More Effecient RO/DI

[davefan13]

hey everyone,

i am still in the planning stages of my first reef tank, a 55 gallon with 2 175watt metal halides. anyway, the water that i get in my town is relatively expensive, and i would hate to run a ro/di unit that wastes four gallons for every one that i would get. I was thinking that what i could do was to take two large rubbermaid trash cans, like the 33 gallon ones. i would fill up one with water to be purified, and one would be empty, for the ro/di water. i was thinking taht i could just run a pump in the bottom of the trash can to the ro/di unit, and have the waste water run back into the trash can with the pump. This way, eventually, most of the water would get filtered to be worth for my tank.

anyone who has done this, or knows ways to make ro/di systems more effecient, please help me out here.

thanks

[davefan13]

bump

[Icefire]

get 4 membrane, you'll get a 1:1 ratio.

[davefan13]

really? i have heard so much stuff about "all good ro/di setups will get a 4:1 ratio" anyone else have experience with this?

[bergzy]

Zero Waster RO Unit

expensive for what you get but truly is zero waste.

i had one but after two years, the waste water pump that pumps into the hot water line finally broke down. thank goodness for the great costco return policy!

[davefan13]

wow, that looks great. I may go with that. Does it still give you 0 tds?

[Black71gp]

I had one.. problem was the hot water would go back into the cold water line and hot water would then go to the RO membrane.. could not get membrains to last more than a fre months...

[BeanAnimal]

The zero waste system is not that great of an idea when it is all said and done. It is actually a rather bad idea.

Depending on your local water cost, water pressure, and the amount of water you make... Adding a second (or third or fourth) membrane may or may not make sense. In many cases you could easily spend more for the added efficiency than you will ever save.

Your tank and water needs are rather small. Depending on your pressure and water cost, I would bet that adding a membrane is not worth the cost.

[AZDesertRat]

Your idea is not really sound in that you will need a pump capable of 50-60 psi to feed the RO membrane and energy costs will more than offset and water savings. You will also be concentrating the TDS higher and higher over time which will eventually cause the membrane to fail, you need fresh water to flush the contaminants away from the membrane not concentrated brine.

The "zero waste" system has lots of shortcomings including a very limited capacity, elevated TDS in the homes hot water piping, electrical costs and a shortened hot water tank lifspan.

Spectrapure is developing a 1:1 system that should be on the market in a few months, they have been running in beta testing for over 6 months now and look to be very promising. I have seen it in action a couple of times and its the slickest thing since sliced bread!

[datablitz]

another alternative that i have seen used is called kold steril. it is similar to a no waste ro, but it is different because its not ro? i think. its also expensive, but there is no waste.

[silverwolf72]

I thought a reason for the waster water was to help keep the membrane clean. I'm still a little lost on the RO thing.

[AZDesertRat]

You are correct, the waste is what flushes the membrane. Putting multiple membranes in line normally uses the waste fron the first to flush the second and so on. This contributes to shortened membrane life of the downstream membranes. The zero waste system is not really zero waste, it takes the 4:1 waste stream and puts it through a booster pump and injects it into your hot water heater. Again not the best option.
The new Spectrapure system will use some sophisticated equipment to monitor membrane condition and automatically flush the membrane using DI water so 4:1 will not be necessary since the flush water is so pure.
The kold steril is not all its cracked up to be. Besides being expensive it will not give you 0 TDS water. It is somewhat selective on what it removes but not nearly as efficient as they try to make you believe.

[davefan13]

ok. I am going to try and stay under 200 dollars for my RO/DI, but i don't know if that will work for my needs. Kold Seril is out for me, as is the zero waste water unit because they aren't that great, and they are expensive. is there any way that i can hook it up to, say, my washing machine or something similar where the waste water will be used for something else. I have grown up here, and learned about the expense of water and not to waste it. This is basically what i want to do.

any more comments would be appreciated. also how would i be able to measure my psi and tds from my water. are sinks usually capable of producing the 50-60 psi needed? if not, what do i need to do?

thanks a lot!

[BeanAnimal]

You can certainly drop the waste hose in the washer. I did for a few years until we got a front loader. Now I don't bother.

You can also use it to water the lawn and plants. Use it for anything. You could actually drink the stuff.

I know you don't want to put it down the drain, but it is really a very small part of your water usage. Take a few minutes less in the shower each day and you will save more.

[wife no likey]

I just posted this in the general forum, but as an FYI, I just got done redoing my whole setup, and am pretty happy with the outcome.

I ended up adding a booster pump (50$ off eb@y - it's an 8800 knockoff) running at 75psi

I also managed to get a box of a bunch of RO parts off of there as well that included a 100gpd membrane, housing, and a permeate pump. (I have a bladder tank)

I'm now running the 100gpd membrane in series w/ my 75 filmtec first in line.

Running with a 800 restrictor, I'm getting about 1:1.5 with a post RO TDS of 3. My source is about 190-200.

[davefan13]

ok, i also have a front loader washer. we got those BECUASE of the price of water and how they use less.....and becuase we needed a new one . i am just figuring that if i need to make up 65-70 gallons of water to start up my tank..... *pulls out calculator and punches in numbers*......that is 260 gallons of waste water, 65 of pure.....which is 325 gallons, most of which i would not use. then if i do a 20% water change weekly and add a gallon of evap. daily....thats 20 gallons extra. . . . 80 of which would go down the drain....which is a total of about 5500 gallons of water 4400 of which is waste.

if you really look at these numbers....it kinda bites you in the a**

[davefan13]

pennilessreefer.....ok. that sounds great. i have a feeling that i will end up retrofitting my RO/DI also. what kind of filter did you start off with and how much do you think that all of the parts together have cost?

[wife no likey]

one of the primary factors is where your pressure coming in runs.

I'm at a high point in my area, and only was getting about 35psi most of the time, so the booster pump added some cost. If you are at 60 or 70psi I think you can skip the booster.

If you have a bladder tank, then I think that the permeate pump is a very wise investment. As you fill your bladder tank fills, it decreases the pressure delta across your membrane killing performance. The PP uses the pressure of the waste line to counteract that.

When it comes to adding the second membrane, I got this one cheap, but I suppose that you could get the membrane and housing new for about $60.

[wife no likey]

oh and to actually answer your question


I started off with a "water general" three years ago, and have since replaced my membrane w/ a 75gpd filmtec, and I now run a 1 micron sediment followed by a 2 and then .6 carbon.

not counting replacing membranes and filters, I suppose that I have about an extra $100 worth of pieces invested, but I wait to find stuff cheap.

[AZDesertRat]

penniless, you should probably switch the membrane positions for best quality. The 100 is normally not as efficient as a 75 so you would want it first in line so when the 125% concentrated waste stream from the first one goes through it gets treated more efficiently by the second one. Let the less efficient one treat the normal TDS concentration and the more efficient one trate the concentrated TDS.

Normal household pressures nationwide are in the 50-60 psi range with most utilities trying to stay closer to the 50 for power savings on pumping equipment.

Yes 5500 gallons seems like a lot but in the grand scheme of things it only costs me about $10 for that much water here in Phoenix and once it passes through the WW treatment plant it goes to cool a nuclear plant. From there it evaporates, rains back down and starts the cycle all over again although I wish it would rain back down here in AZ and not somewhere else!

[Icefire]

for 200$ I guess you could manage a 2 membrane system. It would be maybe 2:1

[davefan13]

haha, i see. But, you live in a large city.....i live in a small town of about 6000. AND to make matters worse, our town supplies our water and gas, which makes it more expensive.

oh well, i guess it comes with the whole "living in a small town" package

[BeanAnimal]

can you let us know your water cost?

[wife no likey]

AZ,

yeah I was going to but my setup looks like a ball of spaghetti now and I didn't want to take all of it apart.

I'll switch them around when I finish some of my other projects.

Pete

[AZDesertRat]

Sounds like mine! I just did a piggyback membrane too plus I have an autoshutoff valve, two pressure gauges, two dual inline TDS meters, two RO faucets, one DI faucet, a 14G pressure tank, ice maker etc...... I need to carry it back over to Spectrapure and let them clean it all up for me!