When to change RO/DI filters?

[JCR's Reef]

Well I figured its about time for me to change out my filters considering its been almost a year since I have bought my RO/DI system and still have never changed anything. Its a six stage 100gpd unit that also produces drinking water. Granted my first 3 stages of RO are used alot more then the others as we use it everyday. Right now my inline TDS meter says I'm at 2, but thats after I have been running it for awhile. When RO/DI is first turned on it will go up to 8 then slowly start to come back down but takes about 30 min. for it to reach 2.
My incoming water is acutally pretty clean @ 183 vs. most people are @ 300 and up.

I'm getting ready to buy some filters, so my question's are:

How do you know when to change out the membrane?
I have no idea what the membrane even does. I've read it should be changed out every few years, some can last as long as 5 yrs, but how do you know?

When to change out the DI resin?
I use the color changing beads but wonder if I should really rely of them to fully change color or not.

Has anybody ever re-charged their DI resin? Thought about it but wonder if its worth the hassle.

How often are you guys changing out your carbon/sediment filters?
If I go with a 1 micron sediment filter, will I be changing this out monthly vs. a 5 micron one?
What are you thoughts about chlorine, etc.. breaking down the carbon filters? Does it have to be a certain filter to strip these out? How often should they be changed? I have never noticed any ill effects, nor do I use anything to remove it from my top off/ make up water.

Also, are you using some type of buffer to replace the good chemicals that are stripped away? I havent been but wonder if it would actually benefit me to start.

Just would like to get an idea if you are strictly relying on your TDS, or if you change out other filters following some type of routine?

 

[mojo~]

I change the prefilters about every 8 months or so. THe membrane shouldnt need to be replace but every couple years. depends on your tds some.But the more clogged it gets the less efficient it is. Thats why some of the new ones come with a back flush booster pump. Keeps the Membranes clean fora very long time. The Di I change when my tds goes up. It is still 0 and its been in 6 months. when it comes up to 1 I ll order a new DI cartridge from BRS and change it out. thats still pretty good.

 

[LornaS]

Do any of you use the bulk di resin? I bought 5 lbs of it from bulk reef supply and change it in a refillable cartridge every 6-8 months. Then again I am on a well and the water is disgusting so I tend to change the prefilters about every 3 months or so and the di about 8 months depending on the tds reading. I back flush the membrane every time also. My filter array I have set at 10, 5, 1 micron. I find that is the most efficient as the first blocks the big stuff and then gradually reduces. If your first is a 1 then it clogs really fast and the other 2 don't have much work....

 

[JCR's Reef]

I dont think I have a back flush kit on my unit.
I'm going to be ordering one of the resin packets and was thinking about ordering a canister to hang on the wall for the DI but I dont think I really need it.
So there is no reason to buy the chlorine filter to run in the unit? Most probably arent running it in their filter system so there is probably no need too.

 

[LOVETHISHOBBY]

I change my filters every two months. The pre-filter and even the first carbon filter get pretty bad from all the crap in the water. It makes sick thinking that I'm drinking it. I change my DI resin about every 6 months. I use the color changing kind, but change it long before the color changes. I refill by own cartridges. It's easy and alot cheaper. If you do regular water changes, the buffers in the salt replace what's being stripped out by the filter.

 

[JCR's Reef]

I knew there was a stickler in the club somewhere that had a routine LOL. I thought I was being a little too paranoid for wanting to change things out before I relied on the TDS meter. Mainly concerned w/ the clogging issue which I think I'm going to go with every 3 months changing them out and the DI every 9 months. I probably dont change as much water as you guys do. I find the less I do, the better it is. Still haven't figured out if thats a good thing or a bad thing yet?
The main reason I asked these questions is that before I was doing weekly water changes and noticed a little bit of algae and the glass and stuff. Once I went with monthly water changes it subsided quiet a bit so I figured my TDS was off or something is a miss. I'll just go ahead and change them out then.Thanks for the input guys and gal...

 

[SeasonedReefer]

I usually go off my Tds reading once I hit double digits I order new filters. That or if my sediment filter looks really rusty ill change it. I guess it depends on your water quality to start with.

 

[Buckeye Hydro]

This may help:

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the useable 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. The Matrikx+1 (“Chlorine Guzzler”) for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.

Regarding your RO membrane and DI resin, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in three places:
1. Tap water
2. After the RO but before the DI
3. After the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (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 filter (collectively called “prefilters”) 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 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 less purified water (aka “permeate”), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependant 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 total dissolved solids (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 less water as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm to 3 ppm, 5 ppm, and higher, 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!

Russ

 

[JCR's Reef]

Thanks for posting Russ. That cleared up most, if not all of my ?'s. Thanks

 

[xzoemar]

I ran an experiment today that may be of interest. I have a 15 gallon pressure tank. Even though our family uses a lot of RO, the water can sit in there for a while before use. I checked the TDS at the kitchen sink... about 80. I checked TDS at the aquarium auto top off... about 70. I started to purge the pressure tank. After I had purged about 5 gallons, the TDS was at about 60. I purged most of the water from the system and then let it start to regenerate. A couple of hours later, I filled a 5 gallon bucket. My TDS measurements during the fill ranged from 7 to 11. About an hour later, I filled a second bucket and the TDS readings ranged from 2 to 5. This shows us that the corrosive nature of the RO water results in TDS creep as it sits in the storage tank. My storage tank and RO system as a whole was new in January. Thanks to Chad for letting me borrow his TDS meter. Brian

 

[JCR's Reef]

I only have a 3 gallon tank and I empty it completely every couple of weeks. Just something about water that still becomes stagnant in my book.

 

[Buckeye Hydro]

Rather than the corrosive nature of the RO water, the primary cause of what you are seeing is pressure. We don't recommend use of pressurized storage tanks for most systems used in this hobby for this reason.

Can a system be configured to supply RO water to a pressure tank, and RO water (not from the tank) to the DI stage? Sure. Being careful not to make a "commercial post" here, let's just say we are very familiar with such a system.

If you want to see systems configured incorrectly in this regard, there are examples galore available on ebay...

Russ