Omnipure K series, K5654-JJ. Looking for comments

[Reader90]

Hello,

First time posting, long time follower of this thread. I replaced all water conditioning equipment recently to include a softener and carbon filter (whole house) + a RO undersink system. Very pleased mostly with the results.

However, I ran across this filter, Omnipure K series, K5654-JJ (there are a few other variations, connector/size). What interested me was it is a (or claims to be) a softening filter. It interests me to try adding this to my existing RO undersink system as the water coming to the cold kitchen sink is NOT softened.

I cannot find anything out about this cartridge from the omnipure web site, as they list specs on many of their filters, including the K series. However, this cartridge is not listed.

I know there are a few dealers/distributors/experts on this site. I ask you, respectfully:

1. Is this a real filter from Omnipure?
2. Comments, opinions on effectiveness and how long between changes? My water is ~21 grains hard. I assume this type of filter would not work very long as I understand the resin needs to be back-flushed (like my softener I have) every couple of weeks (or based on water consumption rates).

Thanks in advance.

 

[ditttohead]

It is a softening filter but don't bother with it for pre-treatment to an RO. It has a very limited capacity and will likely only last a short amount of time. RO systems can handle hard water. Worst casr is your membrane may have to be changed every year or two instead of every 3 to 5 years.

Dallas! I will be there in a couple weeks at the TWQA convention!

 

[Sponsor]

 

[Reader90]

Thanks for the feedback. Thought so -- i.e. would not do much and would need to be changed often to stay effective. And, safe travels to Dallas area!!

My issue is, which I should have started out by stating, with the TDS values I am seeing with the new RO system I installed as compared to the one replaced. Doing more homework on the Internet (yep, I am also part of the "peanut gallery" here), the other "difference" between this RO system and the older RO system I replaced was the introduction of a permeate pump. I have seen articles on "TDS Creep" and much discussion around the introduction of the pump into an RO system.

This article (with animation!!) is interesting. I have also seen other articles stating the same behavior:

http://www.purewatergazette.net/blog/tds-creep-with-aquatec-permeate-pump/

What is interesting about this article is it discusses measurement of the performance of the RO system, expressed in % of rejection -- which I understand to be performance related, i.e. how much TDS is removed as a calculation of TDS before entry into system and TDS amount at exit point. a hypothetical 0 (zero) TDS would be a 100% rejection rate, which is not achievable for I assume many reasons. But the RO filters on the market, along with various articles discuss "in the 98/98%...." range, +/- from those numbers based on factors such as PSI, temperature of water, etc.

However, my setup is producing ~80% +/- a few points, rejection rate. Not very good IMO. My TDS measurements of RO water are in the range of 45 (low) to 70 (average) with the TDS going into the system at ~550 +/- ~1/2%. At these numbers, my system is rejecting ~88% to 91% -- no where near the 99%, but lets say 95/96% should be realistic (with PSI and temperature not optimal), i.e. 15 to 20 TDS?

My setup i think is correct, as I helped my plumber install the system following the instructions. This is my setup:

City Water IN --> Omnipure Q5605 --> Omnipure Q5621 --> Omnipure Q5621 --> Pentair GRO 50EN --> Permeate Pump Aquatec ERP 500 Omnipure --> K2533KK --> Tank/Water Faucet/Ice Maker

Other Data:
Water Temp at cold kitchen feed = 66 degrees F
Water pressure = 48 psi

Other things I have tried:

1. Empty water tank, shut off water supply.
2. Turn on water supply. Measure within 5 mins. Still seeing ~70 TDS, with same City water ~550 TDS
3. Changed all filters/membrane @ 7 months (and did #1/2 steps a few times).
4. I bought another TDS meter to confirm my readings -- no difference.

Other things I am considering:

1. Remove permeate Pump (though I will miss the increased flow rate from RO faucet!!)
2. Add ASO valve.

I like my water, tastes good (and whole house system is great and soft!!). However, I would think this RO system should be doing better than what I am seeing/measuring.

Thanks for any thoughts, comments or suggestions in advance!!!

 

[Bannerman]

As the Pentair GRO 50EN membrane requires minimal drain flow to flush away contaminants, apparently, a permeate pump does not produce the same benefits as when used with a conventional membrane. You may wish to remove the permeate pump to re-evaluate the performance of the system.

 

[ditttohead]

The GRO and Permeate Pump are not a great combo... too much technical stuff to explain outside of a classroom setting...

A few items, the ASV is not typically recommended though we do sell a ton of them (90% / 10% shutoff version) they are typically not needed except in very low usage applications.

When using the permeate pump with the 50 GPD GRO membrane we seem to have good success when we us a much larger flow restrictor than the recommended 150 ml/min. Increasing that to 350-450 tends to help a lot.

The GRO membrane is an ultra high efficiency membrane, as you know nothing is free. One of the sacrifices with getting an ultra efficient membrane is that you will get slightly lower rejection.

Test your membrane exactly as follows to determine the membrane rejection.

Turn off the tank, open the faucet, and remove the line from the permeate out of the permeate pump, let this run for 10 minutes then test this water after it has run. This will give you an accurate assessment of what the membrane can do.

TDS creep is caused by the natural process of osmosis. On large commercial systems where higher purity is needed we flush the back side of the membrane with high purity water (permeate flush). Since a PP operated system tends to cycle on and off every time you use even a small amount of water, the water that has been able to osmose into the membrane (this is concentrated brine) that water will go to the tank thereby raising the tds. A system with an ASV cycles much less frequently so the same process occurs but you tend to have far greater dilution of this lower quality water so the creep is not as bad. Assuming you simply use more water, this will tend to nearly eliminate the noticeable "creep".

Complex topic, hopefully I explained it so that is understandable without going into it too deeply.

 

[Reader90]

Thanks for the replies on this topic. I will do testing as dittohead describes. Will get back to this thread in a few days once I have been able to complete the tests.

 

[Reader90]

Hello All. Did some testing. Short response to outcome following following steps:
1. Turned cold city water feed to RO system off.
2 Open RO faucet --> drain tank
3. Turned tank off.
4. Turn cold city water feed to RO system on.
5. allowed RO water to drain (slowly). Measured in cup TDS at:
5 min: 33
10 min: 42 (see note below)
11 min: 24
15 min: 19
20 min: 14
25 min: 14
30 min: 14
6. Closed RO faucet.
7. Turned tank valve on.
8. Walked away for 2 hours
9. Measure RO water at faucet after 2 min run: 44 TDS

NOTE: Wife came to kitchen and washed hands, turning on normal kitchen city water while I was filling glass at 10 min measurement. I noticed the pressure of the RO faucet slightly change when water was turned on/off (so slight, assume it changed the pressure -- just like when one is in shower and sprinklers turn on or a toilet is flushed). The measurement was 42 TDS.

Do I have normal city water making it into my RO water randomly during the regular kitchen faucet turning on/off, thus impacting the water pressure and impacting the permeate pump seals or mechanics. Or, is my overall water pressure from my city bordering on the low side for the RO system/membrane to work efficiently and replacing the permeate pump with a water line booster pump/regulator switch be an approach I could consider? Or something else to consider (besides doing nothing).

Again, thanks in advance.

 

[ditttohead]

Not much to add to what I wrote above. PP and GRO do not play well together unless you increase the Drain Flow Restrictor, that's about it.

 

[Reader90]

Thanks for the response. The current Drain Flow Restrictor in the system is a green capillary style flow restrictor, 525ML/MN (GREEN) FOR 50GPD Membrane. Came with system.

Not sure I understand last comment. Would "increasing the Drain Flow Restrictor" mean a larger restrictor that allows more that 525 ML/MN?

Any validity in idea to increase inlet water pressure into the RO system as my home water pressure is less than 50 psi (e.g. Aquatec 6800 booster pump + adding a pressure shut off valve) ?

If anyone can recommend a water specialist dealer I can talk to and discuss my RO situation along with procuring needed parts or designing/ordering a new system, I would appreciate it.

Thx

 

[Bannerman]

Ditttohead is one the most experienced and knowledgeable on this site.

From post #5 above: "good success when we us a much larger flow restrictor than the recommended 150 ml/min. Increasing that to 350-450 tends to help a lot."

As you now specify your RO is equipped with a 525 ml/min restrictor, it appears the supplier of the system had installed the restrictor normally utilized with conventional 50 gpd RO membrane, perhaps to compensate for the permeate pump.

 

[ditttohead]

If you want to increase performance without replacing the whole system, the best way would be to either eliminate the Permeate pump (not my preferred way) or to replace the membrane with a more traditional higher rejection style. Adding a 90% shut off may help as well but again, not what I would recommend.

A traditional membrane can have as high as 98%+. Please be ware this is a laboratory rating and not a system rating. When we run these numbers it is done under repeatable controlled conditions so that we are able to compare different membranes based on the same factors so the comparisons should be fair. The GRO membrane is an ultra high efficiency design but it does lack the ultra high rejection that a traditional membrane can provide.. Everything in water treatment is a compromise.

I sent you a PM.

 

[Bannerman]

The GRO membrane is an ultra high-efficiency design but it does lack the ultra high rejection that a traditional membrane can provide..

As the recommended 150ml/min restrictor has been replaced with a 525 ml version, it seems the largest benefit for using the GRO membrane has been lost. It appears the greatest benefit to GRO is when operating without a permeate pump.

Since using a traditional membrane will result in higher rejection, and using a permeate pump will provide faster recovery and more efficient membrane function, I then anticipate the average total daily volume of water discharged to drain will remain reasonable, considerably less than a traditional membrane without a pump. While there may be somewhat higher drain flow while actually operating compared to the GRO without a pump, I suspect that would be a fair tradeoff overall to achieve the highest rejection rate possible while also realizing the efficiency benefits of a P pump.

 

[ditttohead]

Nicely put!

I tend to overthink it sometimes and put in too much information but... beautifully and simply stated.

As an adder, a permeate pump can provide better rejection since it hides the backpressure from the tank giving the RO a higher differential pressure.

But... due to the short cycling a small amount of "less than perfect" water will go to the tank if only small quantities of water are drawn regularly. Simply use more water, problem solved.

Now the theoretical math...

A GRO is set at a 1:1 ratio, but this is when the tank is empty and there is almost no backpressure so the differential pressure and thus the production rate is at its highest. When the tank fills the differential pressure decreases which slows the production (not the waste) so the 1:1 ratio decreases.

A normally sized permeate pump is set at approximately3 or 4:1 ratio, but since the backpressure from the tank is effectively hidden from the mebrane production, the permeate is consistent regardless of how full the tank is, so the ratio is consistent from beginning to end.

A permeate pump also has a nice advantage of filling the tank to nearly line pressure compared to just 60% maximum of line pressure.

Sorry, lots of information here but this is not the simplest topic especially when comparing the system efficiencies.

 

[Reader90]

Update:

1. Turned water off to RO system.
2. Emptied RO tank through faucet.
3. Turned water back on to RO system. Let water run through RO faucet for 30 mins (dripping), and tested TDS 3 times within 1 or 2 mins. 16/14/15 TDS readings. This is consistent with the measurements from last round of testing a few days ago.
4. Turned water off to RO system.
5. Removed and replaced the RO drain line OUT, green 525 ml/mn capillary style-restrictor valve with a 110 ml/mn inline-style restrictor valve.
6. Turned water back on to RO system.
7. Tested ~4 hours later - 35 tds. Tested ~24 hours later, 34 TDS.
8. Tested ~48 hours later, taking two samples. a) immediate from opening faucet and b) let faucet run for 30 seconds. a - 55 TDS b - 34 TDS.

So, I think I have this system working to specification based on my conditions. I am happy with the results with this change. I will continue to monitor and report back. Perhaps I can tweak with an ASO valve and/or removing permeate pump. Not sure it will make that much of a difference at this point. I still

Other thoughts/comments:
1. Apparently, this is the recommended type/size of drain restrictor valve from Pentair as per their website, and subsequent pdf spec sheet. Also found similar info here: http://www.purewatergazette.net/blog/gro-membrane-retrofit-march-16-2016/. Not sure why the kit I bought came with the green capillary 525 ml/mn, assuming a mistake was made and/or was sized for a "traditional" RO membrane, which still seems on the high-side.
2. After this experience (mine), not sure I would recommend the combination of the Pentair GRO membrane and a permeate pump. If I did it all over again, I would go with a traditional style RO vessel/membrane for that stage of the system. I love the other filter types (Q series from Omni Pure) as they are SO EASY to replace. The additional pressure from the permeate pump is nice too!!
3. Perhaps I can tweak system performance by adding a ASO valve and/or removing permeate pump (try both combos). I also am not sure if increasing water IN pressure would improve performance. In the end, not sure it will make that much of a difference at this point, as 32 - 35 TDS is much better than what I was getting before the restrictor valve change (but, not as good as my previous Watts RO 5S system without permeate pump).
4. Also, I might test a traditional style RO vessel/membrane/new sized restrictor valve at some point in the future.

Thanks again for all comments, suggestions from dittohead and bannerman!!