RO/DI Assistance Needed

[MatAndPatti]

We're going to finally headwally be setting up our 40G breeder, so our water needs will be high enough to not want to lug the water from the LFS anymore (as we've been doing for our current 8g). I've done a bunch of reading up on RODI systems here but I still have a few questions...

Is it true that if the system is turned off for a some time, that the first bit of output water (the next time it's turned on) will not be at 0 TDS and should be discarded? If so, how much water gets discarded, usually? Does the cycling on and off affect the lifespan of the filters at all? I can imagine that we will only have the system on for relatively short periods of time every week or so, or am I missing something here?

Also, does anyone in the Rochester area know if we need to worry about Chloramines here? We live in Henrietta and are on Monroe county water. I see BRS has a system that handles those as well, but I'm not sure it's necessary for us.

I'm thinking about picking up the BRS 75 gpd 5 Stage Plus system during the group buy next week (yes, I still need to register!). Is this system overkill for our needs? We're only going to need ~5-10 gallons per week. Anyone have alternative suggestions? Seems like 75 gpd is about the lowest flow rate for a system that's appropriate for aquarium use.

Thanks!
Mat

 

[Gary Majchrzak]

I'm no RO expert but I don't understand why a 25GPD unit wouldn't work just fine for you

 

[Paradiddle7]

The main thing you need to know about a RODI unit is NOT go on ebay and buy a cheap one. Or you can buy a cheap one on Ebay and throw away all the filters they give you (Except the RO membrane) and buy better filters from BRS or Spectrapure. Start with a good system and make sure you keep your DI resin canister vertical and NOT horizontal where water can channel where the DI beads are NOT packed in. The cheap units have a horrible DI chamber and they always mount them horizontally. The BRS unit allows you to pack the DI resin into an insert and is much easier to get it perfectly full so that no water can escape the DI beads.

You don't need to "throw away" the high TDS water but you can since you have a small system. The main things you need to know about "TDS creep" is that you should try to make your RODI in large batches. This way the TDS will equal out to very low if even registerable. This helps preserve the membrane as well and so does flushing it. If you have high TDS as soon as you turn on your RODI, you can turn it off and flush the membrane for 10-20 minutes and that will help. It's way better for the membrane and to keep tds low to make large batches, for you maybe 30-50 gallons at a time would work. That should last you a good two weeks to refill your auto top-off and also water changes. I have a 110g total system volume and I make about 50 gallons every 2 weeks.

 

[Paradiddle7]

Oh, and one more thing. No offense to Gary, but get yourself a 75 gpd RODI unit because your 8 gallon tank, has already turned into a 40g breeder and your next step will be a 90-120g tank and you won't have to buy a new RODI!!!!

 

[Buckeye Hydro]

Is it true that if the system is turned off for a some time, that the first bit of output water (the next time it's turned on) will not be at 0 TDS and should be discarded? If so, how much water gets discarded, usually? Does the cycling on and off affect the lifespan of the filters at all? I can imagine that we will only have the system on for relatively short periods of time every week or so, or am I missing something here?

There was a good response to this question above

Also, does anyone in the Rochester area know if we need to worry about Chloramines here? We live in Henrietta and are on Monroe county water. I see BRS has a system that handles those as well, but I'm not sure it's necessary for us.

Here's is your drinking water quality report: http://www.mcwa.com/watqual.htm

No signs of chloramine use and we wouldn't recommend more than a 4 stage system for you.

Seems like 75 gpd is about the lowest flow rate for a system that's appropriate for aquarium use.

With your tank size I'd go with a 75 gpd system or a 50 gpd system, but because they are about the same price, you might as well get the 75 gpd system, especially if you think you mihgt be getting a larger tank.

Plan on running your system at least once per week.

 

[Gary Majchrzak]

I'm thinking about picking up the BRS 75 gpd 5 Stage Plus system during the group buy next week (yes, I still need to register!). Is this system overkill for our needs? We're only going to need ~5-10 gallons per week. Anyone have alternative suggestions?

I don't sell 'em and I'm no expert on RO units
HOWEVER
I can tell you that I successfully used a 3 stage (carbon block, micron filter & tfc membrane RO) 25GPD RO unit to provide water for my 75 gallon and 225 gallon aquariums for over a decade.

Even at this point in time I do not have a 5 stage RO unit and I do a 50 gallon water change weekly PLUS produce 30 gallons of RO for kalkwasser (makeup water).

In order to produce 5-10 gallons a week for a 40 breeder (you'll probably end up needing a little more) I would think a 25-50GPD 3 or 4 stage RO unit more than enough.

One of the most important items (IMO) is an auto shutoff for your collection barrel

 

[iamwrasseman]

unless you have room to store the water i would use a smaller unit but if your going to have corals then i would suggest ro/di .a 29 gpd would be large enough but i also see where your going so you may want to get a 50 to 75 gpd unit as they seem to haave more bells and whistles too . $165 gets you a nice 75gpd ro/di unit with dual tds meter and an auto shutoff built in with a flush valve too !

 

[MatAndPatti]

The main thing you need to know about a RODI unit is NOT go on ebay and buy a cheap one.

For sure! Learned that one by reading enough of the forum posts here at RC. Definitely don't want to step in the same mess that others have dealt with.

The main things you need to know about "TDS creep" is that you should try to make your RODI in large batches. This way the TDS will equal out to very low if even registerable. This helps preserve the membrane as well and so does flushing it. If you have high TDS as soon as you turn on your RODI, you can turn it off and flush the membrane for 10-20 minutes and that will help. It's way better for the membrane and to keep tds low to make large batches, for you maybe 30-50 gallons at a time would work. That should last you a good two weeks to refill your auto top-off and also water changes. I have a 110g total system volume and I make about 50 gallons every 2 weeks.

Thanks for your explanation! Does "TDS creep" get worse with more on/off cycles? The tough part is that we're not going to have space for a large storage container, so will probably only be able to do ~20 gallons at a time or something like that. So, less storage space will equate to more on/off cycles for the system. I guess it's just a trade off that we'll have to deal with, right?

The situation wouldn't really be any different with a smaller gpd system, would it? I'm thinking probably not, but maybe there's something I don't understand about how the system works.

 

[MatAndPatti]

Oh, and one more thing. No offense to Gary, but get yourself a 75 gpd RODI unit because your 8 gallon tank, has already turned into a 40g breeder and your next step will be a 90-120g tank and you won't have to buy a new RODI!!!!

I'm thinking that it will be quite a while before that happens, but your point is well taken. If I'm going to spend the money, I'd rather only do it once! :lol:

 

[Paradiddle7]

You are fine with a 20g batch. The point is to do batches and NOT hookup your RODI to do top-off duty directly. As long as you have a storage container that is big enough for a water change so that you can fill it all at once OR you are using a storage container for auto top-off to last a few days you are good. If you hookup your RODI to dump directly into your tank for auto top-off and it's turning on 4-5 times a day, TDS creep will be an issue because you will only be putting in maybe 1-2 cups of fluid at a time and that fluid will have a high TDS.

 

[Paradiddle7]

Oh, another thing. Invest the $20 and get a dual in-line TDS meter. I have my sensors after the RODI membrane and after the DI. This tells me the health of the RODI membrane, as well as how much work I'm requiring my DI to do. In order to know the health of your pre-filters, you use a pressure gauge. The pressure will drop when they get clogged and need replacing. When the pressure drops (before your RODI) your rejection rate increases and your output decreases. If your TDS goes up past your membrane, then it's time to replace it. Having the sensor after the DI, shows you just how much creep you have. Most of the time, my system is 2-3 TDS and within 30 seconds, to 2 minutes, it's at zero, so for a large batch, it will essentially be zero. When I start seeing 10-20 tds paste the DI, then I flush my membrane for 30 minutes.

 

[MatAndPatti]

Here's is your drinking water quality report: http://www.mcwa.com/watqual.htm

No signs of chloramine use and we wouldn't recommend more than a 4 stage system for you.

With your tank size I'd go with a 75 gpd system or a 50 gpd system, but because they are about the same price, you might as well get the 75 gpd system, especially if you think you mihgt be getting a larger tank.

Plan on running your system at least once per week.

Thanks Russ! I'm embarrassed to admit that it didn't even occur to me to look for the water quality report online. Duh! :spin2:

A 4 stage is 1 less carbon block than a 5 stage, correct? Is that just because our water looks to be fairly "clean" based on the quality report?

 

[MatAndPatti]

I don't sell 'em and I'm no expert on RO units
HOWEVER
I can tell you that I successfully used a 3 stage (carbon block, micron filter & tfc membrane RO) 25GPD RO unit to provide water for my 75 gallon and 225 gallon aquariums for over a decade.

Even at this point in time I do not have a 5 stage RO unit and I do a 50 gallon water change weekly PLUS produce 30 gallons of RO for kalkwasser (makeup water).

In order to produce 5-10 gallons a week for a 40 breeder (you'll probably end up needing a little more) I would think a 25-50GPD 3 or 4 stage RO unit more than enough.

One of the most important items (IMO) is an auto shutoff for your collection barrel

Thanks Gary! I wouldn't have thought 3 stages would be sufficient based on my complete lack of experience, but obviously it's working just fine for you! Do you get down to 0 TDS with your 3 stage?

Any pointers to good small capacity systems? I can't seem to find any that don't look crummy, or cost nearly as much as a 75 gpd system.

Definitely will get the shutoff and float from the get-go.... especially since I'm not sure if it's going to be anywhere near a floor drain.

 

[MatAndPatti]

You are fine with a 20g batch. The point is to do batches and NOT hookup your RODI to do top-off duty directly. As long as you have a storage container that is big enough for a water change so that you can fill it all at once OR you are using a storage container for auto top-off to last a few days you are good. If you hookup your RODI to dump directly into your tank for auto top-off and it's turning on 4-5 times a day, TDS creep will be an issue because you will only be putting in maybe 1-2 cups of fluid at a time and that fluid will have a high TDS.

Ooooooooooh, I see. Thanks for explaining that, definitely makes more sense to me now! Yes, surely no good to use for direct ato. We'll definitely be doing batches.

Oh, another thing. Invest the $20 and get a dual in-line TDS meter. I have my sensors after the RODI membrane and after the DI. This tells me the health of the RODI membrane, as well as how much work I'm requiring my DI to do. In order to know the health of your pre-filters, you use a pressure gauge. The pressure will drop when they get clogged and need replacing. When the pressure drops (before your RODI) your rejection rate increases and your output decreases. If your TDS goes up past your membrane, then it's time to replace it. Having the sensor after the DI, shows you just how much creep you have. Most of the time, my system is 2-3 TDS and within 30 seconds, to 2 minutes, it's at zero, so for a large batch, it will essentially be zero. When I start seeing 10-20 tds paste the DI, then I flush my membrane for 30 minutes.

Thanks for your summary. I wish that what you just said were part of the FAQ! It's all finally becoming clear to me now! :thumbsup:

 

[block head]

i think the brs 75 is a solid choice. fliter guys recommended a 75 gpd unit for me as well. i use faucet adapter that hooks up in 10 seconds. the unit is then stored untill needed. i usually make ro drinking water and di tank water once a week. i don't have the space to set up a permanent system.

 

[Buckeye Hydro]

A 4 stage is 1 less carbon block than a 5 stage, correct? Is that just because our water looks to be fairly "clean" based on the quality report?

Right. Think of a 4 stage system as a "default" system.

Sediment filter -> Carbon block -> RO membrane -> DI resin

No need for any additional stages unless you have feed water that is unusual.

What sorts of things might nudge you towards adding additional filters? Here's some examples:
Chloramines in your tap water? It is good insurance to add a second carbon stage.

Heavy sediment loads? Might want to add a second sediment filter.

High TDS or high CO2? Might want to add a second or a larger DI stage.

Russ