How long should 100gpd membrane last

Hello all. any ideas on how long a 100gpd membrane should last on average.
It’s a new system that I have only had running for about 2 weeks. the tds in this area is very high, average reading going in is 550ppm. when I first set it up I had RO in 550ppm Ro out 28ppm and 0 after the DI. I haven’t been makeing anywhere 100gpd, probably about 25 - 30. first week was fine with 0 reading all week but during the last week the reading has gone up to 10 and when I checked the RO out it’s at 50ppm.
Help am I running something wrong. I have been turning system off rather than just leaving it running.

My last lot lasted 10 years, that’s before the Chinese started knocking them out in bulk. I think backwashing, winter storage & pressure may also come into the equation & therefore difficult to discern.

If you backwash the membrane often you can get a long life out of it. Also test you water to see at what reading it spots. I have had spot free glass at 30 TDS

Can you explain how to backlash the membrane

[LEFT][COLOR=#1A1A1A][FONT=lucida grande]Thanks Karl and John, have flushed it a couple of times and John I flicked some that was reading 4ppm on to a pane and it spottted. am thinking that if I put another 100gpd membrane in line it will reduce the numbers.[/FONT][/COLOR][/LEFT]

Thanks Karl and John, have flushed it a couple of times and John I flicked some that was reading 4ppm on to a pane and it spottted. am thinking that if I put another 100gpd membrane in line it will reduce the numbers.

How long should 100gpd membrane last? I am assuming you are talking about an RO/DI unit…

Membranes should last 3 to 4 years, or more! Depending on the usage. Don’t be fooled and make the same mistake I did…
My TDS output readings started climbing from 00 to 01,02,03,05,13 on a 2 yr. old RO/DI unit. Replaced the 10” 5-micron sediment filter cartridge and carbon block filter cartridge… It lowered TDS a tad…

Went to Aquatica in Tinley Park, IL… Inquired about DI Resin for my refillable DI cartridge and possibly replacing my 100gpd Membrane. Was told that the membrane should be replaced about every 2 yrs. or so and recommend replacing it.

Purchased both items from them… The quality of the color changing DI Resin was superior and at a comparable price. On the other hand… The membrane ($99.99) was marked up at least 200 - 300% compared to on-line prices ($27.50) for the exact item.

Installed the membrane and changed DI Resin… Ran unit for about 3 hrs and my TDS came down to 00. Great!

The next day, thought I would do a switch on the membranes, putting the old one back in. Ran unit and to my surprise, the TDS remained 00 and same flow rate as with the new one. Then found out these membranes should last at least 3 to 4 yrs., or more… depending on use.

So… Change the DI resin, Carbon Block and Sediment cartridges first. If your unit does not have a TDS meter, I strongly suggest you invest in one.

My unit:

If you need to, purchase your next 100gpd membrane here:

What type system? Mine is a 150 gpd but usually run only 75 gpd. Depending on TDS and flushing they can last for years, depending how much water you run. Could go 2 years then. Depending on the type RO filter they are not expensive 40-100. If you are not running at a good , lets say 65 psi could be a problem. You have 1 RO correct? Mine is a 150 so can disconnect 1 to make 75. Check out the aquarium forums or call/email a place like BulkReefsupply. They can figure out what is wrong. Might need a better quality RO filter. Worse case if it is the high TDS you may need a bigger DI because the small DIs on these system last if a few ppm coming in. Once you get bad RO the DI will burn thru pretty quickly. I sometimes run thru my 1/4 cube. I have a few buddies around here that have bigger systems than mine. Let me ask them what they think.
He is out of the field and will go see in a day or so. 1 thing, if adding another Ro you really need to find out at what psi you need to be at. Tap pressure is a bit tough to push 2 100 gpd ROs. You may need a pump to get full psi to run 2 100s unless a low pressure type.