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Preparing for a Grow Rack -- Reverse Osmosis Units

Joined
Nov 29, 2008
Messages
497
Location
Twin Falls, ID, USA
Didn't find anything in the Carnivorous Plant Articles section about Reverse Osmosis units nor anything with a quick search, so I thought I'd ask.

As I prepare to install a plant rack and more plants, maybe even a mini-bog outside, I find myself running low on water. A local Fred Meyer has one of those RO Water Filter stations, but I do not drive and walking 5 gallons of water home is not a super appealing proposition. Bringing home water 1-2 gallons at a time is working out pretty well so far but with more plants, that is becoming a losing position.

What I have actually been looking at lately is a Reverse Osmosis unit. However, as I currently live in an apartment, it would have to be a unit that I could connect to a tap source and not an under sink or garden hose unit.

The one I was looking at first was the AquaWizard (No opinion as to the store, just a link to the product):
http://www.momentum98.com/aquawizard.html

It seems to be about what I need, with it hooking up to the tap directly and filtering water on out. The speed seems a bit on the low side, with it taking 90 minutes to make 1 gallon of water, but for my use, that would probably be plenty.

I mentioned this on another forum and someone pointed out for the price of that system, I could purchase a "real" RO system. The one he said he owned was the following (again, I have no opinion on the store, just showing the product):
http://www.purelyh2o.com/product.php?productid=16210&cat=249&page=1

This one also has a faucet adapter, but is a 75 Gallons Per Day system. Now, the other system assumes you would need to replace the filter in 6 months, presumably this system would need the same -- but if I am not using it at anywhere near capacity (I cannot imagine needing more than 1-2 gallons a day, if that, depending on if I make a minibog or not -- a minibog will add to my water usage rather extensively), the filters would likely last me a good long while, correct?

Another local friend who keeps tropical fish also suggested purchasing a RO filter system from a local tropical fish store, but I am unsure as to the effectiveness of one of those systems. Most of them that I saw through a quick glance are Ionization systems or other types of filtering, not RO.

So, any advice for a slightly crazy newbie looking into moving beyond gallon jugs of water from the local WinCo? Perhaps I should buy a TDS system before making the plunge?
 
Joined
Dec 23, 2008
Messages
643
Location
Sonoma County CA
I just went through these same issues when looking for a RO unit. I just did some basic research on RO units and then searched every where to find the best deal. In fact I just bought what I think is the best deal around. Here is where I bought it http://www.drsfostersmith.com/product/pet_supplies.cfm?c=3578+4395 it is the Pure-Flo II RO Units 50 gpd 3-stage. They also had a very good RO unit selection guide and FAQ's. The most important thing you need to know is RO units with less filters, filters out less contaminants from the water. In fact the one I choose has both RO and DI. I too do not need 50 gallons a day so I assume just as you I will not need to replace filters every 6 months. This will have to be a trial and I will check with a TDS meter Every month or so to figure it out. It is also a little more portable then some of the others and can be hooked directly up to your faucet. Also I just bought a grow rack as well. First I bought one of the small racks with the plastic zip up cover. I returned it as I thought it was not very sturdy. I did find some people that have used them with success. It cost me like 80 dollars. I went to my local target and got some metal shelving for 25 dollars (it was also on sale, normally 30-40 dollars) that is much stronger (250 lbs. per shelf, 750 lbs. total). Anyway I hope this helps as all this was about 2-3 months of research for me!
 
Joined
Oct 12, 2001
Messages
4,641
Location
Far Away NY
The aquawizard is very expensive for what you get.. you pay alot of the simplicity I guess. It is also quite small and I would guess it will take a long time to make a gallon of water. I could find no stats on it's rate.

Some basics on RO systems. TFC (thin film composit) membranes give you very clean water but are susceptible to chlorines in the source water. So you MUST use a carbon prefilter to protect the membrane IF you are on treated water. It is also a good plan to have a sediment filter before the membrane 1micron is best.. the cheap ones go up to 5 or 10 micron. Ideally you have the carbon and the sediment prefilter seperate so you can just change the one that needs changing. Cheaper units combine the two into a single filter. If you have really clean paticulate free water though then a single 1 micron carbon block prefilter will work fine as it will not get clogged by suspended particles by the time the carbon has worn out.

Ratings for water production are also done under optimum pressure and temperature. The higher the pressure and the warmer the source water the more RO water you get out. DO NOT count on geting anywhere near the listed production using household water temperature and pressure. You will be lucky if you get half the rated output. SO buy one that is considerably bigger than you think you will need. You won't find they cost that much more and you will be much happier not spending all day trying to fill your water jug. It will also give you lots of room to grow later and not have to buy another unit. Particularly since you are talking about a bog which will take ALOT of water.

Post filtering for watering plants, drinking etc is utterly rediculous and a waste of money. The RO water is 98% pure or better. Unless you are running a reef aquarium or some sort of scientific lab there is no need to post filter with carbon or DI.

Any decent hardware store will have brass adapters to fit your sink and the typical garden hose connector you get with most units so hooking to your sink should not be a problem with a little hunting around for the correct fittings.

Invest in a good TDS meter so you can periodically check your water quality

A good company will rate their carbon prefilter by how many gallons of TOTAL water can go through it. For example a 10,000 gallon carbon block. Will last however long it takes you put 10,000 gallons through it. You could replace it every 6 months or so but why if it takes you 12 to process 10,000gallons? It doesn't have to be exact... measure how many gallons of waste water for each gallong of RO water then just do an estimate on how many gallons of RO water you make each week and calculate it out.

Example. You use 5 gallons of RO water a week and it takes 4 gallons of water to make 1 gallon of RO water. That equals 20 gallons/week through the carbon filter. 10,000/20 = 500 weeks before it needs to be changed!
 
Joined
Aug 25, 2007
Messages
642
Location
San Diego, CA USA
Hey Mcantrell... I bought a couple off of Ebay a while ago and I love them. I use one for my greenhouse and one for inside the house. I believe I bought the one that Av8tor (butch) recommended to me. Here is a thread you may find useful... in it are some ebay links you may want to check out (the listings are expired, but the vendors should still be around). Hope this helps:

http://www.terraforums.com/forums/showthread.php?t=112605&highlight=looking+to+buy+RO+unit

Daniel
 
Joined
Dec 14, 2008
Messages
100
Look around some of the reef/marine aquarium forums and classifieds as well, as PetSmart recently had an online blunder, pricing one of the R/O units at $0.01 each, if I remember correctly. Plenty of people snagged the deal, buying several of them, and offering them up for sale at very low prices.
 
Joined
Dec 30, 2008
Messages
12
does the difference in pressure on the faucet vs the pipes matter much? It seems like the faucet would under preform or not even work with some filters.

Another question... Is there a particular type that should be used to connect to something like a faucet or water hose? Could just any unit be used if an adapter is made out of stuff from the hardware store to connect to a water hose or faucet?
 
Joined
Oct 12, 2001
Messages
4,641
Location
Far Away NY
It will depend somewhat on the faucet. First thing is to unscrew the aerator from the faucet and bring that with you to the hardware store to match the one side. Kitchen faucets usually have threads on the outside so you will need a female fitting. Bathroom faucets usually have the threads on the inside so you will need a male fitting. They make fittings that will go from either faucet to a female hose fitting. They are usuually in the brass fittings/adapters in the plumbing section.

All the RO units I have seen have a female hose fitting on the water input tube. You could use this or remove it and get another fitting that will slip into the tubing on the unit. There are alot of options for the unit side. It depends what kind of adapter you find for the faucet side.

Once you remove the aerator there will be plenty of water flow through the faucet so as not to impede operation of the unit from insufficient water flow. The limiting factors at that point become line water pressure and less so temperature since you can feed a little from the warm water side if you don't mind paying to heat up your water before dumping 3/4 of it down the drain.
 
Joined
Dec 30, 2008
Messages
12
Another question. If i got a unit that could run off of a water hose and use it outside, would the waste water be much worse than tap? If i collected the waste water from it into a bucket or something would i be able to water the same things i use tap water on?

Thanks. This is a great thread... just in time too. :)
 
Joined
Dec 30, 2008
Messages
12
Thanks. I appreciate the help you all have given so far. I have a few more questions.

1) After a lot of research, I'm thinking this is just easier and probably cheaper in general to put under your sink with a saddle valve. I have read many recommendations around the forum for pumps to raise the pressure of the RO system. Most of the directions I could find with google didn't really get into pumps. So why the recommendation to get a complete system with a pump up front? Is this more of a just in case type of thing or is it something that would improve the operation of the unit regardless of initial line pressure?

2) Im unclear how the units stop running. Is this purely based on pressure inside the storage tank and water pressure or is this an electrical switch? Does the storage tank require power for pressure or is this achieved from the line pressure?

3) Regarding the recommendation for a higher GPD than you expect to use. If there is a 2 or 3 gallon storage tank, is this as much of a concern? I understand the price difference between a 50 gpd and a 100 gpd is relatively small... but if I find a good deal on a lesser model is it likely I would even notice a difference at the tap? I dont imagine i would exceed 20 gallons per week but i never really thought about what my water use is for cooking/drinking.

4) And lastly, my sink has 2 drains... left and right. The left one has a garbage disposal connected and the right side has the dishwasher. Where would be best to connect the drain line? Bear in mind im about to replace the disposal and the trap kit with new parts... so reconfiguring a bit isn't a problem.
 
Joined
Jan 19, 2007
Messages
4,832
Abc,

There are two different pumps really, a permeate and a booster...

RO systems are highly dependent on line pressure, so if you have low line pressure then you will have to use a booster pump or the system will not work properly (somewhat common) or not at all if the line pressure is excessively low (rare).

Ideal = 60psig, anything below 45psig will start causing problems with 50 being the recommended minimum and 80 the recommended max (typical)

Lower pressure = lower efficiency, lower rejection ratio, increased recovery time, increased brine ratio, decreased prefilter and membrane life

Normally if someone is having repeated issues with their RO system, this is the root cause.

However, if the pressure is fine, then its not needed unless you just want to tweek the system for max performance

Permeate pumps are the other hand are primarily used to overcome the decrease in pressure differentail across the membrane and the jump in brine rate as the holding tank fills. This wastes water, lowers membrane efficiency, increases recovery time and decreases prefilter life.

pp100_anlage.gif


(notice that the membrane outlet pressure remains a constant 5psig regardless of tank pressure)

Permeate pumps while not required, are a very nice upgrade. They can really increases filter life and rejection ratio on captive tank systems. Usually anyone who has installed one will tell you they love it.... plus they just sound kewl LOL

(They can also help with low line pressure issues, but this is not their designed purpose)

So when you research pumps be sure you are comparing apples to apples mate ;)

#2 = if it is a captive air tank (accumulator) type system, the system is shut off buy a hydraulically operated auto shut off valve. It will shut off the inlet flow when the output pressure is approx 60% of inlet pressure. If you upgrade with a permeate pump, you can swap this out for a 90% ASO valve (auto shut off) or no ASO valve at all since the tank pressure is now isolated from the membrane outlet. (maximum membrane pressure differential is maintained regardless of tank pressure (the permeate pump isolates the membrane outlet and "pumps" the permeate into the tank.)

#3 The gpd rating is of the membrane with "ideal" pressure diff and water temp. This is not a "real world" value to begin with, plus the larger system will give you faster recovery times. Normally its also easier and cheaper to find the 100gpd membranes when you need a replacement.

Membrane Output Calculation
Membranes produce the rated gallons per day (GPD) at 60 psi (4.1 bars) operating
pressure, 77°F (25°C) operating temperature and 500 ppm total dissolved
solids.
Membrane output gallons per day (GPD) depends on operating pressure, water
temperature and the ppm TDS in the feed water.
Expected GPD = Rated GPD × PCF × TCF
PCF is the pressure correction factor
TCF is the temperature correction factor
Calculation of Pressure Correction Factor (PCF): The output (GPD) from
the membrane is directly proportional to the applied pressure.
Note: The membrane is rated to produce the rated GPD at 60 psi. For any pressure
other than 60 psi the output GPD is multipled by the PCF.
PCF = Line Pressure (in psi) ÷ 60
Calculation of Temperature Correction Factor (TCF): The output (GPD)
also decreases with decrease in temperature. This is because water viscosity
increases with decrease in water temperature.
Temperature Correction Factor Table (TCF)
°F /°C TCF °F \°C TCF °F \°C TCF
41.0 /5 0.521 59.0 /15 0.730 77.0 /25 1.000
42.8 /6 0.540 60.8 /16 0.754 78.8 /26 1.031
44.6 /7 0.560 62.6 /17 0.779 80.6 /27 1.063
46.4 /8 0.578 64.4 /18 0.804 82.4 /28 1.094
48.2 /9 0.598 66.2 /19 0.830 84.2 /29 1.127
50.0 /10 0.620 68.0 /20 0.857 86.0 /30 1.161
51.8 /11 0.640 69.8 /21 0.884 87.8 /31 1.196
53.6 /12 0.661 71.6 /22 0.912 89.6 /32 1.232
55.4 /13 0.684 73.4 /23 0.941 91.4 /33 1.267
57.2/14 0.707 75.2 /24 0.970 93.2 /34 1.304
SpectraPure ®
SpectraPure®Inc. Fax 480.894.6109 Fax us toll-free 1.877.527.7873
E-mail: spectra@spectrapure.com Visit us on the web www.spectrapure.com 13
Production Rate
Membrane Output Calculation Example
What is the expected GPD from a 75 GPD System at 40 psi pressure and 60°F
water temperature?
PCF = 40 ÷ 60 = 0.666
TCF = 0.754 (from Table 1)
Expected GPD = 75 × 0.666 × 0.754 = 37.7 GPD ± 15%



#4 as long as the drain will not experience any type of "back" pressure from the plumbing and maintains some type of suction break.,

Av
 
Joined
Dec 20, 2007
Messages
572
Location
Chino Hills, CA, USA
I got my system on ebay too. Payd like 80$ for a "0 ppm" unit. I don't get a 0 ppm ....i get around 10 ppm wich is more than fine by my standards...no tank on mine but i do suggest to get one. It's a 5 stage filter unit.
 
Joined
Dec 30, 2008
Messages
12
Thanks for you replies. I think i got what i need to move forward with my RO system. Now to wait for payday.....
 
Joined
Nov 29, 2008
Messages
497
Location
Twin Falls, ID, USA
Got my TDS tester a few days ago. 350+ TDS in my tap water. Yeow. RO Filter is the way to go, I guess, but given the hard water stains everywhere, that was kinda obvious. :D


So for home use, it doesn't matter too much as long as I get a carbon prefilter? And ... maybe a pump? How do I test my water pressure?
 
Joined
Mar 10, 2008
Messages
475
Location
Austin, TX
i got a 100gpd model from purewaterclub.com for about $88 at the time without the tank a while back and it produces 10ppm though its the 0ppm filter with the dual DI....if i replace the canisters it might do 0ppm, they list on ebay as well.
 
Joined
Nov 29, 2008
Messages
497
Location
Twin Falls, ID, USA
Is there an easy way to test my faucet to see if I'd need a pump? Thinking of making the splurge now that I have some extra cash and more plants, but don't want to overspend...
 
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