RO/DI Unit

[jeffro]

Now that I have a second tank, I'm looking at getting my own RO/DI unit. I've been doing some research, but was curious what some of you are using and what your thoughts are about them. I will only be needing about 20-25 gallons per week, so not looking to get too big of a system. Looking at 50gpd units, but it seems like without high pressure I will only get around 1 gallon per hour from them. So it seems that a 75 or 100 gpd unit will be more along the lines of what I would want. My plan is to make it all at one time in a 35g tub that I have, so really only turning it on once per week. Any thoughts or suggestions are greatly appreciated. Also, I am on my own well for water, in case that matters.


Thanks,
Jeff

[Bill S]

Buy one from Buckeye. I've had several of the fleabay types, and finally went to Russ for one. Should have done that years ago... He understands the demands of a reef system - the others just don't.

[corruption]

Agreed -- I picked mine up from Air Water Ice, one of the best purchases I've made in ages... While the 75 GPD membrane may seem like its excessive, the bonuses are that its faster when producing, as well as a higher rejection rate than most other membranes.. If you're gonna be setting up the storage outside, just throw a float valve on the thing, and let it all be automatic -- very nice knowing that 30 gallons of water are at your fingertips if you need it..

-Corruption

[Bill S]

Agreed -- I picked mine up from Air Water Ice, one of the best purchases I've made in ages... While the 75 GPD membrane may seem like its excessive, the bonuses are that its faster when producing, as well as a higher rejection rate than most other membranes.. If you're gonna be setting up the storage outside, just throw a float valve on the thing, and let it all be automatic -- very nice knowing that 30 gallons of water are at your fingertips if you need it..

-Corruption

Man, I hate to disagree...

Several providers have indicated that the lower rejection rate on Dow's 100gpd membrane is a misprint. Allegedly, the rejection rate of the 100 is the same as the 75...

But, the big reason I disagree. I too have a 38 gallon storage tank with a float switch on it. HOWEVER, when an RO system shuts down, there is a slow leakage of less than pure water that works it's way through the membrane. Short cycling the membrane results in more "less than pure" water leaking into your storage container and/or your DI canister. This either shortens the life of your DI canister, or gives you a higher TDS. Depends on how well your DI canister handes the load. That first blast through a DI canister can have a rather high TDS.

SO, the recommendation is that you manually turn on the RO/DI systems to fill a storage unit (until the float stops it), on a once or twice a week basis. There are also top of units that won't switch on until a much lower level is reached - which will run your unit for quite a bit, rather than just running to top off a container or sump.

DANG IT. Forgot this: Those pressure canisters that go under your sink are notorious for this!

[corruption]

Interesting... I haven't noticed any higher TDS affluent in my system... I'll take some measurements before, during, and after filling sometime this week, now you have me piqued :)

As far as the marketable differences between the 75 and 100, their rejection rates are pretty close to identical -- I was more talking about the lower GPD membranes, such as the cheapy 50GPD's that go on the fleabay units.. Rejection rates, and in typical practices, flow rates, are pretty well identical between the 75 and 100GPD membranes -- the bigger issue there being the pressure behind the membrane as well as variance in water temperature determining how much water will actually be produced..

Thanks for the thinking points though, I'll definitely be playing with the TDS meter and my outflow affluent this coming weekend :)

-Corruption

[Bill S]

Those inline meters are really kind of cool. Got one with a used unit I bought - Coralife (UGH, these people build garbage). Has 2 probes. Kind of cool to watch. I have it right before and after the DI. When the RO/DI unit kicks on, the before spikes REAL high. The after spikes to 10-15, and then goes back down to 0-1.

This is why a true "reef unit" doesn't have the accumulator tank.

[corruption]

In-line TDS meter -- just one more of the many things I'd like to add to my collection... if I can ever get my 75gal running! :bigsmile:

-Corruption

[Bill S]

Buckeye sells them for $27, including the fittings. A steal.

[firecoral3msd]

I was told that you will need a separate tds meter anyways, just incase the inline breaks or to make sure its reading right. So why get an inline? Coolness factor? I opted not to get an inline tds because of this. My RODI unit is from air water ice too. One part leaked, the hose that connects to the garden hose. Called AWI and told them about it. They sent me a new part for free, no questions asked. Good filter and company.

[Bill S]

In my case, the inline is nearly a requirement. For the one to my big tank, it goes directly into a 38 gallon storage container. It's not very easy for me to get to the outlet for it - as the container has only a small access hole on the top. I also use the container to mix salt water in, so just measuring the output water from the storage manager won't work. Therefore, the inline. I also have a handheld...

[jeffro]

I'll most likely be getting one from either AWI or BFS, still trying to decide whether to go with the 75 or 100gpd units. I may go with the 100gpd, as I understand I will get less water because of the temp of mine coming straight from the well. I wish I had a garage to set this up in, but I don't so it looks like it will be in my laundry room which is right next to my fish room.

[BuckeyeHydro]

Jeff - how many gallons total in your tank/fuge/sump? With that info, we can recommend a membrane for you.

There is a definite difference in the rejection rate of the different membranes, and you'll see this in the life span of your resin. Higher rejection rate = longer resin life = lower expense to you.

It is best to set up the system so that it omes on less frequesntly rather than cycling on and off frequently (like you'd see if you set fed a float valve in your sump directly from the RODI unit.

Are you on well water of city water?

If city water, do you have chloramines in your water?

Russ

[ShrimpFan]

I grabbed a WaterGeneral RO+DI dual unit off of FilterDirect to try it out. Seems like high quality platics and metal mounting bracket. Tank is good enough, but feels thin, so I'll keep my eye on that. Quality of the water is 99% for the DI 87% for the RO only (the dual unit part means that it has one output for DI for aquarium, one for only drinking water). The RO is supposed to get better one the system's been installed for a week or two. It's already improved in a couple days, so I don't doubt it.

I'm noticing some of ya'll aren't real keen on the ebay specials (of which this is one), so I'll let you know my thoughts as I continue to use it. So far I'm really pleased.

[Bill S]

What is your TDS. That's the determining factor. It should be less than 1. Typically on the fleabay units, they climb to 10-15 within a few weeks.

[ShrimpFan]

What is your TDS. That's the determining factor. It should be less than 1. Typically on the fleabay units, they climb to 10-15 within a few weeks.

Currently my TDS from the RO is 37 (supposed to get down to around 15 after the system has been in use for a bit), and from the DI is 4.

[Bill S]

Currently my TDS from the RO is 37 (supposed to get down to around 15 after the system has been in use for a bit), and from the DI is 4.

Which equals the difference between fleabay units, and Buckeye units.

I've owned THREE cheapo units. Still have one. It's under the sink. Fine for household stuff.

The Buckeye runs water for my systems.

[jeffro]

Sorry for the late reply, but I totally missed that Russ replied.

The total gallons for both of my tanks, sump included is close to 90 gallons. I do 10-15 gallons of water changes per week and another 10 or 12 gallons worth of top off per week. I won't have it on a float system, so I'll probably only turn it on once per week, maybe twice.

I have my own well, so no chloramines, but have not had my water tested other than that.

[BuckeyeHydro]

Given that, I'd go for the 75 gpd system. If you can, get yourself a small, unpressurized storage container with a lid for the di water.

Russ