Rodi Exhausting RO Membrane FAST

[ChrisKey]

I have a 75gpd rodi unit with a 10 micron sediment filter, 10 micron carbon filter, 5 micron carbon filter, 75 gpd filmtec membrane, dual (separate) DI Resin filters. So I am running 6 stages. I replaced my prefilters and RO membrane 2 months ago and just changed the DI resin 1 month ago. All was reading 0TDS. Test TDS with HM dual inline meter. I have a 550 flow restrictor from BRS.

I tested my output TDS this weekend and it was 90ppm, so something in the system isn't right to exhaust so quick. I changed DI resins and the output was 1ppm for 2 days and has now gone up to 60ppm.

Here are the tests.
House water pressure is 65psi, water is about 70 degrees.
TDS of water after sediment and carbon filters 105ppm
TDS after RO Membrane 57ppm
TDs after separate cation and anion beds 60ppm

Am I just getting bad RO Membranes or is there something else I should check? I plan to get a new set of 1 micron and .5 micron prefilters and carbon block and get a tested Spectrapure 60gpd RO Membrane, but I want to check all options before I fork out the $80 for new filters.

 

[tektite]

Your membrane is completely shot. That membrane should have 98% rejection rate, meaning that with TDS going in of 105, TDS coming out should be 2.

 

[ChrisKey]

Yep, this is the 3rd membrane I have used up in 9 months.

Our local water does not have Chloramine and I am reading 105 TDS which should be pretty good and the membrane should not exhaust so quick.

 

[tektite]

Perhaps something is wrong with the membrane housing causing the membrane to not be seated correctly or causing leaks?

 

[cdness]

Yes there is an issue with the RO Membrane it seems... There are a few things to check

1. Is the membrane installed correctly according to manufacturer specs?

2. Did you fully remove the housing to clean it before replacing the membrane? If yes, did you hook up the tubes the correct way?

3. Are you 100% sure the flow restrictor is working as designed? Verify your waste to production ration by filling two graduated cylinders or containers for 30 seconds or a minute. It should be a 4:1 wasteroduct ratio if it is working to specification.

More than likely your membrane is shot, but see if you can run through the above questions and hopefully help dig deeper into the issue.

My incoming TDS is around 450 - 650 so you have good water. It should not be that bad on the membrane or filters.

 

[ChrisKey]

1. The membrane was seated and I believe it was correct. Should be pretty straight forward here to push it down to seat it.

2. The housing was actually a brand new replacement so it should have been clean. I have the incoming on one side, then the waste is the top innermost outlet that goes to the destructor and out to the waste. The blue line is the bottom outermost outlet and goes to the **** off valve which goes to the DI.

I tested the waste versus RODI water and I am getting less than a 2:1 ratio. It is more like 1.5:1 ratio of waste:RODI. So bad membrane or bad flow restrictor that is letting too much flow? Maybe it is just a $6 restrictor I need to buy.

3. The restrictor could be the problem I guess. But it is a 550 flow restrictor I bought from BRS and it is places in the correct direction.

I almost want to part this RODI system out and just get a Spectrapure unit with upgraded filters because I will know all restrictor a and such are correct.

 

[jedimasterben]

I would highly recommend better prefilters. Use one 0.5 micron sediment filter followed by one 0.5 micron carbon block, and that's it. 10 micron and 5 micron let so much gunk through. For a membrane, look at Spectrapure's treated Dow-Filmtec membranes, they have better rejection and better performance. Also, if you're running one canister of cation and one canister of anion, that's really single-stage filtration. I would run two mixed-bed resins. Again, Spectrapure outperforms the competition. Running mixed-bed resins will extend the life of the second resin and ensure that you are always at zero TDS (of course, providing that you can figure out what is going on that is causing your RO membrane to fail ).

 

[AZDesertRat]

I suspect either your membrane is not seated correctly, you have a bad seal between the housing and gasket or O-rings or the housing has some hairline cracks that are not easily visible but are leaking around the membrane. The membrane does push in much further than you think it does. A little food grade silicone grease on the seals and O-rings helps here.

Are you sure you have the correct membrane for your housing?Some systems such as some Watts Premiers, Sears, Whirlpool and a few others do not use the standard Dow 18-12 series membranes.

Do you have any photos of your plumbing?

Have you ever attempted to blend of mix hot and cold water feeding the system? This can damage a membrane in a heartbeat.

Measure your exact waste ratio using a measuring cup and clock or watch for exactly one minute from the waste line then the trated line and tell us what those exact numbers are. If you really have 1.5:1 you are in trouble as the membrane is not being properly flushed while in use. If you do not have softened wate rand lower than normal TDS then your waste has to be at least 3:1 if not 4:1. If you have soft water and low TDS then 3: and if both are very low maybe 2:1 at the very bottom end.
This is where Spectrapures capillary tube flow restrictors shine, you can set it exactly using your water conditions, not fixed like most others.

I would recommend Spectrapure's 90 GPD over the 60 GPD, the cost is the same and you will get the same quality water much quicker. I would also suggest springing the $52 for the new 99% tested version rather than the old 98% version, doesn't sound like much of an improvement but it makes a big difference: SpectraPure's new 99% Rejection Membrane, your potential cost savings explained... - Reef Central Online Community

 

[ChrisKey]

I have only run mixed bed DI resin until about 3 days ago when I recharged it. That is when I split it, so it would be easier to recharge it next time and not have to separate and split it. I read it isn't quite as effective as a mixed bed but if the membrane would do its job, it would only have to reduce 1-2ppm at most.

I have a replacement housing from BRS and I am using a dowtec filter so they should be compatible. I have pushed it in with all my might and so I thing it is seating correctly. I can use some lubricant and try again but I pulled it out and reseated the membrane 2 times this morning.

I think I will either spend the $130 on a refurbished unit or get a new membrane and housing from Spectrapure. Heck, I have already spent $90 on replacement membranes and so resin every month.

 

[ChrisKey]

I guess it could be seated incorrect or a problem with the housing, but the reason I shy away from that is the filter was reading 0TDS for at least the 1st week. I have a Digital Inline TDS meter and I click on it every time I fill up my ATO reservoir to see how it is filtering. The first week was perfect and then I assume it started to drop off.

I can try to reseat it in a different housing I have and hook it up. I have checked all the tubing and they are correct and in order from prefilter, to carbon filter, to second carbon filter, to RO, to DI, to DI.

One other interesting note is the prefilter and carbon filter have been used for about 2 months and the prefilter is as white and when I bought it. Maybe if it is not filtering anything out, then it is clogging or causing the RO membrane to fail. Could the ouput of RO water increase if the RO membrane is clogged and not allowing any water to permeate through it?

 

[Velodog2]

Forgive me if I remember incorrectly but didn't you say that you were also going through DI resin quickly? When you say that you are getting 0 TDS for the first week I know that isn't after your RO and before your DI. I has to be after the DI. And in that case could the DI be carrying the load of purification for that short period of time, and exhausting itself quickly?

 

[AZDesertRat]

You really need to post some pictures of your RO/DI and plumbing so we can make sure the lines are correct. It is easy to plumb incorrectly and I have been known to do it myself. Also the exact measured waste ratio, we often overlook this important piece since many waste lines are under the sink or stuck in a drain out of sight. Membranes must be flushed continiously when in use, there is no getting around that. it is better to err on the too much waste side rather than not enough, I used to run as high as 6:1 here in Phoenix before I had a water softener and with our high TDS and still would only get 150 gallons out of a DI refill and 18 months out of a new membrane.

If the sediment filter is not filtering anything then it is fouling or plugging the pores in the carbon block so it renders it useless at removing chlorine and toasts the RO membrane quickly since chlorine actually melts the TFC fabric. Usually when a membrane goes bad it fould and the GPD drops way off. In the case of a rupture or chlorine getting to it the GPD can go up as well as the TDS. Measure your flows treated and waste flows for exactly one minute and lets do some math. You also need to know your exact pressure, water temperature and tap TDS and we can calculate almost exactly the flows you should have under those given conditions.

 

[ChrisKey]

This is a coralife filter, so yellow line into sediment filter (1micron, I thought it was a 10 micron but it is a 1 micron) exits the back and enters the back of the second filter (1micron carbon), exits the front and enters the back of the third filter (1micron carbon). I pulled each filter and verified the direction. It pours into the outside section to get filtered and exit through the center section to go to the next filter. Then after the second carbon filter it exits the front up to the auto shutoff valve to the IN section opposite of the screws per BRS recommendation. Then out the bottom (same level as the input) and in the RO membrane 75gpd Dowtec. Top output (white) is going to the manual flush valve and the 550 flow restrictor then out to waste. The bottom output from the membrane is going to the auto shut off valve on the side with the screws, then out to the DI Chambers (entering the right side of the filter DI chamber). This line is where I measure the IN reading on my TDS meter. The to water goes through the 2 DI beds and outputs to my RODI storage. This line is where I measure the OUT on the TDS meter.

TDS Tap = 97
TDS In = 64
TDS Out = 68
Temp of water is 68
I don't have a pressure gauge on the system to see the true pressure, but the pressure of the house is 65 psi, so it should be very close to that.

Waste water 1 1/8 cups per minute
Filtered water 3/4 cup per minute

Using the conversion of 1 cup per day = 90 gpd, the waste is 102gpd and the RODI is 68gpd. That is a ratio of 1.5:1.

I find it interesting that the RODIgpd is so close to the membrane.

I seated the to membrane again and also moved it into a different membrane housing and the readings were exactly the same.

One thing I did notice is the carbon filters don't completely deal so there may be some creep from it where chlorine in the water is bypassing and killing the to membrane.

 

[mrcoffee2]

I had the same problem. The gasket was not seated correctly on my membrane. Once I fixed it my TDS went from 60 to 000

 

[ChrisKey]

I had the same problem. The gasket was not seated correctly on my membrane. Once I fixed it my TDS went from 60 to 000

Thanks. Since the filters aren't close to dirty, maybe my local water is pretty clean for tap since it is around 100ppm and I will stick with the filters.

Maybe get a new .5 micro carbon filter and see if it will seat and seal in the filter. Does the carbon filter in your system form a complete seal or does it have a little movement?

I am thinking I will go with a new 90gpd membrane from Spectrapure with a new flow restrictor and get an inline pressure gauge. Then go from there.

 

[AZDesertRat]

I think you answered you own question with in your last sentence. If the carbons are not sealing and chlorine has gotten to the membrane it is shot, TFC membranes cannot take much if any measurable chlorine. A low range chlorine test kit would confirm this.
Total Chlorine Test Kit w/10 tablets

You should notice a very apparent indentation on the top and bottoms of the carbons where they seat against the canister sump and lid. Some filters need a thick black rubber gasket to achieve a seal.

You appear to be plumbed correctly following this diagram:
http://spectrapure.com/huds/4-STAGE-DWK-RODI-NAG.pdf

 

[mrcoffee2]

Also you may be able to flip the gasket over. That should give you a nice level seal

 

[ChrisKey]

Any idea where to get a thick gasket? I can't find anywhere online.

I do have some spare filter cartridges so I may have a thicker one or I could double the gasket on top. I know that isn't ideal but I could glue/seal them together to prevent the problem. Maybe a new set of carbon filters from Spectrapure will be long enough or have a larger sealing gasket that it wouldn't be necessary.

 

[AZDesertRat]

Over the years I have found some cartridges and some canisters, lids and sumps do not seal well. I always keep the rubber gaskets off of my old cartridges when I throw them away for just that purpose.

 

[ChrisKey]

I didn't try any different seals because I am waiting for the new filters I ordered to come in but I found some black ones on some spares that are probably thicker just in case.

Thanks for the help and information and I will let you know how it works after getting my shipment from Spectrapure.