RO/DI slow flow

[bromion]

I'm sure this has come up, but I can't find it. I hooked up a RO/DI unit today, and everything appears to be set right, but my flow rate of RO/DI water is extremely slow. It's a 100GPD unit and so far it's producing 1 quart per hour as opposed to the 4 gal/hour it should.

I've flushed the RO membrane and checked all the connections. Any insights? Does it take time to get going? If so, how much?

Thanks!
Jason

 

[old salty]

What type of unit is this? Sounds like mine before I read the instructions where it said to close the valves. Make sure your RO flush valve is closed.

 

[bromion]

Yes, the RO flush valve is closed.

It's one of these:
http://cgi.ebay.com/New-Reef-6-st-1...itemZ4446164926QQcategoryZ20684QQcmdZViewItem

 

[jdieck]

Low water temperature and low tap pressure reduce the production significantly but not as much as you describe.
As mentioned above check that your flush valve is open and that the flow restrictor is also installed properly. With the flush valve closed the waste water volume shall be between 4 to 5 times the product water volume. Use a measuring cup and a stop watch to measure the volume ratios. If it is more than 4 to 5 times the restrictor is not properly installed or is not sized properly.
Some units do not have a fixed flow restrictor but one valve like that can be adjusted. If your unit has one of those try to adjust it to the above ratio. The restrictor shall be installed in parallel to the flush valve.

 

[bromion]

This unit has a restrictor built into the flush valve (assuming our terminology is the same). This part comes off one of two RO membrane outputs -- the one that drains to the sink. When the flush valve is closed (meaning less water flows to the drain), it's producing well over 10x the amount of waste water per RO water.

I will investigate the restrictor.

 

[jdieck]

The flush valve may be installed backwards. Does it has an arrow in the body indicating the flow direction?

 

[bromion]

Yes, it's pointed according to the arrow indicating flow direction. I supposed I could try to install it the other way, in case it's mislabeled.

 

[jdieck]

<a href=showthread.php?s=&postid=6974077#post6974077 target=_blank>Originally posted</a> by bromion
Yes, it's pointed according to the arrow indicating flow direction. I supposed I could try to install it the other way, in case it's mislabeled.

I do not think it is but nothing is lost by trying. I assume you close the valve completely.
In any case those restrictor/valve are usually rated for three sizes, 50, 75 and 100 gph systems. You may have to talk to the manufacturer for a replacment of the proper size.
Ideally you may watn an adjustable flow restrictor so you can set it to the pressure/temperature of your system.

 

[bromion]

I did a measurement and found that the system produces 1/8 cup for every 3 cups of waste water. That's 1:24. Also, the TDS of the DI water is in the 70s, which is even more disturbing. I am going to let it run overnight and see how it looks in the morning.

 

[jdieck]

<a href=showthread.php?s=&postid=6974433#post6974433 target=_blank>Originally posted</a> by bromion
I did a measurement and found that the system produces 1/8 cup for every 3 cups of waste water. That's 1:24. Also, the TDS of the DI water is in the 70s, which is even more disturbing. I am going to let it run overnight and see how it looks in the morning.

That is not right, it shall start producing 0 TDS after about 1 gallon even if the restrictor is not properly sized.. I have the feeling that either the lines into and out of the membrane may be switched or there is a leak in the packing around the membrane cartridge inside the housing.

 

[uscgbeachbum]

I also have a weak RO/DI output. I get about 1/2 gallon per hour. I've tried everything. Apparently, most homes don't have enough pressure. I'm going to a booster pump which you can find on airwaterice.com or elsewhere.

 

[AZDesertRat]

What you are experiencing is exactly why I only recommend units which use a Dow Filmtec 75 GPD true RO membrane. Other brands of membranes require 60 and even 65 psi to produce their rated GPD while Dow Filmtec and only Dow is rated at 50 psi. All membranes regardless of brand are rated at 77 degrees F so water colder than that or with less pressure than what it is rated at will greatly reduce the output. A higher waste flow is also common with cold water so what you are seeing coule be normal.
If it were me I would return the unit you purchased and buy a Typhoon III from www.airwaterice.com . RO/DI is not a place to skimp on quality and as I have said hundreds of times " You get waht you pay for with RO/DI units". In this case cheaper is not better and will end up costing you much more in a very short time due to inefficiency and short DI life.

 

[bromion]

<a href=showthread.php?s=&postid=6974974#post6974974 target=_blank>Originally posted</a> by uscgbeachbum
I also have a weak RO/DI output. I get about 1/2 gallon per hour. I've tried everything. Apparently, most homes don't have enough pressure. I'm going to a booster pump which you can find on airwaterice.com or elsewhere.

My temp is 60 degrees F, measured in the morning so that's as cold as it's going to get. I'll see what I can find for a pressure gague.

Incoming TDS is about 210ppm, which is well below the problem area for this filter, far as I know (manual says at 800ppm you need greater than 40 psi incoming).

 

[jdieck]

Bromion:
You can inspect the inside of the membrane housing by unthreading it's cap and pulling the membrane out. Let me know if the instructions do not include how to do it, I think I can get some info for you.
Also as a test (and test only) try installing a John Guest valve in the waste line and adjust it as a restrictor to say 5 waste for 1 of product, if it is possible to adjust then the inners of the membrane are OK and you need a new restrictor, Do not restrict it below 4:1

 

[bromion]

<a href=showthread.php?s=&postid=6976617#post6976617 target=_blank>Originally posted</a> by jdieck
Bromion:
You can inspect the inside of the membrane housing by unthreading it's cap and pulling the membrane out. Let me know if the instructions do not include how to do it, I think I can get some info for you.

I have opened the RO membrane housing and looked at it. What should I be looking for?

 

[jdieck]

<a href=showthread.php?s=&postid=6977262#post6977262 target=_blank>Originally posted</a> by bromion
I have opened the RO membrane housing and looked at it. What should I be looking for?

If you can pull the membrane cartridge out check that the large seal around the cartridge is not damaged, also check that the "O" ring at the end of the cartridge is also in good condition. If everthing looks OK just assembly it back and try the valve in the waste line test.

 

[bromion]

I looked up some info on flow restrictors, and it seems this may have the wrong one. It has something labeled "Flow-450" which I assume means 450ml/min. Web sites I've seen have 800-1000 ml/min restrictors for 100 GPD membranes. Hopefully I can get a free replacement on this part.

 

[bromion]

I tested the restrictor and confirmed it's 450 ml/min. I can set it so that it's about 1000 ml/min, in which case I get a 20:1 ratio instead of 30:1. If I set it even slower I can get down to 15:1, but that's the best I've seen.

I did re-seat the RO membrane and the TDS coming from that is now 10ppm, at least.

 

[jdieck]

Seems like you will need further restriction to make it work properly but I am concerned. you should not need that much restriction unless you have a plugged membrane. Did you get the system new?

 

[bromion]

<a href=showthread.php?s=&postid=6978263#post6978263 target=_blank>Originally posted</a> by jdieck
Did you get the system new?

Unfortunately, no. I bought it from someone on the boards who said he hardly used it at all. I contacted the manufacturer to see what they recommend. Worst case I'll try to return it to the seller or have to buy a new RO membrane. Grr.