Water purifier filter change frequency?

[LeslieS]

Hi Everyone,

I have a Pure-Flo II by Coralife Water filter. The instructions said to change the filters every 3000 gallons. After 95 gallons, the first stage (the one that I can see) was brown. I changed it just to be on the safe side. What does everyone else suggest?

Thanks,
Leslie

 

[masterswimmer]

Get a TDS (Total Dissolved Solids) meter. Check your processed water. If the water reads zero TDS (desired level) then your filter is still working properly.

swimmer

 

[DevIouS]

It should still work efficiently, as it's fairly new......unless your local water is that bad.
The first stage will be the first & fastest to turn brown. It is also the one that has the shorter life span & needs to be changed more often.


Like Russ stated, the best way to know if your filters need changing, is to test your newly made water.
I find the "in-line" TDS meter to be great. It will test your incoming & outgoing water with the press of a button.

 

[tomzpc]

Do you have a DI canister on that unit? That is the one that you'll need to change depending upon if you have color changing resin or based on TDS reading. The pre-filter that turns brown is just a sediment filter. If your production has slowed then it is time to change it. I usually change the second pre-filter(the carbon block) at the same time. If you change both and production is still slow then most likely it is time for a new RO membrane which is the costly part of the system. I usually get a couple of years out of mine.

 

[joseney21]

get a dual inline tds meter

 

[Buckeye Field Supply]

This should 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 filers is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. The Matrikx+1 (?Chlorine Guzzler?) for example will remove >90% 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 ppm. Common readings are 100 to 400. So for sake of discussion, let's say your tap water reads 400. 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 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 meter like this: http://www.buckeyefieldsupply.com/showproducts.asp?Category=42&Sub=1
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. Usually 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.

 

[LeslieS]

Great explanation! Thanks