Head Swimming about RO/DI

[DSDoyle]

Hello,

My head is swimming regarding RO/DI systems. I am in the process of setting up a 150g reef. I am not sure what I should be looking for with regards to a good RO/DI system. I have been told to get at least a 5-stage (I understand 7 would be better). I get that. What I do not understand is what capacity system I should get. Of course, I will need to produce enough water for the initial setup, but after that I am not sure. I spoke to someone over the weekend and I was telling him I am thinking something that could go up to 25 GPD would be sufficient. He advised me that if I do not have the system in production 24/7, the system gets "bogged down" so to speak requiring a flush at the start. I do not see any systems that go below 80 GPD.

Please advise.

Have a great day,

Don

 

[SnoopyDaPimp]

150g might take a day and change to fill. My ROD/I is 75 gpd with a rejection rate ~2:1. You don't need a giant system, mine supports a 110g and a 46g just fine. I make water twice a week when I do my water changes that are offset (this is so the water doesn't sit in the filters, etc...). I make ~40g ROD/I a week and save my rejected water for cooking, water jugs (drinking/dogs) and ultimately the pool when I start to make water again. Just need to make sure that you have good water pressure after your RO membrane (45-60 psi)

 

[thegrun]

I would get at least a 75gpd system, it's going to take too long with a 25 GPD system. Some of the "bells and whistles" are really must have items IMHO when it comes to an RO/DI system. The things you want:
Pressure gauge, at least a duel TDS meter, RO flush valve.
A duel canister for DI resin will pay for itself in less than a year as you will get a lot more life out of your DI resin if you use two canisters.

 

[DSDoyle]

I understand, but the guy I was speaking to told me if I do not have the RO/DI producing all the time the membrane will not last as long.

Your thoughts?

:spin3:

 

[Isaacs55]

I would go with a 100gpd or 150 gpd system. You'll thank me later. The bigger the better. Getting a smaller unit will be insufficient like you said bogged down because you'll be trying using more water then what you'll be producing. I have a 150 gpd unit and my DT is a 40 breeder and a 20 long sump. As far as the stages go, 5 stage is ideal with a bigger unit. You can go past that and it will prolong the life of your unit.

 

[CStrickland]

I understand, but the guy I was speaking to told me if I do not have the RO/DI producing all the time the membrane will not last as long.

he's talking about "tds creep."
the idea is that when you turn off your unit, there is some water still inside that is only halfway treated. as it sits between uses, the dirty water can get pulled onto the clean side of the filter, so on your next use the first couple minutes of flow are coming into the Di resin dirtier than they should be. that's bad because it wears out the Di resin faster, costing you money. you can tee off before the di and flush it or I just run the unit for a couple minutes with the whole Di can removed.

when you compare rates keep in mind that it really is gallons per day, a 25 gpd system will literally take an hour to make a gallon of water.

here is a good post that I came across the other day, it explains some of the rodi mechanics in plain english, which is nice
http://www.reefcentral.com/forums/showthread.php?t=1735396

welcome to the forum!

 

[shifty51008]

Also keep in mind rejection rates of the membrane. The 75gpd membrane has a 96-98% rejection rate where as others can have in the low 90's. The better rejection rate of the membrane the longer your di filters will last. My system is around 200 gal total and my 75gpd unit is plenty good for my tank and the wifes drinking water

 

[Buckeye Hydro]

Hello,

My head is swimming regarding RO/DI systems. I am in the process of setting up a 150g reef. I am not sure what I should be looking for with regards to a good RO/DI system. I have been told to get at least a 5-stage (I understand 7 would be better). I get that. What I do not understand is what capacity system I should get. Of course, I will need to produce enough water for the initial setup, but after that I am not sure. I spoke to someone over the weekend and I was telling him I am thinking something that could go up to 25 GPD would be sufficient. He advised me that if I do not have the system in production 24/7, the system gets "bogged down" so to speak requiring a flush at the start. I do not see any systems that go below 80 GPD.

Please advise.

Have a great day,

Don

Don - be happy to walk you though selecting a system and can answer any question you have. Easiest if done over the phone. There are some misconceptions in your post and others in this thread.

Russ
513-312-2343

 

[Monte26]

Check out BUlk Reef Supply's value plus rodi unit. It's 75 gpd and I absolutely love it. I don't produce water 24/7, but I do flush the membrane before and after use.

 

[stingeragent]

Get a 75gpd off BRS as previously mentioned. Great unit. Then all you need is a 30+ gallon brute trash can, and you'll be set.

 

[uncleL]

Go to local feed store and get some pickel barrels 55g...I got 2 $40.00!!!

 

[CStrickland]

There are some misconceptions in your post and others in this thread.

It would be helpful for the rest of us to know which info in the thread is incorrect. Unless it's like a sponsor rule where you aren't supposed to debate stuff, that'd be understandable I guess.

I heard buckeye makes good units. I'm real happy with my spectrapure refurbished 90gpd too.

 

[stingeragent]

I'll agree with CS on this. What are the misconceptions you are talking about?

 

[oldbones]

I have a 150gpd unit purchased from Melev's Reef. It fills a 5g jug in 32 minutes and I love it.

I have 3 tanks in the house, total volume about 100 gallons. Once a week I make a 5 gallon jug to refill my ATO reservoirs, and 10-20 gallons into my brute saltwater mixing barrel. None of that is automated, so I appreciate that it goes fairly quickly.

 

[splix]

I just filled a 155 gal tank with a 30 gal sump on a 50 gal/day membrane in my 6 stage ro/di system. I started sat afternoon, I finished Wednesday afternoon. Huge pain in the *** honestly because you dont want to pour the RO/DI water into the display tank when filling from start. You want it to go into a different reservoir to mix the salt in. My "other" reservoir was 30 gallons. I would have to time my life around it so it wouldn't overfill, etc. I didnt want to turn the water off because I wanted to get water made and finished with also. haha

Now that it's up and running it's not that big of an issue, but man I did not enjoy the 0% to 100% fillup with a 50gal/day system. I would get as close to 100+gal/day if possible.

 

[shifty51008]

It would be helpful for the rest of us to know which info in the thread is incorrect. Unless it's like a sponsor rule where you aren't supposed to debate stuff, that'd be understandable I guess

well 1st off the number of stages, more doesnt always mean better.

2nd "if the unit doesnt run 24/7 it will bog down" that is deff not true.

3rd he cant find any units that produce less than 80gpd. There are plenty of units that produce less than 80gpd. The reason 75gpd units are most popular is because the membrane's have the best rejection rate over others

 

[CStrickland]

yeah, I get where OP was mixed up. Buckeye's post mentioned inaccuracies in the OP as well as "others in this thread," I was curious what the others were. If that gets aired out here then everyone learns and we aren't passing along bad info to the next person with these (not uncommon) questions.

 

[shifty51008]

Well another said to get a 150gpd unit, the bigger the better.

That again can be false. There are lots of threads of people running dual 75 gal membranes to achive this which doesnt always work out to be better than if someone was to run a single 75gpd membrane.

Hopefully russ will chime back in here though, he is much smarter about this stuff than i will ever be.

 

[Buckeye Hydro]

People sometimes are sensitive re being told their info is a little off course, so that's why I didn't do this right off the bat. But since you asked...

Shifty hit on a number of these.

He advised me that if I do not have the system in production 24/7, the system gets "bogged down" so to speak requiring a flush at the start.

RO systems typically do not run 24/7. It's ok if they do, but certainly not required. At the other end of the spectrum, they should be configured such that they run at least once a week. Manually opening a DI bypass when you first turn on any RODI is a good idea. Leave the bypass open until the TDS Creep water has passed and the TDS of the RO water TDS is where it should be. This approach doesn't always work - such as in situations where the RO system turns itself on and off. There are work-arounds.

I have been told to get at least a 5-stage (I understand 7 would be better). I get that.

Another misconception especially common with uninformed vendors or new users. In most situations, 4 stages is what you need and will give you the best bang for the buck. Sediment->carbon->RO->DI. Add more prefilters (the filters that touch the water before it reaches the membrane) if for instance you have high sediment loads, or if you have chloramines. You can also have multiple RO membranes, and multiple DI stages.

I do not see any systems that go below 80 GPD.

The membranes used in the "residential scale" RO systems common in this hobby are called "1812 membranes." Meaning they measure, nominally, 1.8" in diameter and 12" long. 1812 membranes are available in lots of capacities from lots of manufacturers, including 24 gpd, 36, 50, 75, 100, 150, 200. Among manufacturers and membranes the factory spec rejection and pressure vary, so pay attention to the fine print. Also - the 90 gpd membranes you sometimes see referenced ARE 75 gpd membranes where the vendor is telling you to run it at 10 psi higher than the factory spec. ANY 75 gpd membrane will produce 90 gpd at 10 psi over the spec.

My ROD/I is 75 gpd with a rejection rate ~2:1.

This post confused "rejection rate" and "recovery." These are two entirely different things. More on this if there's interest. Remember YOU can control the amount of waste water your system produces by changing a $4 part.

A duel canister for DI resin will pay for itself in less than a year as you will get a lot more life out of your DI resin if you use two canisters.

Having a dual DI setup doesn't extend the life of your DI resin cartridges.

I understand, but the guy I was speaking to told me if I do not have the RO/DI producing all the time the membrane will not last as long.

Not true.

I would go with a 100gpd or 150 gpd system. The bigger the better.

Not necessarily. Higher (100 gpd and up) may have lower rejection rates and or higher pressure requirements. More on this if there's interest. Faster membranes may not be needed, especially if you have some storage capacity for the DI water.

No offense to anyone intended if I quoted you above!

Russ

 

[homer1475]

This post confused "rejection rate" and "recovery." These are two entirely different things. More on this if there's interest. Remember YOU can control the amount of waste water your system produces by changing a $4 part.

Russ

Super curious about this.

I'm assuming rejection is the water being "rejected" by the system, or in laymans terms, the water going down my drain and not being used by the system? Please correct me if I'm wrong. Not sure what you mean by recovery. I had always assumed anything not being used by the system is "rejected water"?

I'm also going to assume the $4 part would be the flow restrictor?