RO/DI Diagnosis

fatdaddy · 07/18/2009, 06:25 PM

I'm trying to figure out what's wrong with my RO/DI unit. I noticed that the pump was running non-stop. It seems that it's not building pressure on the RO side, so the pump isn't turning off.

Also, my RO output is 80 ppm and all my DI exhausted before it should have. I think my RO output is usually more like 12.

I replaced the membrane, but the problem seems worse then it was before. I'm stumped.

I'm thinking that I must not have gotten a good seal when I installed the membrane. Does that seem reasonable?

Any other thoughts? I'm going on a two week trip monday, so I'd like to nail the problem.

fatdaddy · 07/18/2009, 07:07 PM

Update: I lightly applied some silicon grease to the membrane o-rings and reinstalled. It's now running at 4 ppm.

However, it still doesn't build enough back pressure on the filtered side to turn off the pump. Still puzzled.

1DeR9_3Hy · 07/18/2009, 07:10 PM

When you say pump, do you mean a high pressure pump designed for your ro unit or do you mean your pump that pressurizes your houses plumbing?

Also, do a quick test of the tap water (measure the TDS) then measure the RO output. The tap water is the denominator, the RO is the numerator. Divide them.

This will give you the RO membrances rejection rate, i beleive a good one should be above 90% or 95% rejection.

fatdaddy · 07/18/2009, 07:28 PM

Quote:

Originally posted by 1DeR9_3Hy
When you say pump, do you mean a high pressure pump designed for your ro unit or do you mean your pump that pressurizes your houses plumbing?

I use a booster pump because my household pressure is about 35psi.

Quote:

Also, do a quick test of the tap water (measure the TDS) then measure the RO output. The tap water is the denominator, the RO is the numerator. Divide them.

This will give you the RO membrances rejection rate, i beleive a good one should be above 90% or 95% rejection.

Tap water is at 401 tds and my current RO output is at 4ppm, so I'm getting about 99% rejection rate. It's a new membrane, so that sounds about right.

Mike31154 · 07/18/2009, 11:36 PM

Does your booster pump have an adjustment on it to regulate pressure? Maybe it was inadvertently set too high & that's why it's not cutting out? Do you have a pressure guage installed somewhere on the RO unit to monitor pressure?

1DeR9_3Hy · 07/19/2009, 06:34 AM

Im sorry i cant offer any advice, i run mine at 35 psi off my main pump. I know it does not put out its rated GPD, but its putting out 0 tds so im happy.

Buckeye Hydro · 07/19/2009, 07:51 AM

IN your type of set up, the booster pump is typically kicked off by a pressure switch installed on the DI "out" tube.

Check to see if the valve on the DI "out" tube is working - you must have somehing like a float valve or other shut off at the end of that tube - if it is leaking the pressure won't build up and the pressure switch won't kick the pump off.

Russ

fatdaddy · 07/19/2009, 11:57 AM

I think I figured it out. I had a clogged pre-filter (1 of 3), so it reduced the pressure to the point where the RO couldn't function when there was any back pressure and couldn't build more then a modest amount of pressure. More testing, but I think I nailed it.

Buckeye Hydro · 07/19/2009, 12:10 PM

That would do it. Must have been really clogged. A pressure gauge works wonders to troubleshoot clogged prefilters...

Russ

fatdaddy · 07/19/2009, 12:26 PM

Quote:

Originally posted by BuckeyeFS
That would do it. Must have been really clogged. A pressure gauge works wonders to troubleshoot clogged prefilters...

Russ

I'll add one at the head of the RO.

07/18/2009, 06:25 PM	#1
fatdaddy Registered Member Join Date: Apr 2007 Location: Northeast Florida Posts: 1,191	RO/DI Diagnosis I'm trying to figure out what's wrong with my RO/DI unit. I noticed that the pump was running non-stop. It seems that it's not building pressure on the RO side, so the pump isn't turning off. Also, my RO output is 80 ppm and all my DI exhausted before it should have. I think my RO output is usually more like 12. I replaced the membrane, but the problem seems worse then it was before. I'm stumped. I'm thinking that I must not have gotten a good seal when I installed the membrane. Does that seem reasonable? Any other thoughts? I'm going on a two week trip monday, so I'd like to nail the problem. __________________ "We are what we repeatedly do. Excellence, then, is not an act, but a habit." -- Aristotle

07/18/2009, 07:07 PM	#2
fatdaddy Registered Member Join Date: Apr 2007 Location: Northeast Florida Posts: 1,191	Update: I lightly applied some silicon grease to the membrane o-rings and reinstalled. It's now running at 4 ppm. However, it still doesn't build enough back pressure on the filtered side to turn off the pump. Still puzzled. __________________ "We are what we repeatedly do. Excellence, then, is not an act, but a habit." -- Aristotle

07/18/2009, 07:10 PM	#3
1DeR9_3Hy Registered Member Join Date: Dec 2007 Posts: 2,575	When you say pump, do you mean a high pressure pump designed for your ro unit or do you mean your pump that pressurizes your houses plumbing? Also, do a quick test of the tap water (measure the TDS) then measure the RO output. The tap water is the denominator, the RO is the numerator. Divide them. This will give you the RO membrances rejection rate, i beleive a good one should be above 90% or 95% rejection. __________________ I hope it never catches on, I like having the oldest tank on here and I don't have to worry about calcification, bio pellets, Vodka dosing, DSBs, Chaetomorpha (I don't even know what that is) Carbonite hardness and all of these other things many people worry about. If I had to think about all of that stuff I would get a stroke. My test kit came in a wooden box and the directions say to keep in a cool chariott. I throw some food in the tank, wave hello to the fish and go out with my wife and have a nice glass of merlot with dinner. Have a great day but most of all, have fun. -PaulB Current Tank Info: 27 Gallon DAS softy/fish reef

07/18/2009, 11:36 PM	#5
Mike31154 Registered Member Join Date: Apr 2008 Location: B.C. Canada Posts: 1,555	Does your booster pump have an adjustment on it to regulate pressure? Maybe it was inadvertently set too high & that's why it's not cutting out? Do you have a pressure guage installed somewhere on the RO unit to monitor pressure? __________________ Mike Current Tank Info: 77g sumpless sw with rock, sand, a few critters, fishes & polyps. Lights, pumps.....

07/19/2009, 06:34 AM	#6
1DeR9_3Hy Registered Member Join Date: Dec 2007 Posts: 2,575	Im sorry i cant offer any advice, i run mine at 35 psi off my main pump. I know it does not put out its rated GPD, but its putting out 0 tds so im happy. __________________ I hope it never catches on, I like having the oldest tank on here and I don't have to worry about calcification, bio pellets, Vodka dosing, DSBs, Chaetomorpha (I don't even know what that is) Carbonite hardness and all of these other things many people worry about. If I had to think about all of that stuff I would get a stroke. My test kit came in a wooden box and the directions say to keep in a cool chariott. I throw some food in the tank, wave hello to the fish and go out with my wife and have a nice glass of merlot with dinner. Have a great day but most of all, have fun. -PaulB Current Tank Info: 27 Gallon DAS softy/fish reef

07/19/2009, 07:51 AM	#7
Buckeye Hydro .Registered Member Join Date: Sep 2006 Location: Cincinnati, Ohio Posts: 4,857	IN your type of set up, the booster pump is typically kicked off by a pressure switch installed on the DI "out" tube. Check to see if the valve on the DI "out" tube is working - you must have somehing like a float valve or other shut off at the end of that tube - if it is leaking the pressure won't build up and the pressure switch won't kick the pump off. Russ

07/19/2009, 11:57 AM	#8
fatdaddy Registered Member Join Date: Apr 2007 Location: Northeast Florida Posts: 1,191	I think I figured it out. I had a clogged pre-filter (1 of 3), so it reduced the pressure to the point where the RO couldn't function when there was any back pressure and couldn't build more then a modest amount of pressure. More testing, but I think I nailed it. __________________ "We are what we repeatedly do. Excellence, then, is not an act, but a habit." -- Aristotle

07/19/2009, 12:10 PM	#9
Buckeye Hydro .Registered Member Join Date: Sep 2006 Location: Cincinnati, Ohio Posts: 4,857	That would do it. Must have been really clogged. A pressure gauge works wonders to troubleshoot clogged prefilters... Russ