Is my LFS taking me for a ride?

[bertoni]

The output of a 75 gpd membrane should be about 75 gpd, <b>if</b> the input pressure is perfect, which I think is about 75 psi. Otherwise, the output likely will drop as the pressure drops. Clogging will reduce it even more.

I wouldn't use tapwater in the tank. Even if the city water is clean, any copper pipes, etc, along the delivery path could cause a major problem. Also, cities have been know to treat the water with anti-corrosives from time to time.

 

[Daniel Reef]

I am concerned that the LFS is suggesting that you seek his advice before making online purchases so that he can instead convince you to buy his products. JMHO.

 

[tengquen]

I am concerned that the LFS is suggesting that you seek his advice before making online purchases so that he can instead convince you to buy his products. JMHO.

I'm tellin ya...I have no idea what to think of this guy. He seems so nice. At best he is actually an ro/di expert and is giving me sound advice. At worst he wants me to buy his ro/di unit and not get pis#ed when it only does 14 gallons in 24 hours. lol, sheesh.

 

[lordofthereef]

Here is the latest quote from my LFS...

We deal with the largest importer of ro products in the country, and they put this model together per my designs. I actually have designed a mini 100gpd RO unit too, and before Laura and I started the store we sold them on the net. I am an expert when it comes to ro/di and I can assure you that no 100 gallon per day membrane produces 100 gallons in a day. That is completely false and obviously the people are not versed in how they rate units. For a system that would produce that much in 24hrs would require a much larger membrane. In home models, 150-200 gallon per day membranes are about the largest that are available. A NEW 100 gallon per day membrane will produce about 3-4 gallons about every 2 hours, and of course this depends on the pressure of the incoming unit, the TDS of the tap water and the amount the filters have already absorbed. Water that comes out a unit like that is about the same flow rate as an IV drip. Your unit will produce faster when it is new, and output will decrease as the filters become more and more saturated. On average it is about a 4:1 ratio of waste to purified water.

Really, I am no expert with RO units, but as I said, mine is rated for 75gpd and I am able to get more out of it running at right around 70 psi. I am not sure if production is dependent on the TDS of the input (mine is about 250) but I can tell you that I far exceed what I "should" be getting based on what your LFS owner is telling you. I would think we would see a lot more literature and complaints along the lines of "why is my 75gpd unit only producing 10gpd of RO water?" if that were the case...

 

[lordofthereef]

# 50, 75 or 150 gallon per day GE/Osmonics (r) "Desal (tm)" TLC membrane modules - for fast production time and high removal rates: 30 minutes for one gallon at 98% purity for 50 gpm, 20 minutes for one gallon at 96% for 75 gpd, 10 minutes per gallon at 93% for 150 gpd (at 65 psi and 77º F). Recovery rate is a fixed 25% (1:4 product to waste ratio). NSF-58 certified.

This info is the closest I could find to an actual number online. As you can see, the values represented there are actual values (such as 30 min to make one gallon using a 50 gpd filter equates to a 48 gpd of actual clean RO water produced). It sounds to me like the owner is making claims that people are not educated about what gpd in an RO system truly means, but it may be he who is misinformed...

Again, I am no expert with RO systems, I only go with what I see and read in this case, but IME whatever the system is rated for is a value given to how much pure water will be produced, not how much water runs through the system per day.

 

[Daniel Reef]

Really, I am no expert with RO units, but as I said, mine is rated for 75gpd and I am able to get more out of it running at right around 70 psi. I am not sure if production is dependent on the TDS of the input (mine is about 250) but I can tell you that I far exceed what I "should" be getting based on what your LFS owner is telling you. I would think we would see a lot more literature and complaints along the lines of "why is my 75gpd unit only producing 10gpd of RO water?" if that were the case...

I agree with this comment which makes me question why the LFS is telling you this. Seems like he is vigorously pushing his "line" and, therefore, I would question not only this advice but other advice s/he has given the original poster.

 

[lordofthereef]

It is also worth noting that companies that work with RODI (my favorite is air water and ice, but there are many) are generally super great at answering questions via email. I would shoot them an e-mail and find out. Perhaps I will do that myself, since I am now intrigued. I would trust a company that sells only RODI products (like airwaterice.com) over an LFS owner.

 

[lordofthereef]

I just sent an email to air water and ice. I will respond to this post by copying and pasting their response. Here is my original email pasted:

Hello,
I am writing to clear up some possible misinformation I have received in deciding on an RO/DI unit for my reef. I was under the impression that gallons per day ratings (ie 50gpd, 75gpd, 150gpd) were based on how much actual RO water is produced. In the example of 50gpd unit I would have expected to see 50 gallons of RO water produced in a 24 hour period of time. I have since been told that the gallons per day rating has to do with how much water is actually processed in a day meaning that in a 50gpd filter I am processing 50 gallons in a 24 hour period. Assuming a 90% rejection rate this leaves me with only 5 gallons per day of clean 0TDS RO water. To me this doesn't seem right and was hoping to clear that up.

 

[tengquen]

I just sent an email to air water and ice. I will respond to this post by copying and pasting their response. Here is my original email pasted:

Hello,
I am writing to clear up some possible misinformation I have received in deciding on an RO/DI unit for my reef. I was under the impression that gallons per day ratings (ie 50gpd, 75gpd, 150gpd) were based on how much actual RO water is produced. In the example of 50gpd unit I would have expected to see 50 gallons of RO water produced in a 24 hour period of time. I have since been told that the gallons per day rating has to do with how much water is actually processed in a day meaning that in a 50gpd filter I am processing 50 gallons in a 24 hour period. Assuming a 90% rejection rate this leaves me with only 5 gallons per day of clean 0TDS RO water. To me this doesn't seem right and was hoping to clear that up.

Thanks for doing that. I am also waiting for a response from bulkreefsupply.com

 

[Daniel Reef]

I'm interested in buying a RODI and so I would like to hear what airwaterice.com says.

 

[SeedlessOne]

A 75gpd will produce 75gpd of clean RO water with correct water pressure and temps. Period.

The LFS "expert" is wrong.

 

[jayhawk317]

i use jugs of distilled water from walmart to fill my tank and do my water changes. i measured it on a tds meter and it came out to 2ppm, which isnt bad. its the jug with the purple caps.

 

[MBZ]

My Kent Marine Hi-S Maxxima 60 GPD RO/DI System @ 80psi produces 60gpd for me in the summer and around 50gpd in the winter.

Mark

 

[tengquen]

BulkReefSupply

BulkReefSupply

Here is their response to my ro/di question...

This is somewhat accurate but he is really overstating his point. If you operate within the specs it will produce the specified amounts of water. Especially when you are not dealing with the typical back pressure from a pressurized storage tank. In reef aquaria we general don't use tanks like that , we fill garbage cans or drums with water. If you have really cold water or low water pressure it would produce less. To be honest most people don't get too tied up in wither it does 75 or 60 GPD because in the end it is slow and you have to turn it on the day before you want water regardless. I am a certified water specialist , certified by the Water quality association http://wqa.org/ . We also build , sell and support a couple hundred RO systems a month. There is absolutely no way I would tell people that it is a 75 gallon per day unit if it was going to perform as poorly as the gentlemen has said below.



In this hobby you will find a lot of conflicting information and a lot of people have a lot of opinions, my best advice to you is to find someone you trust and listen to them. I don't agree with the gentlemen below and do not share his experiences but if you otherwise trust what he says and hasn't let you down he might be that person for you.



I have included a link to the spec sheet for the dow 75 gallon per day membrane we use(tw30-1812-75.)



Product Name
Permeate Flow Rate
gpd (m3/d)
Stabilized Salt Rejection
(%)
Minimum Salt Rejection
(%)

FILMTEC TW30-1812-75
75 (0.28)
98.0
96.0




1. Permeate flow and salt rejection based on the following test conditions: 250 ppm softened tapwater, 77°F (25°C), 50 psig (3.4 bar), and 15% recovery.
2. Permeate flow rates for individual elements may vary +/-20%.






http://www.dow.com/PublishedLiterat...seps/pdfs/noreg/609-09010.pdf&fromPage=GetDoc













Thank you,



Ryan Batcheller, President

Aquatic Sales Solutions & Bulk Reef Supply

Phone: 763.432.9691

 

[Daniel Reef]

Interesting response from BRS. But I guess my original position was accurate. It is better to ask the online supplier about their product than to ask someone else or a purported "expert."

 

[Buckeye Hydro]

Filmtec membranes are the most popular membranes used in this hobby, and are what you'll find in most RODI systems.

They are factory spec'ed re how much water they will produce given certain conditions. So a 75 gpd Filmtec membrane will produce 75 gallons in 24 hours (plus or minus 20%)with these conditions:
feedwater is 77 degrees
feedwater pressure is 50 psi
feedwater tds is 250 ppm
waste to purified water ratio is about 5.5:1
feedwater is softened

Nearly no one has 77 degree feedwater, and colder water means slower production.
Some folks don't have 50 psi, and lower pressure means lower production.

Have lower temperatures AND lower pressure? You'll get slower production yet.

For instance, here's what you might expect in three different situations from a 75 gpd Filmtec membrane where we vary only pressure and temperature from the factory spec's:

SITUATION 1 (@ Factory spec's)
Temp: 77 F
Pressure: 50 psi
Production: 75 gpd

SITUATION 2 (example winter conditions)
Temp: 58 F
Pressure: 50 psi
Production: 52 gpd

SITUATION 3 (example summer conditions)
Temp: 68 F
Pressure: 50 psi
Production: 63 gpd

Russ @
Buckeye Field Supply

 

[phil47952]

New Setup

New Setup

Tengquen,
Great thread, I've had RO/DI units for years but I learned a lot here, thank you

Phil :beer:

 

[Chiefsurfer]

Hey BuckeyeFS, i have a question regarding above. I have some very cold water her, and my water is roughly 45 degreesF, however my pressure is 80, MAYBE more. Does having higher pressure or boost production, or is anything over 50 unnecessary, and the temperature makes the difference?

 

[Buckeye Hydro]

Hey BuckeyeFS, i have a question regarding above. I have some very cold water her, and my water is roughly 45 degreesF, however my pressure is 80, MAYBE more. Does having higher pressure or boost production, or is anything over 50 unnecessary, and the temperature makes the difference?

Higher pressure can compensate for lower temperatures.

SITUATION 1 (your current)
Temp: 45 F
Pressure: 80 psi
Production: 67 gpd

SITUATION 2 (with a booster pump)
Temp: 45 F
Pressure: 90 psi
Production: 76 gpd

but because you already have realitively high pressure, and we don't recommend pressurizing residential scale systems over 90 psi, the benefit you'd get from adding a booster pump would not be very impressive.

Russ

 

[Chiefsurfer]

yeah, that helps a lot. I don't know my exact pressure, but I know it is very high. In my kitchen sink, a flat plate about 10" below my faucet on full pressure, can splash 3-4 ft down the counter. Good to know. This is probably why I get slightly more than my RODI unit is rated for.