Filtered water to waster water 1:100 !

[Runner]

I hooked up a used RO/DI unit last night. It has new filters and a new RO membrane. I wasted everything for two hours like I was supposed to, then started collecting the filtered water. I was also collecting the waste water in a 55 G trashcan. Over the course of 2 hours, I had to empty the trashcan twice and only produced 1 gallon of filtered water (at ~10 TDS). That is about a 100:1 ratio of waste to filtered. That is ridiculous.

Any ideas as to what I may have done wrong or what may be wrong? Perhaps the flow restrictor on the waste water has given out?

Also, any info that describes in detail how a typical RO unit functions would be help me understand for myself what is happening here...

 

[BLockamon]

It sounds like either 1) your RO membrane isn't seated correctly and water is bypassing it (straight to waste) or 2) the inlet water pressure isn't high enough to push water through the membrane. Assuming you have the standard 40-60 psi water pressure, I'd start with #1. Try removing and re-seating the membrane.

 

[Angela Short]

If the water comming in is real cold it can also reduce the ro output but that is crazy. Do you know what your water pressure is off the tap you are using? Could also be the flow restricter like you stated but I would definetly check the PSI on your tap 1st. Good luck.

 

[jdieck]

1) Check that the output check valve if you have one is not installed backwards.
2) Check you have pressure above 40 psi
3) Check that the membrane is properly seated in the housing and there are no leaks around the outer seals of the cartridge
4) Check that the restrictor is properly seated and it is for the intended membrane, if you switched to a different membrane capacity the restrictor should have been replaced also or re adjusted to the new capacity
5) Check that your ASOV valve if you have one is operating properly

In that order

Good Luck!

 

[Runner]

Thanks for the help. Let me see here...

My water is cold, but not that cold. It gets much warmer in the summer.

1. There is no check valve on my output -- just dripping into an open container.

2. My water is 50~55 PSI coming into the house (and the RO unit is about 20 feet away on 3/4" pipe).

3. I'll try to re-seat the membrane when I get home. Is there proper method? I just pushed it in until it stopped. The fit seemed very tight.

4. Is the restrictor the thing that is labelled with 4.5 or 5.0 with a flow direction and installed on the waste line? If so, I see something that I did not do. I did not re-install the new capacity restrictor -- I just left the old one in. The old one said 4.5 while the new one said 5.0.

5. I have yet to test the automatic shut-off valve. I just let everything run last night.


I'll try all this tonight when I get home from work. Thanks!

 

[jdieck]

<a href=showthread.php?s=&postid=7074340#post7074340 target=_blank>Originally posted</a> by Runner
Thanks for the help. Let me see here...

4. Is the restrictor the thing that is labelled with 4.5 or 5.0 with a flow direction and installed on the waste line? If so, I see something that I did not do. I did not re-install the new capacity restrictor -- I just left the old one in. The old one said 4.5 while the new one said 5.0.

Yes that is a restrictor and has to be replaced if you got it with the new membrane. I do not remember well but by the numbering code it might be an autoflush restrictor. If it has a little handle like valve that is an autobackflush restrictor, if you open the handle it will bypass the restrictor to backflush clean the membrane for two minutes after each use and there will be no restriction, for normal pure water production operation the handle must be in the closed position (90 degrees to the water line).

 

[Runner]

<a href=showthread.php?s=&postid=7074389#post7074389 target=_blank>Originally posted</a> by jdieck
Yes that is a restrictor and has to be replaced if you got it with the new membrane. I do not remember well but by the numbering code it might be an autoflush restrictor. If it has a little handle like valve that is an autobackflush restrictor, if you open the handle it will bypass the restrictor to backflush clean the membrane for two minutes after each use and there will be no restriction, for normal pure water production operation the handle must be in the closed position (90 degrees to the water line).

That sounds like my problem. It has a little handle and I've been running it in the open position constantly. I thougth it was a shut-off valve. I'll give that a try first when I get home. Thank you very much.

I usually read up on stuff before I try to put it together. Trial by fire isn't pretty at times...

 

[jdieck]

<a href=showthread.php?s=&postid=7074412#post7074412 target=_blank>Originally posted</a> by Runner
That sounds like my problem. It has a little handle and I've been running it in the open position constantly. I thougth it was a shut-off valve. I'll give that a try first when I get home. Thank you very much.

I usually read up on stuff before I try to put it together. Trial by fire isn't pretty at times...

Just before trying install the new restrictor.

 

[RCS]

I would vote for the quick-flush valve as well. Most newer RO units have them and they need to be closed to make the proper backpressure on the system. There's no way you should be running through 100g+ in 2 hours.

 

[landragon]

I hope your solution works, which I'm sure it will. I run a booster pump and have a dialable flow restrictor. I dial it to 87psi back pressure at the membrane. I make 2.5g waste per 1g pure.

 

[Runner]

Heh. I hope it works too. I wasn't worried about 10:1 ratio because I plan to use the waste to water my grass or fill up my pool. A 100:1 ratio is downright silly...

 

[jdieck]

<a href=showthread.php?s=&postid=7075822#post7075822 target=_blank>Originally posted</a> by Runner
Heh. I hope it works too. I wasn't worried about 10:1 ratio because I plan to use the waste to water my grass or fill up my pool. A 100:1 ratio is downright silly...

The right ration is 4:1 to 5:1 higher than that you waste much water, lower than that and the rejection of the membrane drops meaning more impurities at the output of the membrane shortening the life of the DI cartridges.

 

[Runner]

Looks like the unit was in backflush the whole time. The flow is less on the waste now -- less than 10:1 waste-to-water ratio. I think I'll still toss the first 5G jug and then start using it.

Thanks for the help!

Now I just need to get a waste line long enough to route from my garage to my swimming pool...

 

[landragon]

Runner, depending on your incoming tds, I would think twice about putting RO brine into the pool on a regular basis. If the source tds are high, the brine will be concentrated even further. This could bring tds and hardness in the pool to levels not desirable that may result in stainig. My last job (6 years) was with bigger bodies of water and fish that complained when their tank was dirty

 

[jdieck]

IMO the concentration of dissolved solids will be irrelevant for pool purposes.
Here is why I think so.
Assuming a high 500 ppm TDS in the incoming water and a membrane rejection rate of 95% with a waste to product ratio of 5:1 the TDS in the membrane product output will be 25 ppm and in the waste water will be 595 ppm so a change from 500 to 595 mostly carbonates in the waste.
If we consider a high 20% water change per week for a 75 gal tank that will be 75 gals of waste water generated per week of 595 ppm which added to a 10,000 gal pool at 500 ppm makes for an increase to 500.7 ppm or 0.0014%. For comparison a 3% per week evaporation of the pool water will increase the ppm from 500 to 515.5 ppm. (500 / (1-0.03) = 515.5)
So in summary the effect of adding the waste water to a 10,000 gal pool will be 22 times smaller than the pool's natural evaporation (15.5 / 0.7). I would not be worried at all.
A smaller pool? Say 5,000 gal the increase will be 1.4 ppm still not a difference IMO.

By the way, in order to reduce my waste water in half I use a second membrane to process the waste water from the first membrane. That doubles my production of water for the same volume of waste with only and increase of 1.2 ppm in my product water which the DI cartridges are well capable of handling.

 

[Runner]

I have 160 TDS coming in. I don't think the slight increase will hurt my pool. Heck, I don't even think the wastes will keep up with evaporation.

 

[landragon]

I still think it would be better served on your lawn.