RODI unit

[caitlynnanne9189]

Im trying to decide on a RODI unit for my build. I will have a 75 gallon reef tank. I also have a freshwater 20g and 3G that I'll use the water for probably. I was looking at the 5stage plus from BRS but it's got a 75GPD rating so I'm back and forth. Can anyone suggest some and maybe tell me how theirs is. I'm not looking to spend a ton of money on it like 300max.

Thanks guys! It's appreciated!

 

[caitlynnanne9189]

No thoughts?

 

[carey]

I just ordered the brs plus system, it's due tomorrow. I have several tanks, I believe I am at 6 all together. And 4 are sw, including a 125g reef tank adn I think the 75gpd will be perfect.

 

[caitlynnanne9189]

I just ordered the brs plus system, it's due tomorrow. I have several tanks, I believe I am at 6 all together. And 4 are sw, including a 125g reef tank adn I think the 75gpd will be perfect.

Let me know how it works Carey. I was a little worried about the 75 GPD only cuz I have no there to mix the water except in the tank when I first fill it unless I can do it in steps. Like 3 different rounds of mixing the water

 

[carey]

It took me 3 days to fill my 125g, it's perfectly normal. You don't have to do it all at once. Plus once you put the rock and sand in you won't need 75g of water due to water displacement. You may end up with 60g or less of actual water. My 29g biocube I believe holds exactly 18g of water.

From my research everywhere it appears that the 75gpd units are the norm and produce the most amount of water the quickest with the least amount of waste water. The plus unit has a gauge on it for water pressure too, I was going to see if I have the 65psi needed to add a booster membrane that would up the gpd to 150 and result in a 1:1 ratio as far as pure water and wast water. This is the addon membrane:

150 GPD Water Saving Upgrade Kit - English

 

[caitlynnanne9189]

It took me 3 days to fill my 125g, it's perfectly normal. You don't have to do it all at once. Plus once you put the rock and sand in you won't need 75g of water due to water displacement. You may end up with 60g or less of actual water. My 29g biocube I believe holds exactly 18g of water.

From my research everywhere it appears that the 75gpd units are the norm and produce the most amount of water the quickest with the least amount of waste water. The plus unit has a gauge on it for water pressure too, I was going to see if I have the 65psi needed to add a booster membrane that would up the gpd to 150 and result in a 1:1 ratio as far as pure water and wast water. This is the addon membrane:

150 GPD Water Saving Upgrade Kit - English

Ok then I'll stick with the one from BRS. My water pressure sucks so I doubt I'll have the needed pressure for the add on but I can always find out later

 

[carey]

when do you plan on ordering? There is a chance that we are doing another brs group buy very soon. like in the next week or so. You can save $20 on that unit, makes it only $180

 

[caitlynnanne9189]

when do you plan on ordering? There is a chance that we are doing another brs group buy very soon. like in the next week or so. You can save $20 on that unit, makes it only $180

I am just waiting for my income tax check and then I'm ordering. I've checked the mail every day! They said 3 weeks and this Saturday will be 2 weeks. As soon as I get that I'm going to get that my lights and my skimmer.

 

[carey]

I would price those things out and if they will be cheaper with BRS you should join the next group buy.

 

[caitlynnanne9189]

I would price those things out and if they will be cheaper with BRS you should join the next group buy.

I found the lights and the skinner I want on eBay for cheaper than BRS. The lights are the LED you have. I'm getting 2 units and the skimmer is a bubble magus that's 239 originally 350.

 

[carey]

I am looking at a bubble magus as well from ebay, thanks to mr x.

Good deal then.

 

[caitlynnanne9189]

I am looking at a bubble magus as well from ebay, thanks to mr x.

Good deal then.

Yep! That's the same thing im doing because of mr x!

 

[Buckeye]

From my research everywhere it appears that the 75gpd units are the norm and produce the most amount of water the quickest with the least amount of waste water. (/quote]

Any residential scale membrane (up to 150 gpd) should be run with the same waste water to purified water ratio: 4 to 1.

The plus unit has a gauge on it for water pressure too, I was going to see if I have the 65psi needed to add a booster membrane that would up the gpd to 150 and result in a 1:1 ratio as far as pure water and wast water.

First - remember that what folks call "waste water" really would be better thought of as "flush water" in that this water serves the important purpose of internally flushing the surface of the semipermeable membrane to keep the membrane from fouling/scaling.

When you configure a system with two membranes in series (the waste from the first membrane going to the "in" port on the second membrane), for this discussion let's say it's two 75 gpd membranes, the system behaves like you have a single long (75 gpd x 2) 150 gpd membrane.

Now - if you use a proper flow restrictor, that is, one for a 150 gpd membrane, you'll have about a 4:1 waste to product ratio. Sounds familiar, right?

If however you don't change the flow restrictor - meaning you keep using the same restrictor you were using when you just had one 75 gpd membrane, then you'll see a waste to product ratio much lower than 4:1. But remember that the recommendation for a ~4:1 ratio comes from the membrane manufacturer. They are telling you that you need about a 4:1 ratio to keep the membrane flushed and keep the membrane from fouling or building up scale. Run the system with a lower ratio and you will foul/scale the membrane(s) quicker than would have otherwise been the case.

Instead of adding a second membrane to lower that ratio, you could have just changed out your flow restrictor ($4) instead. A much less expensive approach to get you to the same endpoint in terms of saving on waste water.

Now, to confuse things just a bit. Filmtec specs call for the 4 to 1 ratio on the basis of assumptions about the water that will be supplied to the membrane. If you have very soft water you MAY be able to get a decent service life from the membrane running at a ratio lower than 4 to 1 (e.g., 3 to 1). Remember that the waste water from the first membrane is about 25% harder than your tap water.

Bottom line: If what you are after is reduced waste water, experiment with a different flow restrictor for $4 instead of messing around with a second membrane plumbed in series.

As a side note, you can also lower the ratio by increasing the pressure delivered to the membrane (with a booster pump), because flow restrictors are sized assuming you are providing factory spec conditions (50 psi and 77 degrees for Filmtec membranes). Increase the pressure and you'll drive more water through the membrane and viola - less waste water. But as I mentioned above, if you do this (just like over-restricting a membrane) - the lower the waste to product ratio, the shorter the lifespan on the membrane.

Makes sense?

Russ