RO/DI questions

[Dee]

I'm full of them tonight. Mostly because my husband gets too frustrated looking online and finding no information.

Okay...we have a Coralife Pureflow 100gl/day RO unit with add on DI. We have clogged filters and are trying to find information on how many gallons each filter section can handle...so we know which filters are most likely clogged because we can't afford all of them right now.

Any help, direction, anything ???

Dee

[topsoil]

I'm not familiar with the coralife RO unit. I bought a watts premier RO unit from costco (i'm cheap, what can I say) and added on a DI unit. From what I remember when I changed mine out, it wasn't the pre-filters that limited the water flow so much as it was the RO membrane unit. I bought my replacement filters through the watts on-line website, and the replacement pre-filters were all the same, with the only difference being the membrane filter section. The higher flow membrane units were obviously more expensive. they were sold as kits, so I got 2 pre-filters and a membrane unit (for a 3-stage system). If your membrane isn't that old, maybe you just need a pre-filter? I think most pre-filters can handle a pretty high flow rate. I think it's the membrane that's the limiting factor on the flow rate. hope that helps.

[Bill S]

Dee,

Contact Russ at www.buckeyfieldsupply.com (http://www.buckeyfieldsupply.com). Even though you don't own one of his units, he'll be glad to help you out.

BTW, I have that same Coralife unit sitting on the floor of my garage. I'm pretty sure it will just go in the trash - the unit is such junk, IMO, that I can't let someone else go down the road with it. I'd seriously consider doing what I did - replace the entire unit with one from Buckeye.

[Dee]

He ended up ordering the pre-filters. Unfortunately we can't replace the unit. We can't afford to right now and this one is only about 4mths old. We're stuck with it for a while.

Dee

[BuckeyeHydro]

I'm full of them tonight. Mostly because my husband gets too frustrated looking online and finding no information.

Okay...we have a Coralife Pureflow 100gl/day RO unit with add on DI. We have clogged filters and are trying to find information on how many gallons each filter section can handle...so we know which filters are most likely clogged because we can't afford all of them right now.

Any help, direction, anything ???

Dee

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 its 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 then would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal!

Have your husband give us a call if he'd like.

Russ @ BFS
513-312-2343

[Dee]

Okay, I'm printing this out and studying it so I can figure this out on my own. This sort of stuff has me out in left field...huh...what? LOL. My husband is impatient about finding a "fix" for things so I guess I need to actually understand the process so I can just tell him what to do...will make life much easier. Thanks for this awesome post!!!!

Dee

[CoryDude]

Leave it to Russ. Man, that guy's an encyclopedia of info.

Here's the simplest way to see if the RO unit is filtering correctly. Order a TDS meter. They run from $15-$40 depending on the type/brand. A TDS meter just measure any impurities in the h2o.

Then get a chlorine test kit from your lfs or pool supply store. If you're getting a reading of 0-10 on the TDS and there's no chlorine detected, then your RO filter is working great.

Good rule of thumb is to replace pre-filters every 3-4 months and your RO filter (the expensive one) every few years.

Buckeye really is a good company and they have the cheapest prices on filters, that I've seen. Plus, they have a very helpful FAQ section that covers a lot of diff. topics.