Problems after replacing RO membrane

[Atu]

Hello all, so, after about three years the TDS from my RO membrane raised from about 3 to about 14 (tap water around 180), so I decided it was time to change the membrane.
The problem was my father originally build the system, and I didn’t know the GPD of the membrane. It was a Kent welded membrane, so I also had to buy a case for it.
Luckily, or so I though, a guy in a local reef Facebook group posted a cheap 100 GPD membrane with housing and I went for it.

After two days of filtering water I’m still getting around 70 TDS, and I’m starting to think I did a mistake.
So what I’ve thought so far is this

1) the GPD isn’t the correct one for my system, especially for the flow restrictor
2) the membrane or the case were damaged before I got them
3) I’m doing something wrong

Below the photo of my previous membrane first and then the new one.

 

[flooddc]

I think that cheap membrane is your source problem. Never heard of the brand Vontron. I did not find any spec on it to see what's the rejection rate.

Open your old housing, it's like a 75GPD Dow Filmtec and get a high quality replacement membrane.

Also, a 90 or 100GPD is actually a 75GPD. (75GPD rated at 50PSI while 90 or 100GPD rated at 60+PSI).

 

[Atu]

I think that cheap membrane is your source problem. Never heard of the brand Vontron. I did not find any spec on it to see what's the rejection rate.

Open your old housing, it's like a 75GPD Dow Filmtec and get a high quality replacement membrane.

Also, a 90 or 100GPD is actually a 75GPD. (75GPD rated at 50PSI while 90 or 100GPD rated at 60+PSI).

The old housing is welded, it cannot be opened, that’s the problem.
I’m gonna try and find a good RO membrane for comparing it with this one.
Could I give this cheap membrane any use? Maybe as a pre filtering for the good membrane?

 

[flooddc]

The old housing is welded, it cannot be opened, that’s the problem.
I’m gonna try and find a good RO membrane for comparing it with this one.
Could I give this cheap membrane any use? Maybe as a pre filtering for the good membrane?

Try taking the RO out and make sure you seated in correctly. Hopefully is just that. I have a bad feeling about that off brand membrane.

 

[flooddc]

Also, I had Kent RODI before and replaced the membrane in it before. Use 2 rubber strap wrench.

 

[Atu]

That was my first assumption. I removed the membrane and placed it again 3 times already. It’s really hard to pull out so I think it’s seated correctly. Maybe a rubber seal is faulty thought...

Kent makes different membranes, I think this one is discontinued, it cannot be opened. There are videos in YouTube of people sawing trough it.

No the same model but another welded model.

 

[Atu]

The flow restrictor I’ve has “800” written, might I be using the wrong one?

 

[Water Dog]

In the second picture that you posted, of the membrane and membrane housing, if that is how you have the membrane oriented in the housing, than it looks backwards to me. The black rubber seal on the membrane should be closer toward the fatter screw off end of the membrane housing.

Although I use a capillary flow restrictor on my Spectrapure system, according to this BRS barrel style flow restrictor chart, 800ml seems right for your 100 gpd membrane.

https://www.bulkreefsupply.com/reverse-osmosis-flow-restrictor.html

 

[KStatefan]

I think that cheap membrane is your source problem. Never heard of the brand Vontron. I did not find any spec on it to see what's the rejection rate.

Open your old housing, it's like a 75GPD Dow Filmtec and get a high quality replacement membrane.

Also, a 90 or 100GPD is actually a 75GPD. (75GPD rated at 50PSI while 90 or 100GPD rated at 60+PSI).

In the FilmTec product line the 75 gpd and the 100 gpd are different membranes

BW60-1812-75 75 gpd at 50psi 99% Rejection

TW30-1812-100HR 100 gpd at 50psi 98% Rejection

 

[flooddc]

The flow restrictor I’ve has “800” written, might I be using the wrong one?

http://www.purewaterproducts.com/articles/flow-restrictors

 

[flooddc]

That was my first assumption. I removed the membrane and placed it again 3 times already. It’s really hard to pull out so I think it’s seated correctly. Maybe a rubber seal is faulty thought...

Kent makes different membranes, I think this one is discontinued, it cannot be opened. There are videos in YouTube of people sawing trough it.

No the same model but another welded model.

Then it could be that the new membrane that you put in is defective or poor rejection rate.

I went and dug out my old Kent RO. Looks exactly like yours.
Kent RO by t@#$%c, on Flickr
Kent RO by t@#$%c, on Flickr

 

[Atu]

In the second picture that you posted, of the membrane and membrane housing, if that is how you have the membrane oriented in the housing, than it looks backwards to me. The black rubber seal on the membrane should be closer toward the fatter screw off end of the membrane housing.

Although I use a capillary flow restrictor on my Spectrapure system, according to this BRS barrel style flow restrictor chart, 800ml seems right for your 100 gpd membrane.

https://www.bulkreefsupply.com/reverse-osmosis-flow-restrictor.html

In that picture its backwards, you are right, but thats not how I've it.

Then it could be that the new membrane that you put in is defective or poor rejection rate.

I went and dug out my old Kent RO. Looks exactly like yours.
Kent RO by t@#$%c, on Flickr
Kent RO by t@#$%c, on Flickr

You are right, it does look exactly the same. Im gonna try with a wrench and report back.

 

[flooddc]

In that picture its backwards, you are right, but thats not how I've it.



You are right, it does look exactly the same. Im gonna try with a wrench and report back.

use a strap wrench to hold the housing in place and use a channel lock to turn the nut on top of the ro housing. GL

 

[Atu]

use a strap wrench to hold the housing in place and use a channel lock to turn the nut on top of the ro housing. GL

Well flooddc, you were completely right. I was able to open it and remove the old membrane. Im gonna try the new membrane with the old housing now and viceversa to see if I can find the problem. Gonna report back when I do for future references.
Thanks a lot to everyone!

 

[Atu]

Well, the old membrane was a 50 GPD, so I might not have enough pressure for a 100 GPD.
I replaced the sediment filter and got a 30 TDS reading with the new membrane, and a 6 TDS reading with the old membrane.

It might be that the pressure of my system changed in the last couple of months (we have a pressure pump in the house and a plumber did some work with it some time ago) and that’s why my TDS raised.
Also, the old membrane rubber seal was kind of faulty, I re-accommodate it so that might have something to do with it.
I’ve a tap TDS above 180, so that’s a 97% rejection rate. I think I’m gonna leave it as it’s for now and replace the resin, which is exhausted.
Or do you people think 6 TDS is too much for the resin to handle?

I think a good lesson from all of this is that a pressure gauge would probably help me a lot, I’m gonna check on that.

Thanks again to everyone!

 

[Atu]

So.. funny thing. I replaced also the first carbon filter and the resin.
Now I’m reading between 1-0 after de membrane, and 0 after the resin. I guess the carbon filter and the pre filter were clogged and dropping the pressure. Maybe later I’m gonna re test the 100 GPD to check if I’m getting lower TDS.