RO/DI Questions

[JordanHurst]

So I just bought a 75 GPD 5 Stage RO/DI "PLUS" system from bulk reef suppy. Just wondering.. there is a 4:1 ratio of waste water to RO/DI water.
Now can you throttle down the waste line discharge to force more water through the system and less coming through the waste line?

Im just not sure how the waste water is determined? I looks like out of the RO chamber there is one line coming out goes to waste and another going to the next step (DI resin) So is there an issue pinching back this flow while monitoring the outlet TDS and insure pressure isn't to high forcing water through the whole system?
Just seems to me to make 5gal pail of water I'm pouring 20 gallons of water down the drain? Hmmm

Thanks for any information. Ill be doing some reading.
Cheers

 

[davesolo29]

not sure it will work the way you are suggesting or im quite certain they would have manufactured them that way.

i purchased a second R/O membrane and chamber so that my waste water goes thru twice.
its the uprgade kit BRS sells.

 

[AdInfinitum]

Your system will already have a flow restrictor matched to the membrane.  As long as you don't turn your in-feed down so far that it cannot supply excess volume, the system pressure will already be at the max your tap can provide.  The only way to increase the feed side pressure to improve membrane efficiency, would be to minimize in-feed tubing length and thus pressure drop or to add a booster pump to increase in-feed pressure to your membranes max rating.  Adding the second membrane to the waste line as Dave suggested is probably the easiest way to minimize waste losses although the second membrane will run at a lower efficiency since it will be running at an even lower pressure than membrane number one.

Even @ 4/1 waste it's much cheaper than buying and if it is the eco side of things that bothers you...the filtered/carbon-passed "waste" water is still cleaner than tap water for your freshwater tanks (obviously still chlorinated) or for watering your plants...

I would like to add my own RO/DI question to the thread....

Since RO water is usually high PH in the line until it has been oxygenated (due to the change in the carbonic acid/CO2 equilibrium) has anyone experimented with running their system through a chamber with calcium carbonate (calcium reactor) media in it? Much like running the acidic RO over marble chips to make "remineralized" drinking water.  It might be a good way to stabilize the ph when you need to use freshly produced RO and get a cheap head start on the calcium and carbonate levels....

 

[Blob-79]

4:1 is pretty high.

Could you tell us your pressure, tds of the water coming out of the membrane?

 

[AdInfinitum]

I think spec. on most household membranes work out to about a 3.8/1 ratio and are rated @ 50-60 psi with nominal being around 35-40 psi.  Depending on your city, house's plumbing etc. you could easily be 90 psi plus or around the nominal... We have run household units on branch lines of pressure systems at work at close to 125 psig  long term since I believe they max at 150-160 psi so your household pressures will have a large effect on the efficiency of the unit. 

 

[unibob]

I just got same unit as jordan, also finding high waste ratio. Water pressure here is 45(could be low as I did a no permanent connect at bottom of water heater on cold feed. Tds in once things turn on around 30, dropping down to 1 being the lowest I've seen. And 0 out.


Anyone use pressure tanks on the system similar to what you would use on drinking system?

 

[Blob-79]

yea 45psi is definitly going to hurt your efficiency a bit. your Tds out is great though.

ive never used a pressure tank on one of these systems myself, I have one if you want to try it out.

Myself I would recomend a water vat using float sensors and solenoid valve.

 

[JordanHurst]

4:1 is pretty high.

Could you tell us your pressure, tds of the water coming out of the membrane?

Pressure runs just around 70 lbs
It came with a dual TDS meter, 1 on the inlet to the DI resin and 1 on the outlet.
The inlet to the DI chamber afar exiting the 4 stages is at 115ppm rate now after a 5 min flush and letting the system run for 10 mins (as instructions says). On the Outlet of the DI chamber it is reading zero ppm going into water container.

Thanks for all the information guys!!
Cheers

 

[Blob-79]

would help to know the tds of the water coming out of the ro membrane, before the di

 

[davesolo29]

from what i just read he says 115 after the membrane.  if this is the case, thats way too high.  you will exhaust your DI resin real quick. 
you may want to make sure you have it hooked up correctly.

 

[Blob-79]

oh crap yea...i read it as if the 115 was after the 3 prefilters but before the membrane.  Somethings definitly not right.

 

[JordanHurst]

Yea Hmm.
-I have the red line hooked up to the tap, which leads into stage one, the sediment filter, next into the 5 micronCTO/ 2 carbon block, next into to 0.6micron+1 carbon block, next up through the RO membrane, then over to the DI Chamber. The flush line and bypass come off the back of the RO membrane and black line goes to drain and the blue line leads to the DI chamber.
The TDS reads 115ppm at the inlet of the DI Chamber and 0ppm on the outlet of the DI chamber....

TDS shouldn't be that high before the DI chamber is my thought? It was just plug and run all hooked up, using cold water, ran it for 1hr before creating any water..
Any ideas? I think the water pressure around 70psi was to high and forcing through the system to quick. I just throttled it back to 50lbs and I will monitor the TDS into the DI over the new hours

What should my inlet TDS before the DI resin should be?

 

[teebone110]

What should my inlet TDS before the DI resin should be?

If you are running a new RO membrane, it should be below 5, and possibly 0.

 

[davesolo29]

the highest mine ever got was 42 ppm before DI.  thats when i changed filter media.

 

[davesolo29]

did you say it was plug and play???  i had to remove packaging from my membrane and one of the sediment filters before use from my brs unit.

 

[JordanHurst]

everything was hooked up filters installed lines in proper order. all I had to do was un wrap mount on wall connect the DI chamber to the outlet of the system and thats it. I just ran it again for an hour with 50lb pressure. TDS 121 before DI. after DI 0ppm?

maybe they installed filters wrong or something stupid. Ill call them tomorrow or monday?

another thing was the sediment filter wasn't tightened filly and leaked a little before i tightened it as well as the DI chamber. It is only about Half full with water running. It says air can get caught but won't affect the system I need to bleed it out tomorrow

I havve Nooo idea now.. really pissing me offf haha


UPDATE: just unscrewed each canister they were ok just the first sediment filter was bent at the top and I think leaking into the next stage not being forced though. I switched the lines on the TDS meter insure they both work.. so its not that. I just flushed and will let it run for an hour. TDS before DI resin is at 114 and going down slowly.. keep posted to see what I get down to

WOOT WOOT, after an hour... 119 ppm leaving the 4 stages..

 

[unibob]

Do you know what Tds is out of the tap?  Seems something isn't working right as I have same unit and get only a high rating when I first turn on, and it will drop to 1 Tds before DI stage.

I do have a question for those members who use the system for drinking water as well. What I'm wondering is do I need a check valve on line going to DI stage? Also should I be having a shut off valve on this same line for when I'm getting drinking water that the DI stage isn't under pressure as I have a shut off on only the DI output right now.

 

[Duke]

You Don't want to drink di water, you'll want to splice a line and valve in after the ro and before the di resin

 

[unibob]

Yea that is what I have now a T before DI. Can the DI stage be under that pressure when I am getting drinking water as there is still water flowing to the DI as the valve is on/off is on output.

Heres what I have. Wondering if I need a shut off valve before di just after the T to stop pressure from going into DI section.

 

[JordanHurst]

I tested the water coming out of the tap it was 119 ppm? therefor my 4 stages are doing nothing. I followed the tubing out again... tap water is Red in, 1st sediment, then carbon blocks, out of the third one around and up to the RO membrane then blue line comes out leading to the DI and the black waste line and flush valve lead off the RO as well...

I have no idea. Im taking the whole thing apart tonight.. somewhere the flow is leaking by