ro/di system

[purplesprite]

Need some help here.When is it time to change the filters on the ro/di.My TDS meter is reading 217 going in and 57 coming out.Thats pretty bad huh?I dont know i thought it should be zero coming out, atleast it used to be.Oh yea and what filters do i change all of them?

[Enigma13]

Now is the time. You probably want to change when the TDS readings get above 10 coming out.
As to which filters you change- How old is your unit? If it is fairly new you might have just exhausted your di resin and that will be all you need to change. If more than six months since your changed filters I would probably change the pre-filter and carbon block filter too. If over a year it is probably time to change the membrane as well (though you might want to try changing the others and see where you get before taking this step, as it is more costly than all of the others put together).

[Bill S]

What brand? Can you check your TDS going into the DI? If it's over 6 months, do the filters and resin. Treated correctly - and I know how to NOT treat them correctly - the membrane should last for years.

[seamonkey2]

rule of thumb, change all filters every 6 months, the membrane every 2 years.

also depends how much water you run thru them

Jose

[JimD]

I always change sediment, carbon and DI when the TDS is above 3ppm. It all depends on how much water you put through it and the condition of the source water. This way you get maximum life out of the RO membrane.

[Bill S]

And don't forget to regularly flush the membrane (monthly)

[BuckeyeHydro]

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 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 (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. How do you measure TDS? With a TDS meter like this: http://www.buckeyefieldsupply.com/showproducts.asp?Sub=149&showspecials=149 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.

[purplesprite]

Thanks very much for all the helpful information.