 50 PSI and 60 to 80 PSI is ideal to get the full GPD rating out of the RODI units.

[Vinny Kreyling]

Low water pressure & cold water will absolutely ruin you production rate.
You found out when your prefilter was clogged by the pressure drop.
Red restrictors are for water over a hardness of 180, no mention of what yours is.
2.5 X 24 = 60 GPD, not that bad for cold water.
10 Gallons/ week is very little, you would be better served with a container you fill every so often because these units work better the longer they run.
I have a 55 gallon container I fill, today I'm making 45 gallons.
And as mentioned you want a 4-1 waste to production ratio.

[CStrickland]

Originally Posted by outy

Measure without DI to see if your blocking flow.
Measure output and waste lines to check and see if you have 4-1 ratio.
You can use the different capillary restrictors to tune your flow as needed.
I can tell you my cheap ebay 75gpd membrane [cheapest one they have] is doing over its rated amount, and producing 0 tds before DI and I'm running a 50gdp restrictor [green] I believe.

Without di seems like better flow
I do not have 1:4
The capillary restricter is already cut almost to the nub, that's how they sold it to me. There's no tube left to trim.
I tried taking off the di and putting back on. It's not difficult to seat, and wiping off the seals and rubber doesn't change anything

Originally Posted by bobbravo2

Your waste to production ratio is off. 150/900 is 1:6, not 1:4. You need to use a smaller restrictor.

It can't be trimmed any smaller.

Originally Posted by slief

That or he has low water pressure.
I'd check the water pressure as well as what Outy suggested. If the pressure is low, your rejection ratio won't be good as good as it should be which will lead to low production. The minimum pressure should be 50 PSI and 60 to 80 PSI is ideal to get the full GPD rating out of the RODI units.

Pressure is still 80 psi

Originally Posted by Vinny Kreyling

Low water pressure & cold water will absolutely ruin you production rate.
You found out when your prefilter was clogged by the pressure drop.
Red restrictors are for water over a hardness of 180, no mention of what yours is.
2.5 X 24 = 60 GPD, not that bad for cold water.
10 Gallons/ week is very little, you would be better served with a container you fill every so often because these units work better the longer they run.
I have a 55 gallon container I fill, today I'm making 45 gallons.
And as mentioned you want a 4-1 waste to production ratio.

Pressure is fine
Idk what my hardness is? I bought the refurb unit and it came with the red tube. I never queried why.

[CafeReef]

Maybe consider replacing the water lines on your rodi unit. They are cheap and easy to swap. Might just have sediment build up

[outy]

Originally Posted by CStrickland

The capillary restricter is already cut almost to the nub, that's how they sold it to me. There's no tube left to trim.

.

You might want a better selection.


I have 3, two capillary one 50 the other 75, and one large one for 100gpd membrane.


I use a 50gpd on my 75 now and I'm getting better output.


The trick for you will be getting closer to 4-1 and maybe even 3-1 if your TDS exiting the membrane is low enough.

[CStrickland]

Spoke to Spectrapure today, thought the convo might be helpful to others.
I guess the temp is really important, and they are shipping them with the restricters trimmed because people were leaving them long and blowing their membranes / DI. Between those two factors it's not crazy for production to slow to 9:1 in the winter, but it's easy to fix. I'm going to go with the valve suggested because my water temp varies a lot so I may need to change it a few times a year and the valve will be easier to access than the restricter is.

Thank you all for your ideas, it helped me focus the info I gave Spectrapure.

Spectrapure: The zeta zorb could be plugged up. It picks up finer particulates. It is a washable filter. You can spray it off with a spray nozzle. Be sure the pressure isn’t too high. Another culprit is water temp. We all lose a percentage of our production in the winter.

Me: I don't think the zetazorb would be plugged as it is brand new.
How would I know if the pressure is too high?
Would water temp account for the 9:1 rejection ratio that I'm seeing?

S: The pressure should be below 80.
The water temp would count for that. Normally a 90 gpd does about 3.5-3.75 gallons per hour. 2.5 sounds about right this time of year. Also you can get a 2 way ball valve and put it on your waste line in the winter to reduce the ratio to about a 4:1.

M: I'll slow the flow then.
Is it standard to ship a unit with the flow restricter trimmed all the way down? And do they generally ship with the red tube on the flow restricter?

S:Yes, That is a 3:1 flow restrictor when the water pressure is 60 and the tap temp 77f. However we have other flow restrictors that are not adjusted down that the end user can adjust on their own. The reason we switched to having preset on our flow restrictors is that most people didn’t adjust the standard ones and ruined their membranes and DI. When you get a ball valve choke off the handle a little and test afterwards to see what you get. 3:1-4:1 is optimal for longer filter life.

[SpectraPure]

Originally Posted by CStrickland

Spoke to Spectrapure today, thought the convo might be helpful to others.
I guess the temp is really important, and they are shipping them with the restricters trimmed because people were leaving them long and blowing their membranes / DI. Between those two factors it's not crazy for production to slow to 9:1 in the winter, but it's easy to fix. I'm going to go with the valve suggested because my water temp varies a lot so I may need to change it a few times a year and the valve will be easier to access than the restricter is.

Thank you all for your ideas, it helped me focus the info I gave Spectrapure.

Did the valve reducing it to 3:1 or 4:1 help out the production and raise the psi, and also are you making more water now that there are warmer temperatures?

Jeremy

[CStrickland]

yup, much better now. I'm keeping an eye on it as temps go up as well, so as to keep the 3-4:1 ratio as the water comes in warmer.
Thanks!