Attempting to fix RO DI excessive consumption

[lyscer]

So I bought a 6 stage BRS RODI unit a few months back and have noticed that I burn through DI resin like crazy. I have my RO unit plumbed directly to a float valve in my DT. After much reading on the forum here I decided that my problem was due to this.

TDS after membrane and into 1st DI stage = 70ish when the unit has only been running a short time

TDS out of first and into 2nd is 0. Out of 2nd is 0 too.

I found when I did large batches of water the TDS going into the first chamber was much lower like 20s. So I decided to hook up a reservoir to feed my tank but that I could just turn on every weekend to fill up (flooded too many things due to forgetting so auto shutoff was a requirement). Here are some pictures of what I came up with.


The lines going in are deceiving. They are really about 5 feet above the tank. They gravity feed another float valve that is in the sump.

 

[pugcrush]

70 is really high going into your DI. It should be 3 or 4. What is your pressure going into your unit? Also, TDS for your tap water?

 

[ermartin]

almost seems like your meter is hooked up to your waste water

 

[alxjrz]

It sounds like your membrane is the problem. make sure your membrane is well seating in the membrane housing and your connections of rejected waste water and proper restrictor calibrated. only reason you should be getting readings of 70 out of a new (months old) membrane(depending were you live can contribute). I am guessing your membrane is improperly sealed in the housing. If not your membrane has been damaged by running tap water without proper carbon filtering, not filtering proper "chloramine" if your water municipality uses it at some point in disinfecting will burn threw your membrane. Hope this help as guidelines to troubleshoot your problem.

 

[Jimbo662]

What's the pressure going in? I was burning through resin too and finally added a booster pump. My pressure went from 45 to 82 and I'm getting better results.

 

[TheEngineer]

You should be getting in the mid to high 90% rejection from the RO membrane. The water going into your DI has very high TDS. What is your source TDS? I agree with others that something is off with your RO membrane.

 

[AZDesertRat]

What is your water pressure, water temperature, tap TDS, water calcium carbonate hardness, (are you using softened water or not?), RO only TDS after its been running awhile and your exact measured waste ratio?
The first thing you need to do after answering the above is to install a DI bypass valve so you can flush the initial TDS creep out before it hits the DI resin.

What DI resin are you using, is it fresh and sealed in vacuum sealed mylar foil bags and kept in the refrigerator or is it bulk resin out of a bag that has been previously opened and possibly old?

What are you measuring the TDS with and how are you doing the test? Do you draw a sample in a squeaky clean clear glass drinking water glass washed by hand in very hot water so no water spots or dishwasher anti spotting agents to skew the results? Is the meter an ATC model and is it calibrated and kept clean between each reading and capped when not in use?

 

[bmeudy]

Make sure the membrane is not in backwards!

 

[lyscer]

Thanks for all of the help!


Water Pressure: 55 psi
TAP TDS: 189
Water Temperature: 57.6 F (Taken from the waste water on the RO unit so I could get the water temp that the membrane is seeing)
Water Softner: No
Water Calcium Carbonate Hardness: I don't have a way to test this
TDS RO Only: 43 (Do you have a particular procedure for calculating how much waste to production water I should do?)
DI Resin: BRS Deionization Resin - Color Changing single canister vacuum sealed packs. I keep it in my garage which at the moment is like 40ish degrees so pretty much like a refrigerator
TDS Meter used to test tap water is one that came with my AirWaterIce RO unit that I bought a little bit ago and ended up selling because I wanted an RO unit with more bells and whistles. I ended up getting this unit: http://www.bulkreefsupply.com/brs-6-stage-universal-plus-ro-di-system-75gpd.html which has the inline TDS meter which is how I am testing the TDS after the membrane, 1st DI and 2nd DI chambers.

RO Unit was purchased on 9/5/2015 and I am on my 3rd replacement of DI resin. It seems to be lasting about a month before it fully changes color and TDS goes above 0.

 

[TheEngineer]

Are you on well water or city?

 

[Skynyrd Fish]

Call BRS they'll trouble shoot it with you. That sounds like a great RO unit.

 

[lyscer]

City Water

 

[AZDesertRat]

To test the waste ratio use a measuring cup that holds maybe 2 to 4 cups of liquid, should have one in most kitchens. First measure the waste flow for exactly one minute using a clock or watch the do the same for the treated water.
Your waste ratio should be somewhere between 3:1 to 4:1 waste to good. If it's much less your membrane may be plugged with solids buildup. At this point it sounds like you have a bad membrane, for whatever reason but it happens some are bad from the start. This is one reason I prefer hand tested membranes so I know what I am getting.
How are you testing the tap TDS? While I do own two dual inlines I am not a fan of them and much prefer a good handheld which is more versatile and can be used anywhere where the inlines cannot.

 

[lyscer]

I just ran the test and what I did was let the RO line run for 3 minutes to completely depressurize. I then placed the waste line in a bucket and set the RO line in a bucket right next to it and timed for 2 minutes. I then pulled the lines out, dumped them into a measuring cup and measured the following:

RO: 1 1/2 Cups
Waste: 4 Cups

So it appears as though my ratio is pretty inline. I am testing the tap TDS using the methods that you described above with cleaning out a glass by hand, then drying it, then filling it up with tap water and sticking the handheld TDS meter into it. I am fairly certain this is the TDS meter that I am using: http://theh2oguru.com/tds-ph-meters/tds-mini-handheld-meter-from-senno.html

 

[AZDesertRat]

I think you membrane may be ruptured or torn in some way. Usually one minutes flow is measured in a couple ounces or milliliters not cups.
When you say "depressurize" what exactly do you mean? Is it only the float valve on the end or do you have something else? When you add head to the discharge the waste ratio changes.

 

[lyscer]

I just let it run wide open into a drain for a couple of minutes. I have my 1/4" ball valves shut off until I am actually processing larger batches of water so that I can try to preserve some of the life on this DI resin. Anything else I can try or do I just replace the membrane?

 

[AZDesertRat]

Given your 57 degree water temp and 55 psi incoming pressure you should expect to see 57 GPD out of a 75 GPD Dow Filmtec RO membrane. At the normal 4:1 waste ratio that means you should expect to see 5 ounces per minute treated water and 20 ounces per minute waste. The 1.5 cups and 4 cups you are seeing is over 4 times what it should be telling me wate ris bypassing your RO membrane for some reason.
It could be the RO membrane is not properly seated inside the housing, you could have a rolled O ring or gasket on the membrane, a housing with a hairline crack, a RO membrane that has been subjected to water temperature over 113 degrees which melts the TFC fabric and damages the glues they are held together with, the unit has been run without sufficient waste flow for a length of time to foul or plug it or any number of other things. It may have been a bad winding from the factory? Only yu would know if any of these situations were true or not but it is not working as it should.
You can try removing the membrane from the housing, inspecting it visibly and reinserting it in the housing making sure it is all the way down but I really don't think this is the case. Other than that a new membrane is in your future.

 

[TheEngineer]

Here's a reach, but do you have the proper flow restrictor on the waste line?

 

[AZDesertRat]

The flow restrictor is a little off at only 2.6:1 but that doesn't account for the poor rejection rate and high flows.

 

[lyscer]

It has the default flow restrictor that came with the unit (550ml) which looking at their site says it is recommended for the 75GPD units. I opened up the membrane housing pulled the membrane out and looked it over and then put it back in to reseat it and I am still getting high outputs. My guess is that I was sent a bad membrane because it has always had high output like this. I just thought it was normal. So it looks like I will be buying a new membrane