When to change Rodi cartridges

[Noldi76]

Hi guys,

i have a 4 Stage rodi. Carbon, sediment, membrane and resin. Tap Water is 128 tds. Post carbon/sediment around 118. Post membrane is 1 tds and post resin is 0 tds. What number is a good indicator when I should change certain cartridges in your opinion? The manufacturer recommends a particular time frame for each cartridge, but I think it would be wasteful to just switch out the cartridge when it turns out that it’s still perfectly fine.

 

[Spare time]

For the sediment, change it when the pressure drops (you need an inline pressure gauge for this but they are cheap)

For the carbon, you can use chlorine strips on the water water to see if chlorine is getting through. However, since most people don't test that regularly (understandably), many just replace it early when they replace the sediment cartridge.

For the RO membrane, change it when the TDS starts to go up into the DI resin. Be sure to flush, preferably before you start to collect water to use

For DI resin, change just before the color indication says it is completely used up. If it is not color changing, change as soon as TDS increases. Make sure to use a bypass for flushing to avoid burning through DI resin like paper on fire.

 

[ZoWhat]

When your handheld TDS meter goes to 2ppm

 

[Noldi76]

For the sediment, change it when the pressure drops (you need an inline pressure gauge for this but they are cheap)

For the carbon, you can use chlorine strips on the water water to see if chlorine is getting through. However, since most people don't test that regularly (understandably), many just replace it early when they replace the sediment cartridge.

For the RO membrane, change it when the TDS starts to go up into the DI resin. Be sure to flush, preferably before you start to collect water to use

For DI resin, change just before the color indication says it is completely used up. If it is not color changing, change as soon as TDS increases. Make sure to use a bypass for flushing to avoid burning through DI resin like paper on fire.

Thanks for the quick response. I have pressure meter before the unit already to adjust pressure going into the unit (60psi recommended). So based on your recommendation, I'd need a second one after the sediment filter to be able to register the change in pressure. Do you agree?
Also, I have been flushing the system prior to use. But how long do you actually flush for? I would assume as long as it takes for tds to drop until it stabilizes . Or am I wrong?

 

[Spare time]

Thanks for the quick response. I have pressure meter before the unit already to adjust pressure going into the unit (60psi recommended). So based on your recommendation, I'd need a second one after the sediment filter to be able to register the change in pressure. Do you agree?
Also, I have been flushing the system prior to use. But how long do you actually flush for? I would assume as long as it takes for tds to drop until it stabilizes . Or am I wrong?

You want to have the pressure gauge after the sediment and carbon and before the RO membrane. You can move your current one to that spot.

As for flushing, a minute is usually enough, but its really just whenever the TDS going into the DI resin / DI bypass stops dropping (it will rise dramatically and then fall down).

 

[Uncle99]

Replace when post membrane is 5ppm, or you start too really chew up the resin, which, as you know, is very expensive.

 

[Noldi76]

You want to have the pressure gauge after the sediment and carbon and before the RO membrane. You can move your current one to that spot.

As for flushing, a minute is usually enough, but its really just whenever the TDS going into the DI resin / DI bypass stops dropping (it will rise dramatically and then fall down).

But how do you tell if the pressure is dropping in the sediment filter if you only have one pressure gauge? You have nothing to compare it to. Keep in mind I am manually adjusting the valve going to the RO unit to 60PSI. So if the pressure is higher or lower in the building, i'd be adjusting the valve accordingly. That's not a constant. What do you k ow that I don't?

 

[mdb_talon]

Change prefilters(carbon/sediment) frequently) is the cost effective way. They are cheap and can significantly increase life of more expensive RO. A decent RO should last at least a couple years for average hobbyist. DI i change based off color(though occassionally i test TDS just to confirm it is good.

 

[Spare time]

But how do you tell if the pressure is dropping in the sediment filter if you only have one pressure gauge? You have nothing to compare it to. Keep in mind I am manually adjusting the valve going to the RO unit to 60PSI. So if the pressure is higher or lower in the building, i'd be adjusting the valve accordingly. That's not a constant. What do you k ow that I don't?

Having one before the sediment is only useful if your buidling's water pressure fluctuates. If it does then go ahead and do that.

This is the video I reference for pressure gauges