RO membranes
 

Recently purchased a 50gpd membrane to replace my 100gpd, as I read and/or someone told me they were much more efficient.

It makes half or less ro water then the 100 did, thats for sure but almost the same amount of waste water. How the hell is that efficient. What a poc. Plus cant get a 0 tds reading on the new membrane. Still reads 6ppm, a couple weeks later.

AArrggggg.

the 150 has the highest rejection rate (here)

sucks about the still high TDS

did you replace the flow restrictor along with the membrane?
I heard you had to do that.

No I never. No idea I had to. Just reading the link from BRS. What does that do when replaced and not replaced?

Thanks for the link Mark. I thought we discussed it somewhere before.

The flow restrictor is matched to the membrane to provide the best waste to good ratio along with the lowest TDS for the particular membrane. That will explain why you're producing as much waste with the new membrane as with the original 100 gpd, but only making half the amount of good water. It's kind of like your system is on a permanent 90% flush, with much of the water bypassing along the outside of the membrane. It's also likely why you're experiencing a higher TDS at the moment. Should be an inexpensive fix, restrictors are not that costly. I believe there are even adjustable restrictors available these days.

Mark... I thought the 75 gpd was one of the most efficient membranes?? Is the 150 two 75's in series?

Alrighty. Thanks Mike. Great info. Now to find a flow restrictor. Hope thats easier than finding critters for a sand bed in these parts of the country. :lol:

Finally found some 50g flow restrictors at JL. Now I need to find more things to order. :lol:

So, where is mine? No where to be found on the waste water line. Is it in the bypass valve somewhere?

Ok. Cant find it anywhere. New 50gpd on the way from JL.

Some systems have it integrated into the fitting on the outlet of the membrane housing I think. Mine is quite obvious since it's a combination restrictor/flush valve and installed separately on the waste line. Not sure what your fittings look like, might be marked on the fitting itself if you look more closely. If you don't see anything beyond the fitting on the membrane housing, you might just need to replace that with a new, conventional elbow or something. Good luck.

I find the best flow restrictor to be a ball valve. With a PSI gauge on the input of the membrane you can adjust the ball valve so that the pressure on the membrane is to spec.

The 150gpd may have good rejection rate but needs 65psi to the membrane in order to acheive this. Most city homes will not have this kind of pressure and a booster would be needed. The 75gpd is the most popular membrane because it also has a high rejection rate that only needs 50psi to acheive which is great for most city homes and you would not need a booster to reach 50psi.

Restricting the flow before the membrane is unlikely to correct a problem of mismatched membrane/flow restrictor downstream of the membrane. I could be mistaken, but I'm not sure a ball valve will lower the psi that the membrane sees either, all you do with that is restrict the volume of water available by making the opening in the line smaller, the same psi will still be present. If you're on city water and wish to adjust the water pressure, you may be better off locating the PRV (pressure reducing valve) in your home's plumbing. These are requred by code in most municipalities and I believe the default setting is 50 psi. They are adjustable though, and I've adjusted mine to provide around 80 psi.

I never said I restrict the flow before the membrane. The ball valve goes on the waste end of the membrane and the PSI gauge on the input. When adjusting the ball valve you will see the PSI on the gauge go up and down.

Never heard of the PRV before...I will look into that.

Ah so, sorry, I made an incorrect assumption there when I saw the part about the PSI gauge on the input. My bad.

PRV should be fairly near your water meter, just downstream, although mine is quite a ways down and my outdoor tap is plumbed in before it to take advantage of full city pressure for the garden.

http://www.plumbersurplus.com/images...-5734-3809.jpg

Thanks Mike. I also have a separate flush valve. Thats why I figured it was in there but dont see something that resembles it, unless its inside the valve.

My flow restricter is in the waste water line ( tiny insert) just at the waste output of the membrane

Yes, thats where I thought it was. But be darned if I can find it. Still thinks its part of the flush system.

in the Aquasafe the restrictor is part of the flush valve, make of your unit?

I think it's safe to assume your restrictor is in the flush valve, after all, isn't the purpose of the flush valve to bypass the restrictor? Makes sense that it's integrated. Not sure the restrictors in flush valves are easily replaceable though, you might have to replace the whole flush valve unit with one having the appropriately sized restrictor for your new membrane. Otherwise you could simply remove the entire flush valve when the new restrictor you ordered comes in. You could still flush the system from time to time by reinserting the valve assembly, usually pretty painless with the quick disconnect JG fittings. Or just have the restrictor at the very end of your waste line and pop it off to flush. Or a T-fitting with ball valve before the restrictor, there are a number of solutions, as you can see.

I dont recall the name but sure its on one of my cd,s on the proper connect. I bought it from Prairie Reef Supply in Winnipeg, when he was still in business.

Thats sounds like a great idea, since I already order 2 of the 50 gpd from JL. I think thats exactly what I will do. Thanks you for your assistance. You guys are what makes Canreef the best. :smile:

the 150 your talking about is that the Dow 100/160? I run two of these in my RO unit, they put out 100gpd at 60psi, or 160 gpd at 90 psi. exelent membraines.

Steve

Yes I'm talking of the dow filmtec membranes (the best IMO).

How ever I only know of the 50,75,100 and 150gpd membranes. Never head of the 100/160?

almost all of them are variably rated, one rating at 50 psi a few years.
back unsaviory vendors were using this to there advantage and not telling people, so they would sell the 75@60 as a 90/160 , as at 60 PSI it is a 90gpd and at 100 PSI it was 160 GPDand it was cheeper than buying the 100 which would give you a true 100@50psi. then they would blame the lower output on the temp of your water.

since the membrain is rated for up to 150 PSI this wasn't a problem as long as people knew what they had and that at 50 PSI they only had a 75 gal membrain. another company started relabling dow 75 and 100s as 100/160's at 50 and 90 psi, but it was a dow membrain just relabled. mine are dow 100's which I run at 120 PSI giving me a total output of more than 360 GPD when I measured it last. I ran them this way for 2 years and did a 5 min backflush after every use, but they have been dry since I moved now so I will have to buy new ones.

Steve

hmm so you are using a PRV as a flow restrictor after your RO? to me that doesn't make sence as an adjustable PRV is about 75 bucks where a ro restrictor is 1.00.

I spent 5 bucks on a needle valve and used it to adjust my inlet PSI but I run two membrains in parallel

Steve

NO he mentioned the PRV as something someone could adjust to get your house plumbing at a higher PSI. The PRV is located near you main shut off I guess (still havent went looking for mine).

As for the GPD ratings being multiple on Dow membranes, when I look at the dow filmtec membranes are not sold like this. I believe that virtually any ro membrane will produce more GPD when higher pressure is applied. The problems with doing so is that the rejection rating will be affected. If you want rejection ratings similar (I actually find them better) then advertised then you should run them to spec.

ah, ok.. I never had one in my houses. I had to install one in the first house as they jacket the PSI, but my PSI in the second house sucked so I had to buy a booster pump.


DOW never sold them this way, it was a company who was buying dow mwmbrains and relabling them as so many GPD@60PSI and so many @ 90 PSI. the rejections rates are constant through out there operating range as Dow is giving a minimum operating spec. I installed several systems over the last 8 years (comercial and non comercial) so I have had to talk to DOW directly on a few of the aplications and what I got from there engineers was that the rejection rate won't change untill the membrain starts to break down. so if you operate it in a way the is dammaging then you will get degraded preformance. operating at 100 PSI wont cause this, operating at 150 might start to as that is its upper end. at any rate I was confadent running my own at 120 PSI with a high volume pump to suply the water (only had 40 PSI at the second house) so after two years the output was still "0".

Steve

Well I have to ask then. If all it takes is more pressure applied to the 75gpd membrane and it will produce 150gpd with the same rejection rating then what is the difference between the two membranes??

the amount they will put out at the industry standard of 50PSI.

Steve

The dow filmtec 150gpd is spec'd at 65psi input. Anything less and you will not get 150gpd.

Take a look at the specs sheet posted at BRS. I will attempt to post it here but don't know if it will like hot linking.

http://www.bulkreefsupply.com/store/...f/i/file_4.gif

um, DOW doesn't make a 150, they also don't make membrains that the part number starts with TF. the DOW membrains that most of us use are
TW30-1812-GPD (24,36,50,75,and 100)

so you have managed to show a info sheet for a non dow product.

Steve

You guys have made this a thread full of info. :D Good reference for the future.
My new restrictors came in today. Going to pull the bypass and install one in the line. Guess I will just have to put the bypass in to use. At least until I use up this membrane.

Bah, no one will see this in the future, if they would, they would have found the threads from 8 or 9 years ago with all the same info :mrgreen:

Steve

I will. And yes, I never searched for past threads as I had a specific question. Did you read it?

As its my thread, I will check it for reference info in the future. Going to search the others now and see if the same info that helped me with my problem was mentioned there, not all the discussions you two had, half of which I dont have a clue what you,re talking about. :lol:

Besides if everyone just searched, we would have no discussion :lol:

true, thats why I try not reply to people with do a search. I was just letting you know there is a lot of info on ro's from discussions we had when the board was young if you wanted to look them up also.

Steve

I was young then also. Now that I,m old I cant look stuff up very good anymore. :lol: :lol:

Apparently I did. I didnt realize that the 100gpd and 150gpd membranes that BRS sells are not dow filmtec. I got that spec sheet from their website.

How ever my understanding still is that all membranes must be used at the spec pressure to achieve the best rejection rate. You can up the pressure but you will see a decrease in the rejection rating.

You are right that all dow membranes are spec at 50psi. The 100gpd has a poorer rejection rating though, and they don't make a 150gpd.

there may be a slight decrease in rejection rating, but it is not one that would be measurable and definatly not enough to be worried about.

we routeenly installed systems which were intended to make drinking water from untreated water and we would set them up at 100PSI. send in water samples and they would come back just as good as the plaves that have lower pressure. We also checked with DOW engineers befor setting them up this way. what we were led to believe is even at the max operating PSI of 150, the DOW filmtec would still have a better rejection rate than other brands. now this was about 8 years ago so who knows the quality of the copy brands now.

Now from running my own RO, at 50 PSI I get 0 PPM out, at 125 PSI, I get 0 ppm out. now that was with between 20 to 60 PPM in (depends on time of season)

Steve

Update. Removed the bypass. Installed the restrictor. It has increased the ro output, at least as much as a 50gpd can and has decreased the waste water some but, IMO, still makes to much waste water to ro water ratio compared with my 100gpd, which are the only two I have experience with.

remember if you don't have enough waist water it will cause your membrain to plug faster. ideal is 4 to 1, you can get away with 3 to 1

Steve

:question:
Doing at least 4 to 1 Steve. If not more. I,m going to do a measure perhaps.