tds meter?

[sharkboy]

does anyone have one of these so that I can check if my ro/di unit is still functioning properly? How often do membranes have to be replaced? I have been running mine for about 9 months. Any suggestions/recommendations?

[ou812pezz]

I have a meter at 1604 and braun if you want to bring a sample by. Changing filters depends on use and type of water.

[Bill S]

Membranes should last for years... If they haven't been destroyed by too much pressure.

[sharkboy]

How about the filters inside the canisters...do these get replaced or rinsed or what?

[OldSalty]

Change them at least every 6 months, if chlorine gets to the membraine it will destroy it. get a chlorine test kit, like from a swiming pool place. Take a sample of your water. If ya see chlorine the filters are bad.
Change tmem ASAP

[jrhein]

What are you looking to get your TDS at? Is 9 ok?

[Instar]

TDS of 9 is great! You start out approx. somewhere between 350 and 485 depending on aquifer, tower, etc.

[BuckeyeHydro]

How about the filters inside the canisters...do these get replaced or rinsed or what?

This may help:

When should I replace my filters?

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/sh...owspecials=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. 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.