RO/DI Question, Defective New Membrane?

[HowardW]

I just changed all my pre filters and upgraded my membrane from the Filmtec 50gpd to a new Filmtec 75gpd with a new membrane housing and 75gpd flow restrictor and am having a problem.

My tap TDS is right around 300 and my previous post membrane TDS with the old 50 gpd membrane was right around 11. I flushed out the new catalytic carbon and carbon block pre filters for about 15 minutes and then installed the new membrane and flushed out the first 10g of water from that, and no matter how much water I flush I cannot get the TDS under about 25-27 TDS and it now also spikes up to the high 30s and then comes down to the 20s after a minute or two. I was also careful to fully seat the membrane into the new housing.

Any ideas?

 

[Randy Holmes-Farley]

My only idea is that perhaps it is not installed correctly and is leaking. I suppose the TDS measurement may also be faulty.

 

[old salty]

Water pressure and temp play a significant role in the efficiency of the RO filter. Beings that you are located in Illinois, I would assume your water temps are much lower now than the summer. Any idea what your water pressure may be?

 

[HowardW]

My pressure to the membrane is at 44-46 psi and the temp around 74-76, same as it was with the old membrane.

I may try unscrewing the membrane housing and pulling out the membrane part way and try pushing it in again and see what happens?

 

[Billybeau1]

Yes Howard, sounds like the membrane isn't seated correctly. If you continue to have problems, holler back. We'll get you some help.

Also it takes some time to flush a new membrane. Not sure how many gallons but 10 may not be enough.

 

[mrgettanked]

<a href=showthread.php?s=&postid=11544612#post11544612 target=_blank>Originally posted</a> by HowardW
My pressure to the membrane is at 44-46 psi and the temp around 74-76, same as it was with the old membrane.

I may try unscrewing the membrane housing and pulling out the membrane part way and try pushing it in again and see what happens?

The manufacture adds a protective coating on a new membrane and you should flush for at least 20 to 30 minutes depending on your PSI reading and water temp. The lower the PSI and the colder the water temp is, may require extended flushing time.

Good Luck!

Garry

 

[AZDesertRat]

How the heck do you get 74-76 degree water in Illinois? Mine in Phoenix is only 58 right now!
Calculate your waste ratio with a measuring cup and clock to see if you are close to 4:1.

 

[HowardW]

<<< How the heck do you get 74-76 degree water in Illinois? >>>


Because I have the unit hooked up to a 'Y' off the basement laundry tub faucet so I can adjust the water temp.

 

[AZDesertRat]

Bad idea!!! Do not try to blend hot and cold or you run the risk of melting you membrane in a heartbeat.

All it takes is one flush of the toilet or someone taking a shower to change the available pressure and delivery at that faucet and you are done for. Have you ever been in the shower and someone flushes the toilet or starts the washing machine and you either get scalded or frozen??? It is not recommended .

With this bit of information you may have answered your own question, your membrane may be toast already. It only takes a few seconds to melt membrane fabric.

 

[HowardW]

Yes I know about that. We are very careful not to turn on any cold faucets or flush any toilet while I'm making water or while the drinking water tank is refilling. I told my wife if she can't wait then I turn off the water to RO/DI for a few minutes.

 

[Billybeau1]

The other reason its a bad idea to use warm water is because the water coming from your hot water tank may contain sediment and clog your filters prematurely. As the Rat said, its a bad idea to use warm water.

My Ro/Di runs just fine with cold water and 45 psi. It just takes a little longer to get water.

 

[HowardW]

I think I found the problem. I decided to disconnect and remove the membrane housing and unscrew the top just to make sure I pushed it in correctly and there was no bypass causing my above normal TDS readings. I've changed membranes 2 or 3 times before without issue but I wanted to check to make sure. I found the membrane was in way to far into the housing when compared with my old membrane/housing. The old one when correctly seated stuck out just a bit from the top of the threads and this one was about 1" inside.

Perhaps either the membrane or more likely the housing is defective which caused the problem.

 

[rbursek]

Water heaters are notorious for collecting and holding heavy metals, causing your membrane and pre filters to clog/work harder then just your cold water.
Bob

 

[AZDesertRat]

What brand of RO unit do you have? Are you using the same model number of membrane each time you change it ? Dow Filmtec has a couple different model numbers with the 1812-xx series being the most popular. Some units like Whirlpool, Sears, some Watts Premier and a few others do not use a standard 1812 series membrane though and even though the 1810 replacements look very similar they are not. The O rings and nipples on the ends are different and will not work.

 

[HowardW]

I replaced the standard Filmtec 1800 series 50gpd with a Filmtec 75gpd and also replaced the housing with the standard white membrane housing sold by the sponsors here.

I thought there was something not right initially with either the membrane or the housing because it didn't seem to push in and seat correctly and it pushed into the housing way too far when compared with my old membrane and housing. My guess is the housing was just defective. The vendor is sending me out a new membrane and housing at reduced cost and that should take care of it hopefully.

 

[AZDesertRat]

1810-xx or 1812-xx series? They are different and can be mistaken.
Hopefully the new parts will cure your problem.

 

[HowardW]

Ooops, meant to say 1812 series, not 1800.