Will I benefit from the brs 150gpd dupgrade?

[Fishbike13]

I would go for the float valve, yes. I don't like the dual membrane setup very much in general, so I would not personally get that. The hobby really seems to like the watersaver upgrade though, so I'll definitely get outvoted on that one. But, regardless of how little my vote counts, I submit it anyway.

I guess i don't understand why you don't like it. Since the water flows through each membrane in series, they still have the same amount of flush water do they not? It is simply just passing the higher tds water from the first membrane through the second which in theory is still producing at a 3:1 ratio, the flush water ratio is still the same, just more concentrated TDS. It makes sense in my head, i may just not be articulate enough to put it into words.

Either way I do appreciate the input from all parties.

 

[chipmunkofdoom2]

I guess i don't understand why you don't like it. Since the water flows through each membrane in series, they still have the same amount of flush water do they not? It is simply just passing the higher tds water from the first membrane through the second which in theory is still producing at a 3:1 ratio, the flush water ratio is still the same, just more concentrated TDS. It makes sense in my head, i may just not be articulate enough to put it into words.

Either way I do appreciate the input from all parties.

My main objection to the water-saver kit is that I don't think it's cost effective in most cases where it's applied. I don't think that, once you account for the cost of the tap water and the extra parts, the systems are actually cost effective.

To my first point about cost. As I mentioned above, if you need 100 gallons of RO water per month, you'll waste 400 gallons at a 4 to 1 product ratio. The numbers vary from source to source, but generally, tap water is said to cost $1.50 to $3.00 per thousand gallons in the US. Even if we use the high figure, that's only three tenths of a cent per gallon. Those 400 waste gallons are only costing you $1.20 per month. Annually, that's about fourteen bucks. Let's say you could cut that in half with a water saver. You're only saving sixty cents per month and a whopping $7 per year on waste water. A water-saver upgrade costs $60. That's an eight and a half year break even period in terms of cost of water alone, and that's if you need 100 gallons of RO water a month (that's 40 gallons for topoff as well as two 30 gallon water changes). Many reefers probably need less than that, so the break even time is even longer. That also doesn't account for needing to replace two membranes, or the fact that membrane 2 will likely need to be replaced more frequently since it's being fed with the brine from membrane 1.

My second objection is that it's almost impossible to get a perfect 4 to 1 waste to product ratio to each membrane. You can make sure that the total output of the system is about 2 to 1, but this doesn't guarantee that pressure and flow are split exactly evenly between both membranes. So now, instead of properly maintaining and maximizing the life of one membrane, two membranes may or may not be getting optimal pressure and waste water flow. Which means more frequent replacements, lower rejection rates, or both. Which adds up to more costs.

There may be some cases in which a water-saver upgrade makes sense. If you have exceptionally high chlorine/chloramines and you want to make your prefilters do as little work as possible, a water-saver upgrade may help lighten the load on your prefilters. You really should do some detailed testing to make sure you're actually saving money if this is your use case though. After buying the upgrades and replacing membranes, I really don't think you would save much money. There are legal limits for chlorine and chloramines in the US, so there's a limit to how much savings you will get by maximizing the life of your carbon blocks.

If you have really expensive water because you live in an area which has water shortage issues, a water saver upgrade again might make sense. But again, depending on the website you search, $3/1000 gallons is the high average. Considering that a family of four uses an average of ten thousand gallons of water per month, it doesn't seem very sensible to be so worried about the 400 gallons of waste water you might produce in a month with your RO unit. The best you're going to do is cut that small percentage in half. If your RO membrane is only 5% of your monthly water usage, I'd look at cutting some of the other 95% of usage if I needed to save water.

A water-saver kit will produce water faster, probably around 6 gallons per hour. But, even this system would take almost 4 hours to produce 20 gallons of water. If you have an emergency and need 20 gallons of RO water right now now, the best option is to have a reservoir where some is already made, not to have to wait for "only" 4 hours instead of the 8 with a single membrane system.

Sorry to get so off topic. But that is why I don't like the water-saver upgrade. I don't feel like it's necessary or effective in most cases.

 

[Whipples]

The other key element at play is source water quality. If you have high TDS source water, the water-saver upgrade will actually cost you long term as you run the brine output from the first membrane into the second, which is now ~15-20% higher in TDS than the source so you are actually running worse water through the second membrane. This second membrane is then able to cut that down, but the rejection rate between the two membranes will be different as you will experience pressure loss in the system (more plumbing, more restriction, more media to run through = more pressure loss). You can easily measure this by having a T on the line from the first membrane output and the second membrane output. For example: I run a dual membrane system and my source water is about 250-280 TDS. Reject water (or brine water) from the first filter is now about 300 TDS going into the second membrane, and combined output is about 7-10TDS before the roughing stage and DI media. Thats 96-97% combined rejection, however the first filter is more efficient than the second (keep in mind this is at a combined 3:1 waste ratio).

Those mechanical flow restrictors are not guaranteed and are why folks get led to believe they are truly saving water when in most cases your restrictor is now out of whack compared to the pressures and volumes you are running. They also operate assuming 77F source water and a certain PSI, while many of us run different source temps and PSI so while it says it is a 2:1 or whatever ratio, it may be much different within your actual system. You should be using a capillary style flow restrictor for a 150GPD system if you use dual membrane, and adjust it based on your actual observed ratio over a minute of production between product and source water (RO out, wastewater out, no need for DI stages for this measurement). This is truly the only way to make sure you are maintaining an appropriate ratio. I have two, one for summer and one for winter to account for the changes in source water temperature.

Again, if you are seeing close to 1:1 water to waste ratio when adding a second membrane, it WILL fail on you quickly. Flow restriction (and pressure) is significantly more important to water quality as that rejection water is what is cleansing your membrane and pushing rejected solids out of the system, which is the whole purpose of the filter! I strongly encourage folks who are running under 3:1 waste to product ratio to reconsider and adjust your restriction to improve water quality and significantly extend membrane life. By taking 4:1 waste out of the first membrane and pushing it to a second membrane, and therefore combined waste ratio is 2:1 you are really just taking concentrated waste water and blasting the second membrane, at a lower pressure, and with less waste water to cleanse the membrane. That goes against the fundamental concept that allows an RO membrane to function properly.

Adding a second membrane should really just be considered for making more water and faster, and not in saving water as that goes against the principles in which an RO membrane functions. High pressure and at least a 3:1 waste ratio will allow your system to operate at a much higher rejection rate and prolong the life of RO membranes AND DI media. If you run the second membrane, I strongly encourage you to look at Spectrapure's roughing stage as it does not exhaust as fast as other DI media, but needs standard DI media to follow it to correct for the roughing stage. This can save more money on DI media for those with challenging source water issues.

If you are trying to save water, I would really recommend running the waste line either into a reservoir and use that on your yard, or run your waste line into the washing machine and do laundry with it (assuming you know how much waste you produce and can accurately time it to prevent overfilling!). That way I am using all of the water I am being charged for and do my water cycles based on laundry .

 

[Fishbike13]

Theres the info i was looking for. I'm a mechanic, and sometime these details are lost on me, but now it makes a lot more sense. I also realize that the water saver is really just splitting hairs for my purposes, where it would seem the only benefit (however short term it may be) is that i would get more water faster, but the reservoir makes more sense as i use it to top off my cichlid and planted tanks between water changes. I will be forgoing the water saver, and keep a good flushing schedule before and after use to maintain the membrane i have.

Do i dare ask about the benefits of running a second DI stage to help account for the first DI stage depletion and maintain contact time with the resin?

If i have come across as argumentative, that's not my intention, and again, i do appreciate all of the replies.

 

[Whipples]

You came across just fine . I would argue that running a 3 stage DI (anion bed, cation bed, mixed bed) is best and what I run as it allows more time for the water to run through the media and do its thing. BRS has a great video on it.

https://www.bulkreefsupply.com/vide...ates-mixed-or-single-bed-di-resin-maybe-both/

 

[Buckeye Hydro]

If what you want to do is cut down on the ratio of waste water to purified water, you don't need a second membrane to do that. Just change your $4 flow restrictor. Be aware of the implications of doing that.

Russ