RO/DI production rate - what am I doing wrong?

ACBlinky

ACBlinky

Premium Member
I bought a 100gpd six-stage RO/DI, it didn't really come with instructions. A friend sent me a diagram, but it was still like working in the dark. I'm sure it's all hooked up correctly, but... maybe I'm wrong. I keep reading posts where people mention that it takes a certain amount of time to produce their RO water, and I get the feeling I'm doing something incorrectly with my unit, because mine produces water so much more slowly.
The unit is rated at 100gpd, and I find I get about a gallon an hour or so - I assume the other ~75g of the 100 are waste water, as the drain line seems to produce roughly three times as much water. The TDS of our tap water measures 144, and the water I collect measures 1. The waste water measures 167. The drain line steadily pours, whereas the filtered water coming out of the white line drips. Normal, or am I missing something here?

Here are some pics, not sure if this helps at all:

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Thanks for any help :)
 
its hooked up right. (i use an Aqua Safe unit) do you have any idea what your input water pressure is? is it possible that you put the RO membrane in backwards? you should be getting about 4 gallons per hour output.
 
1 gallon per hour certainly doesn't sound right. I've never actually measured, but I'm pretty sure my 50 gpd produces more than that. Simple math says that you should be getting around 4x that. Anyway, low water pressure could certainly be it. The input into mine is around 80 psi. Another thing it could be that got me is if you have a flush valve, make sure it's in the correct position. If it's open, you will get significantly less flow. Of course, you'll be getting much more than 3:1 waste water to purified water in that case as well.
 
Did you bypass your DI and flush the RO when you first started it... have to rinse out the preservative that the RO membrane has on it when new..

Try disconnecting your RO out-- and see what your production does... let it flush for a while.....if the flow is higher then your DI or that other filter after the DI are clogged up... you probably will need to replace one or both of them...

You can disconnect after the DI to see if its the DI or the thing after it restricting your flow..
 
They speed up as they get older. Also make sure your output destination is lower than your filter: they don't push uphill well.
 
Yes, the waste water coming out sounds low. Your water temp can make RO production slower -- but that would translate into even more wasted. Your input pressure would be important.

I do have a question regarding your setup -- what are the first three chambers you are filtering through before the RO? If you are filtering through the smaller filters first, you could be clogging things up and letting less water through. My RO/DI has the filters go from 10 microns, to 5 microns, to 1 micron (I think). If you have this reversed at all, then you may have clogged your smaller filter...

Jack
 
Wow, thanks for all the responses!
To answer some of the questions...

The output is lower than the filter, it's a bucket on the floor and the filter is on the counter.

The flush valve is closed

The filter is pretty new (<1 month), good to know they speed up as they age!

The RO membrane was already inside when I purchased the unit. There's only one way it fits AFAIK, and I haven't removed it - I did open the unit to ensure it was inside, but that's it.

I did flush the unit when I started it up; the instructions weren't clear, but that part of them was.

The first three chambers are micron filters and charcoal I believe. Thankfully, there are arrows indicating flow direction on the unit, so I'm pretty sure it's the right way 'round. Then the water hits the RO membrane, then the DI, and I think the last one is some more fine carbon.

The one thing I'm not sure of is the water pressure. I'm using a faucet hookup, as we can't mess around with the plumbing (we live in an apartment). I'm not sure how to measure it correctly with this setup... I just took the input line off the filter, attached it to the PSI meter and it seems to measure 30 - that's absurdly low isn't it? We're pretty high up in our apartment building, but never notice low pressure in the shower or anything. Maybe I'm not measuring it correctly, but then again maybe this is why the output is low!
 
Mine flows the other way (largest filter is on the right). Do the arrows tell you which filter comes next, or which direction the water flows through an individual filter?

Also, unrelated to flow, but related to the water quality -- It looks like you have a "taste" filter after the DI. I think this reintroduces stuff to the water to make it "taste" better. You might want to take that off the system and just use the water coming out of the DI for your tank.

Jack
 
Three things affect RO output. Pressure, temperature and incoming TDS.
You have answered two of the three already with the 30 psi and 144 TDS. The third, temperature can have just as great an effect on output as pressure.
If you look at the graphs here you will see that what you are experiencing is probably due to the pressure and temperature combination.

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

At 30 psi you will be at 40 GPD or so and combine that with a temperature of less than 77 degrees and you are probably close to what you are seeing.
Also your unit does not use a Dow Filmtec RO membrane which is designed to operate efficiently at 50 psi, it contains an Applied Membrane which is designed to operate at 60 to 65 psi. I try to stter people away from anything but genuine Dow Filmtec 75 GPD membranes for just that reason.
 
Hmmm... I was under the impression that only cold water should be used, I actually read that mixing in hot water will ruin an RO membrane! I did read posts about the differences between membranes (after I bought my unit) and will definitely switch when it comes time to change this one.

Crumbletop - as far as I know the bottom three are in the correct order. They were all pre-filled when they arrived, and the three are connected into one solid unit; one side says 'in', the other says 'out' so there's really no way to hook it up backwards.

Thank you all for the information, looks like the low pressure and a less than fabulous membrane are primarily to blame. I'll just keep being patient and slooowly filling my buckets. Good thing I don't have to do water changes on a 300g tank! :)
 
<a href=showthread.php?s=&postid=7328841#post7328841 target=_blank>Originally posted</a> by ACBlinky
Hmmm... I was under the impression that only cold water should be used, I actually read that mixing in hot water will ruin an RO membrane!
Click to expand...

theres a difference between hot water and ideal temp of 60Ã"šÃ‚º-70Ã"šÃ‚ºF. i think your main problem is low water pressure. did you get the unit used? if it was new didnt you get a pressure gauge with it?
 
You can get a pressure gauge for $10 at Home Depot. My RO runs 100gpd if you have 60psi pressure. However, our house is set at 40psi and there is nothing we can really do about it :( It seems like ours runs painfully slow too! We just started up my 90 gallon and it took about 3 days to make the water. It sounds like your unit is doing it's job and the water ratio is correct, so it's probably a pressure issue.
 
70 to 90 degrees is best with 77 being ideal. Less will produce less and more up to maybe 110 will produce more. Any hotter could damage the membrane and its almost impossible to try and manually temper the water temperature due to the low flow rate a RO produces.
 
Paintbug & Amy - I got the filter brand new off eBay, it's less than a month old.
I did get a PSI meter with the unit... that's how I found out my pressure is very low, around 30psi. Thanks for the temperature info, I had no idea!

Purelyh2o - I'm not certain what DI resin is supposed to look like as this is my first filter, but it's green and white. Some bits of it are brownish now, I assume it's changing colour as it becomes used up. When I opened the package to place the resin into the unit, I found it to be some of the strangest feeling stuff - it feels a bit slick and slimy, like tiny plastic beads coated in something oily.
 
AZ

AZ

Seriously have you ever seen anything like that?

It really is strange, not like anything I have ever used..

Look at the build up on the bottom..

2 cents?
 
ACBlinky

ACBlinky

It should be tiny plastic beads but what is getting me is the behavior of the resin and the overall apearance. Shouldnt be oily either but the sticky feel could just be the magnetic behavior resin tends to have to skin. I would love to get my hands on some of that just to see what the deal is with that.
 
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