Ro/di
- Thread starter rlopez537
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I change my every 6 mths just to insure I continuously get good water quality. It will depend on your actual usuage too. I do a 5g water change every week plus make about 15g per week for auto top off container plus another couple of gallons for drinking.
The sediment filter and carbon block should be changed every 6 months. The RO membrane should last 3+ years if you keep up with the replacements using high quality filters and do an annual disinfection. I have seen membranes go 10 years and my personal system is over 6 years now and still over 99% rejection rate.
The DI resin or cartridge should be changed when the TDS is anything other than 0 on a consistent basis.
You can extend the sediment and carbon replacements if you install pressure gauges on the incoming tap water line and after the carbon block so you can monitor filter plugging or headloss and you also buy and use a low range chlorine test kit to monitor for chlorine breakthru past the carbon which would toast a RO membrane. Most find it easiest to just mark 6 months on the calendar and stick with that.
The DI resin or cartridge should be changed when the TDS is anything other than 0 on a consistent basis.
You can extend the sediment and carbon replacements if you install pressure gauges on the incoming tap water line and after the carbon block so you can monitor filter plugging or headloss and you also buy and use a low range chlorine test kit to monitor for chlorine breakthru past the carbon which would toast a RO membrane. Most find it easiest to just mark 6 months on the calendar and stick with that.
Unfortunately that is not true.
Sediment filters and carbon blocks only remove TSS or suspended particles, large stuff, and a clittle chlorine and metals. The chlorine and metals may account for 1-2 ppm TDS so are very minimal and the suspended solids do not register on a TDS meter since they are not dissolved, TDS. Sediment and carbon filters are rated at things like 10 microns, 5, 1, or if they are really really good maybe 0.5 or 0.2 microns. On the flip side TDS or dissolved solids, the things that register on a TDS meter are in the 0.0001 micron range, thousands of times smaller than suspended solids.
For the most part on the RO membrane and the DI resin remove TDS so a TDS meter tells you nothing about sediment and carbon block filter condition. For this reason it is recommended you change your sediment and carbon every 6 months like clockwork since their sole purpose is to protect the RO membrane so it can do its job of removing 90-98% of the TDS which in turn protects the DI filter which removes the remaining 2-10%.
Another indication of sediment and carbon condition is by using an inline pressure gauge to monitor headloss of filter plugging or fouling. When you start to see a significant loss of pressure between the system sitting idle or static pressure and when it is operating or flowing pressure the filters are in need of replacement. To take it one step further you can purchase a low range chlorine test kit and monitor after the carbon for chlorine breakthru. Good carbon should remove all the chlorine while plugged or fouled carbon will allow it through. Carbon is made up of billions of tiny microscopic pores so it is critical to use a high quality, low micron, absolute or near absolute sediment filter to protect that carbon so it can do its job. I recommend no larger than 1 microns for both the sediment and carbon and 0.5 or 0.6 is even better. Personally I use a 0.2 micron absolute rated sediment filter and a 0.5 micron single carbon block and I have two pressure gauges, one before the sediment filter and one after the carbon so I can see pressure drop at a glance and have and use a clow range chlorine test kit. I get about 18 months out of a filter set in this way but if I did not monitor I would stick with the industry standard 6 month intervals and disinfect the system at each filter change.
As an FYI, you can see 40 microns with the unaided human eye so a 5 or 10 micron sediment filter is really about as effective as a screen door for protceting the carbons pores in my opnion. Good filters don't cost that much more and will extend the life of your RO membrane and DI so really pay for themselves.
A TDS meter tells you the condition of your RO membrane and your DI resin, the two pieces that remove TDS. You really should be taking three TDS readings on a regular basis, tap water TDS or better yet softened tap water TDS if you have a softener, RO only TDS beflore the DI and the final RO/DI. You need all three, not just the final RO/DI since it is the RO that does 90-98% of the treatment. You use the tap and RO TDS readings to determine the rejection rate or removal efficiency of the RO membrane and the final RO/DI to determine when to change the DI. If the rejection rate is not in the 97-99% range then a new membrane might be awise investment since every 2% you lose in rejection rate, ie 98% down to 96%, cuts your DI life in half so you are replacing exppensive resin twice as often.
Sediment filters and carbon blocks only remove TSS or suspended particles, large stuff, and a clittle chlorine and metals. The chlorine and metals may account for 1-2 ppm TDS so are very minimal and the suspended solids do not register on a TDS meter since they are not dissolved, TDS. Sediment and carbon filters are rated at things like 10 microns, 5, 1, or if they are really really good maybe 0.5 or 0.2 microns. On the flip side TDS or dissolved solids, the things that register on a TDS meter are in the 0.0001 micron range, thousands of times smaller than suspended solids.
For the most part on the RO membrane and the DI resin remove TDS so a TDS meter tells you nothing about sediment and carbon block filter condition. For this reason it is recommended you change your sediment and carbon every 6 months like clockwork since their sole purpose is to protect the RO membrane so it can do its job of removing 90-98% of the TDS which in turn protects the DI filter which removes the remaining 2-10%.
Another indication of sediment and carbon condition is by using an inline pressure gauge to monitor headloss of filter plugging or fouling. When you start to see a significant loss of pressure between the system sitting idle or static pressure and when it is operating or flowing pressure the filters are in need of replacement. To take it one step further you can purchase a low range chlorine test kit and monitor after the carbon for chlorine breakthru. Good carbon should remove all the chlorine while plugged or fouled carbon will allow it through. Carbon is made up of billions of tiny microscopic pores so it is critical to use a high quality, low micron, absolute or near absolute sediment filter to protect that carbon so it can do its job. I recommend no larger than 1 microns for both the sediment and carbon and 0.5 or 0.6 is even better. Personally I use a 0.2 micron absolute rated sediment filter and a 0.5 micron single carbon block and I have two pressure gauges, one before the sediment filter and one after the carbon so I can see pressure drop at a glance and have and use a clow range chlorine test kit. I get about 18 months out of a filter set in this way but if I did not monitor I would stick with the industry standard 6 month intervals and disinfect the system at each filter change.
As an FYI, you can see 40 microns with the unaided human eye so a 5 or 10 micron sediment filter is really about as effective as a screen door for protceting the carbons pores in my opnion. Good filters don't cost that much more and will extend the life of your RO membrane and DI so really pay for themselves.
A TDS meter tells you the condition of your RO membrane and your DI resin, the two pieces that remove TDS. You really should be taking three TDS readings on a regular basis, tap water TDS or better yet softened tap water TDS if you have a softener, RO only TDS beflore the DI and the final RO/DI. You need all three, not just the final RO/DI since it is the RO that does 90-98% of the treatment. You use the tap and RO TDS readings to determine the rejection rate or removal efficiency of the RO membrane and the final RO/DI to determine when to change the DI. If the rejection rate is not in the 97-99% range then a new membrane might be awise investment since every 2% you lose in rejection rate, ie 98% down to 96%, cuts your DI life in half so you are replacing exppensive resin twice as often.
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