What kind of maintenane should I be performing on my RO/DI unit?

[LennyD4]

I have a SpectraPure RO/DI unit and I am wondering how often I should change the filters. I also would like to know if there is any other kind of maintenance I should be performing on this unit. If so, how often should I be doing these ?

[kriv4o]

I have the 90 gpd Spectra Pure refurb unit and just changed all my filters. I noticed that the TDS at the output of th unit was different than the usual 0 and I saw an algae grew faster the last couple of weeks so I figured it was time for new filters.
That'sall the maintenance I've done to mine.

[Steve175]

Agree with above: by a TDS meter (Spectrapure sells them as well as BRS) and change the filter/carbon/DI then. I change the RO membrane less often (12-18 months vs. 4 months for others [but I make ~ 200 gallons of water per week, filter changes may be less for you]

[Spyderturbo007]

I have the same unit and did purchase a TDS meter. So I just run the unit until the TDS meter doesn't read 0 anymore?

I have also seen some units that sell a specific chloramine removal stage. My municipality uses chloramine so do I need to purchase one of them or will my RO/DI unit handle the chloramine removal?

[Palting]

The filters expire at different times. The exact times depend on the TDS of the tap water, the frequency of use, etc. The prefilters and the carbon filters usually need to be changed at about 3 months, the membarne maybe about 1-2 years, an the DI filter can last about 3-6 months as well.

There are several things you can do to make sure you change the filters at the right time. Not too soon and waste money, and not too late and have dirty water.

Put a pressure gauge between your pre-filters and your membrane. As the prefilters and carbon get clogged up and used up, the pressure willl drop and get low. That's wjhen you change the prefilters.

You should have a flush kit for the RO membrane. Flush the membrane for about 30 seconds before and after use. This will prolong the life of the membrane.

Place a TDS meter after the membrane and another one after the DI resin. Alternately, you can use one TDS meter and check those spots intermitently, but that's a pain. Anyhow, when the TDS afte the resin starts to rise, it's time to change the resin. When the TDS after the membrane starts to rise, then it's time to change the membrane.

The pressure gauge and the twin TDS meters will pay for themselves over time by letting you keep the same filters until the time is right to replace them. Here's my experience as an example. The TDS of my tapwater is about 130. I use about 40 gallons RODI each week. My prefilters lasted almost 18 months before the pressures started to drop and I had to change them. My RO membrane is now over 2 years old, and the TDS after the membrane is still at 2. Since the TDS after the membrane is so low, my DI resin is also lasting a long time. It was almost 2 years before the final output TDS went up from zero to 1, so I had to replace the DI resin.

A for chloramine, you have to get chloramine specific units. The regular units cannot handle chloramine.

[kriv4o]

It's a great advantage knowing of the bat what' s in your tap water. If I were you I'd call the tech support of Spectra Pure, give them as much info as you have on your tap water, let them know what are you using it for and let them recommend a filter combo......

[Spyderturbo007]

A for chloramine, you have to get chloramine specific units. The regular units cannot handle chloramine.

EDIT -> I found this after almost having a heart attack thinking that my unit wouldn't remove the chloramine. Are you correct, or is this article (http://reefkeeping.com/issues/2003-11/rhf/feature/index.php) correct?

[Buckeye Hydro]

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 99% 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 1000 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 life span 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

[Buckeye Hydro]

Regarding chloramines - you may be ok with one carbon stage - but we add a second carbon stage to treat chloramines. It is a very inexpensive bit of insurance.

Russ

[reefbat]

I replace the different filters at different intervals or when I notice the pressure dropping from what it normally is. I try to replace the sediment filter every 6 months, the carbon blocks every year, and the membrane is now due for a replacement at 3yrs. 0tds in/out according to my meter but my city water is pretty clean to begin with. Don't forget to back flush the unit every so often as well if it's so equipped to help keep the membrane clean. I haven't replaced the DI resin and i'm not really sure that I even need to unless the tds starts creeping up.

[Buckeye Hydro]

Don't forget to back flush the unit every so often as well if it's so equipped to help keep the membrane clean.

I'm on a one-man crusade to get people to stop referring to this as "BACK flushing." There's no reversal of flow involved.

For some reason people started calling it "back flushing" and it confuses the new guys!

Russ

[reefbat]

What would be the correct term? I think the piece on my BRS unit is just called a flush kit.

[Palting]

EDIT -> I found this after almost having a heart attack thinking that my unit wouldn't remove the chloramine. Are you correct, or is this article (http://reefkeeping.com/issues/2003-11/rhf/feature/index.php) correct?

Sorry if I almost caused you to have a heart attack. I certainly would not contradict anything that Dr. Holmes-Farly says. I bow to anything he says in chemistry or even aquarium related matters.

However, consider this. There are units designed to handle chlorine treated water, and there are units that are designed to specifically handle chloramine treated water. If I knew my water was chloramine treated, I would get the unit specifically designed for chloramine, not just chlorine. Your choice.

[Buckeye Hydro]

What would be the correct term? I think the piece on my BRS unit is just called a flush kit.

"Flush"

[Spyderturbo007]

Sorry if I almost caused you to have a heart attack. I certainly would not contradict anything that Dr. Holmes-Farly says. I bow to anything he says in chemistry or even aquarium related matters.


No worries, but I think my heart did skip a beat. :D

After spending a wheel borrow full of money and countless hours getting things set up and finishing the cycle I read your post. I'm sure you could imagine my horror when I thought all my time and investment was ruined.


However, consider this. There are units designed to handle chlorine treated water, and there are units that are designed to specifically handle chloramine treated water. If I knew my water was chloramine treated, I would get the unit specifically designed for chloramine, not just chlorine. Your choice.

I'll have to look around and see what they cost. I always hate buying something twice.

Don't forget to back flush the unit every so often as well if it's so equipped to help keep the membrane clean.

I didn't see anything about that in my user manual? I'm guessing my unit isn't equipped for that procedure?

[Buckeye Hydro]

No need to buy a new unit. You can get an add on housing kit and be done with it for under $30.

[Spyderturbo007]

Do have any suggestions? I didn't see one on your website.

[Buckeye Hydro]

I sent you some specific information.

What are the spec's on the prefilters you are using now?

Russ