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georgec
08/29/2013, 08:33 PM
Hi,

I have a typhoon reef keeper filter. Just replaced all the filters and DI because it has been a while.

My question is: How often does the membrane need to be replaced?

Before I replaced the filters, I was getting 0 TDS out (22 TDS in). Still getting 0 TDS out after replacing all the pre-filters and DI.

Is there anything reason to replace the membrane? (I bought a spare with the replacement filters just in case).

Thanks!

ryeguyy84
09/03/2013, 09:53 AM
membranes are usually good for a few years and if your TDS going in is really 22 then you should be good for a while. My incoming TDS is around 450 and i've had my membrane for 3 years now. i'm going to swap it out with my next filter change just for good measure but the output (pre-DI) is I think 7PPM if I remember correctly.

Keep up on your pre membrane filters to extend the life of your membrane.

Buckeye Hydro
09/03/2013, 02:18 PM
A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove much of the chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons. Remember that all the water you process, both waste water and purified water, go through the carbon block.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1,000 ppm. Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block (collectively called “prefilters” because the treat the water before it reaches the membrane) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 98%). The lifespan of a RO membrane is dependent upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the TDS in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

Russ

ryeguyy84
09/03/2013, 03:13 PM
I did not know you were supposed to lube the orings. . . so far no leaks but i'll keep that in mind.

Buckeye Hydro
09/03/2013, 04:09 PM
If you've ever heard someone complain that they can't get their housings unscrewed... they probably tightened the housing with a wrench, and never lubed the orings. People forget that the seal on these housings DOES NOT happen on the housing threads (like it does on pipe threads), rather it's the compression of that little oring that forms the seal.

They other thing we see is that sometimes people lube the orings, but they use a petroleum jelly (like Vaseline). That's to be avoided as it degrades the oring.

Russ

georgec
09/03/2013, 06:02 PM
Thanks for the info.

TDS for my area is low and my reading of 22 from the tap is consistent with others around here.

I'm using a hand TDS meter and not inline. So I'll have to pull some preDI to check. But it was 0 even before I replace my DI last week.

I have a 29G with sump and even with top-offs and 10-20% water changes weekly, I'm only making 10-15 gallons a week. Probably not more than 600 gallons per year. Do the prefilters (carbon in particular) lose their efficacy with time?

ryeguyy84
09/04/2013, 07:46 AM
If you've ever heard someone complain that they can't get their housings unscrewed... they probably tightened the housing with a wrench, and never lubed the orings. People forget that the seal on these housings DOES NOT happen on the housing threads (like it does on pipe threads), rather it's the compression of that little oring that forms the seal.

They other thing we see is that sometimes people lube the orings, but they use a petroleum jelly (like Vaseline). That's to be avoided as it degrades the oring.

Russ

Mind Blown. . . every time I change my filters I say how are people getting these things off?

Buckeye Hydro
09/04/2013, 09:22 AM
Well there you go!

When you tighten the housing (after lubing the oring of course) do it by hand, and only if necessary maybe just a little tweak (~1/8 of a turn) with the wrench. If it still leaks, then it is time to replace the oring. If you just crank on it with the wrench, you have to remember you can muscle your way right through the clear plastic housing. Bad thing is that the housing will probably break later when you're not standing there.

Here's a pic sent to us by someone who bought a used (unknown vendor) system and got a surprise one day

http://i224.photobucket.com/albums/dd293/BuckeyeFS/housingbrokeatthreads_zpsd54a5e8d.jpg (http://s224.photobucket.com/user/BuckeyeFS/media/housingbrokeatthreads_zpsd54a5e8d.jpg.html)

ryeguyy84
09/06/2013, 11:20 AM
A surprise like that would have my wife end my aquarium. When I left the water on one day and flooded my basement (RODI unit in on the first floor) she flipped.

basser1
09/12/2013, 08:12 PM
What do you suggest to use as a lube?

jkcoon
09/13/2013, 10:52 AM
What do you suggest to use as a lube?

I use silicone plumbers lube, found in the faucet repair section of your local home center comes in a small plastic flip-top container

Buckeye Hydro
09/23/2013, 04:19 AM
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