Making salt water for 180 gallon FOWLR?

[Neptune 555]

I am upgrading my 75 gallon reef to a 180 gallon FOWLR. I have been making salt water with RODI system that wasted 90% of the water... this has been fine I think for my water changes when dealing with a 75 gallon. It makes 3 ish gallons an hour. slow....

NOW that I am upgrading to 180 I am wondering what do people do to make water?

Option A: Use tap water now b/c not a reef? I do this with my Qt tanks?
Option B: Better system?

[Spyderturbo007]

I definitely wouldn't use tap water. How often do you do water changes? Even at 3g/h, you can still make 72g in a day. If you're doing a 10%/week water change, you only need 18g in a week.

Obviously the initial fill will be slow, but I'm wondering if buying a larger system would be worth the money since you'll really only need it one time.

[OpPrime]

Bulk reef supply sells this upgrade kit!

Basically taking the wate water from the RO membrane and running it into a second to membrane giving you a chance to get more pure water out of instead of puttingit down the drain. I noticed my GPD is up and I am not eating nearly as much water.

Hope this helps!




Sent from my iPhone using Tapatalk

[mcgyvr]

Originally Posted by Neptune 555

I am upgrading my 75 gallon reef to a 180 gallon FOWLR. I have been making salt water with RODI system that wasted 90% of the water... this has been fine I think for my water changes when dealing with a 75 gallon. It makes 3 ish gallons an hour. slow....

NOW that I am upgrading to 180 I am wondering what do people do to make water?

Option A: Use tap water now b/c not a reef? I do this with my Qt tanks?
Option B: Better system?

Typically RO systems make 1gallon of "good water" and exhaust 4 gallons of "bad water" to do so.
That ratio is usually fairly consistent no matter what "gallon per day" amount membrane you have.. Sounds like you have a 75GPD membrane..

As stated you can upgrade the membrane (and a few other critical parts like the flow restrictor to match that membrane) to a higher gallon per day system but don't expect just that alone to change the amount of bad to good..
There are ways to improve the ratio though..

One can most certainly use a 75gpd system with a larger tank.. You are just going to take a few days initially to fill it up but after that you most certainly do not need to be making anywhere near 75 gallons a day to maintain it..

[alton]

https://www.bulkreefsupply.com/4-sta...ef-supply.html
And store it in a 60 gallon water barrel

[moondoggy4]

I do not water my backyard anymore but I still have one tree that I like, so I run my waste water from the my RO/DI machine to my tree. So no wasted water.

[ibryson]

I'd definitely consider upgrading your RO/DI system. It'll pay for itself in the long run and ensure proper water quality. Bulkreefsupply offers prett great deals and black friday sales are coming up. They usually run decent sales during that time

[mlb75]

Adding the second membrane like was mentioned above is the best thing you can do, waste stays the same but basically doubles the output for the same waste. I saw a huge difference when I switched mine around like that.

[McPuff]

I have a 300 gal tank, run a 75 gpd RO/DI system, and store in a 65 gallon Norwesco. Only make about 30 gal of saltwater at a time. Works well for me.

[tkeracer619]

Originally Posted by mlb75

Adding the second membrane like was mentioned above is the best thing you can do, waste stays the same but basically doubles the output for the same waste. I saw a huge difference when I switched mine around like that.

Then you are using an improper waste ratio. When adding a second membrane you need to change the restrictor so you still get 4:1. You can always run it less than that but the membranes will foul quicker. Production should certainly increase.


To the OP, I'd avoid tap but plenty of people do it. You can run a lower waste ratio than 4:1 but you will foul membranes quicker. If you have a softener you can run a lower waste ratio without much issue. I wouldn't add a second membrane though if you are running 9:1 I would check the flow restrictor. How old is the system and what is your pressure. The membrane may be fouled.

[mcgyvr]

Originally Posted by tkeracer619

Then you are using an improper waste ratio. When adding a second membrane you need to change the restrictor so you still get 4:1.

Technically 4:1 is "improper"... As datasheets/testing (calculated lifespans,etc...) for membranes assumes a 15% recovery rate which is like 1:6.667

And there are 2 different ways a dual membrane setup can be done..
One will achieve a reduced amount of waste water and one increases the production rate.. (serial/parallel)

One can also just change the restrictor and not run dual membranes and increase the recovery rate and yes that "may" reduce the lifespan of the membrane but depending on the cost of your water that may be something that completely makes financial sense where waste water costs over time is greater than the increase membrane costs which is very easy to achieve with todays city water costs.. ($35 for 1000Gal,etc....)

[mlb75]

Why am I wrong, as long each membrane has it's own correctly sized flow restrictor what's the issue??? The way I have mine plumbed is that the "waste" water from the first membrane feeds the second membrane and the TDS of the "good" water from each membrane is I believe identical coming out. I plumbed it that way specifically to cut my waste water in half. Just to be clear there is a flow restrictor and flush valve between the first membrane waste output before entering the second membrane and another regulating the flow of the second membrane and will agree if they weren't in place there could be problems. I've simply recycled the "waste" water from the first and to be honest if I needed more water wouldn't hesitate to add another membrane fed from the waste of the second. My only question adding successively more membranes in that manner would be potential issues due to pressure losses or back pressure affecting the membranes but with two there seem to be 0 issues.

[tkeracer619]

In a series set of membranes you aren't supposed to have a flow restrictor on the output of the first membrane. The restrictor on the 2nd membrane works for both membranes.

You are also supposed to still have a 4:1 ratio with the two combined in series.

Sure, you can crank it down and reduce the life of the membranes, you also increase TDS so will burn more DI. Most people think you should have a 2:1 ratio with dual in series membranes, it's an easy misconception, if not an outright marketing ploy. If less waste is your goal no reason you can't sacrifice a membranes life span. I have a water softener and still run a 4:1 through dual 99% spectrapure membranes. I am getting close to 2000gal through the system before changing DI carts.

Here is a quote from Russ at Buckeye

Originally Posted by Buckeye Hydro

We feel it is misleading to tell people they can cut down on waste water by adding a second membrane. Here's why.

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

And from Bruce at Spectrapure.

Originally Posted by SpectraPure

Adding a second membrane is typically done in series, and has been for years. That is nothing new.
However, one must install the appropriate flow restrictor or risk premature failure of the downstream membrane as the hardness components collect on the downstream second membrane.

Essentially, nothing is for free, ie; a second membrane requires proper waste ratios or risk premature membrane failure. You can experiment first with simply adjusting your existing flow restrictor to reduce your waste and see if you still have suitable life of your membrane, and performance.


That said, if your local water conditions allow you to run with less waste water and you obtain suitable production and rejection, than good on you.
bruce

[Percula9]

I would just buy salt water already made for the initial set up.If you want water upgrade to a DI tank.No waste water.