General RODI Filter Replacement Discussion

[Airwolf]

Since my RODI unit has been in operation for almost a year and half now, I had some general questions regarding filters and their replacement.

General Usage: About 4 gallons of RODI water (aquarium water) and 4 gallons of RO water a week (coffee pot, hot water pot for teas). So all in about 400 gallons a year.

General TDS: Pre resin fluctuates between 1-2 and settles in at 1 as the unit runs, post resin is zero. Resin is showing about 1/2 used.

General operation: Using the flush valve flush for about 2 mins before collecting any water. I then fill the RO water containers (1-2 gallons) to help the TDS settle to the lowest setting, then if more aquarium water is needed I will fill those containers. Finally if aquarium water is made I will fill the last RO water container and when it is near full, will flush the system again for a couple minutes. I generally 'make water' once a week.

Onto the Questions:

1) My sediment filter, looks like the day I first put it in service. Nice and white with little to no visible debris on it. I also have not noticed any significant pressure drop, other than the fluctuating pressure from my city. A whole different discussion for a different time. My question is, since the sediment filters looks new and there has been not noticeable drop in pressure, should one replace at a regular interval or just when dirty/pressure drop?

2) Carbon blocks, currently have two with the low usage, is there any need to replace them? Most reading online says 6 months replacement interval.

3) Micron filtration level: looking online I see .5/1/5 micron sediment and carbon filters. What is the general thought here. Does going to .5 really provide that much better per membrane filtration versus a 1 or 5? I understand the answer to the question is 'yes' as .5 is sized particle it can catch, but is there any appreciable difference to membrane life with the different micron sediment/carbon filters?

Looking forward to a lively discussion!

 

[EricR]

1-2 TDS post-RO is pretty awesome to me. Your source water must be way cleaner than mine.

Personally, with what you posted, I wouldn't change either (sediment or carbon) yet.
I just go with:
-- Sediment when it starts to look dirty
-- Carbon; I check chlorine level in waste water and change when I see any,,, but also monitor pressure to RO membrane as you mentioned

Good luck. I'm sure you'll get better responses from others with more experience than I have...

 

[KStatefan]

I have a whole house filter so my sediment does not see any of the big stuff. I will change it when the pressure drop across it increases. It is two years old now.
Carbon filters I go by amount of water and the rating of the filter. I am changing the first carbon at 2,000 gallons rated at 6,000 and the second one at 8,000 rated at 20,000.

I use a 0.2 micron absolute rated sediment filter. My first carbon is 5 micron and the second is 0.5 micron.

 

[Woodyman]

Since my RODI unit has been in operation for almost a year and half now, I had some general questions regarding filters and their replacement.

General Usage: About 4 gallons of RODI water (aquarium water) and 4 gallons of RO water a week (coffee pot, hot water pot for teas). So all in about 400 gallons a year.

General TDS: Pre resin fluctuates between 1-2 and settles in at 1 as the unit runs, post resin is zero. Resin is showing about 1/2 used.

General operation: Using the flush valve flush for about 2 mins before collecting any water. I then fill the RO water containers (1-2 gallons) to help the TDS settle to the lowest setting, then if more aquarium water is needed I will fill those containers. Finally if aquarium water is made I will fill the last RO water container and when it is near full, will flush the system again for a couple minutes. I generally 'make water' once a week.

Onto the Questions:

1) My sediment filter, looks like the day I first put it in service. Nice and white with little to no visible debris on it. I also have not noticed any significant pressure drop, other than the fluctuating pressure from my city. A whole different discussion for a different time. My question is, since the sediment filters looks new and there has been not noticeable drop in pressure, should one replace at a regular interval or just when dirty/pressure drop?

Either would work, but if your not seeing a drop the filter still has usable life. Some recommend replacing yearly just as a precaution for any bacterial buildup.

2) Carbon blocks, currently have two with the low usage, is there any need to replace them? Most reading online says 6 months replacement interval.

Grab a cheap chlorine test kit, or if you want more precision and don't mind the expense Hanna makes a meter as well. That's the best way, chlorine can vary widely from one person to another because of each municipalities use of chlorine and/or chloramines. However at 400g of use your fine, you shouldn't be seeing any significant chlorine breakthrough at that level of consumption. What carbon blocks do you have installed? It may be rated for 2000g +/- (levels of chlorine/chloramines affect that rating as well).

3) Micron filtration level: looking online I see .5/1/5 micron sediment and carbon filters. What is the general thought here. Does going to .5 really provide that much better per membrane filtration versus a 1 or 5? I understand the answer to the question is 'yes' as .5 is sized particle it can catch, but is there any appreciable difference to membrane life with the different micron sediment/carbon filters?

Yes, I'm currently building data for our hobby, but I have years of real world experience using larger size RO systems and it does prolong the useful life of the membrane. The sweet spot between cost and extended life if another debate, but ignoring that factor extended life should be prioritized in theory.

 

[Buckeye Hydro]

I have a whole house filter so my sediment does not see any of the big stuff. I will change it when the pressure drop across it increases. It is two years old now.
Carbon filters I go by amount of water and the rating of the filter. I am changing the first carbon at 2,000 gallons rated at 6,000 and the second one at 8,000 rated at 20,000.

I use a 0.2 micron absolute rated sediment filter. My first carbon is 5 micron and the second is 0.5 micron.

Think about putting your highest CAPACITY carbon before the lower capacity carbon