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#1
10/29/2007, 05:21 PM
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50 gpd TFC membrane
I need to replace my TFC membrane;prices start from 69 to 116 dollars, any sugestions ?
Mine is less than one year old. It is a coralife Pure-Flo II with booster pump. I am getting 9 to 1 waste water ratio. Called coralife; they said the membrane must be bad. I don't know too much about RO/DI units and could use your help. Thanks! |
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#4
10/29/2007, 07:39 PM
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A 75 GPD Dow Filmtec will fit as it is a standard size and should run you $45 or so. Get a matched flow restrictor or better yet a capillary tube type you trim for an exact 4:1 waste ratio or an adjustable one again so you can fine tune the waste flow.
http://www.thefilterguys.biz/ro_membranes.htm http://www.buckeyefieldsupply.com/sh...owspecials=153 http://www.purelyh2o.com/home.php?cat=261 |
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#6
10/29/2007, 10:39 PM
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With Kent you are paying for the name. If you want the best membrane get a hand tested Spectrapure Select series membrane which guarantees 98+% rejection rate, I am getting 99.23% with mine.
If you are looking at price as a selling point get the Dow 75 GPD since it will make water close to 100% faster than your 50 GPD. The GE Osmonics which yours probably is is rated at 50 GPD at 65 psi and about 35 GPD at 50 psi. The Dow is rated at 75 GPD at 50 psi and 90 GPD at 65 psi. |
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#10
10/30/2007, 12:48 PM
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The Dow 75 GPD is the same 96-98% efficiency as the GE Osmonics if not slightly better. Stay away from the Dow 100 GPD though as it is only 90% efficient.
A booster pump should be raising your pressure higher than 45 psi? What is it without the pump? As ATTR suggested, time the flows from both your good water and waste water lines as see what your waste ratio is. It should be close to 4:1, of 4 gallons of waste to 1 gallon of good. With a measuring cup or other graduated vessel and a watch you can get the info you need. If it is much higher than 4:1 you are losing pressure out the waste which is not allowing as much water to pass through the RO membrane. Coralife uses a capillary tube typr flow restrictor which can be found inside the waste line if you disconnect it, it will look like a piece of spaghetti with a larger piece on one end. Normally if they are the correct restrictor you trim the length to adjust the flow but if its the wrong one trimming it will not help as you would already be wasting too much. At 4:1 with a 75GPD membrane you should see very little pressure drop at all, heck I am producing 240 GPD at 4:1 waste and only see a few pounds pressure drop. |
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#11
10/30/2007, 05:48 PM
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Ratio is about 9:1,pressure going in to unit is about 35 to 40,I don't have a pressure gage on my RO unit so I can't tell what it is. I never got better than 25 gpd but now it is about 11 gpd, restrictor in my unit is like a 4 inch long white tube #420 and it is 3:1 ratio. I am going to take your advise and replace the membrane with a 75 gpd and change restrictor also but I need to find out the number for that.
Thanks a lot ! |
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#12
10/30/2007, 05:54 PM
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In the first sentence you say the ratio is 9:1 and later you say 3:1 ? If its 3:1 you are good if its 9:1 thats probably a big part of your pressure problem, its all going to waste and not through the membrane. Did you time each flow, good and waste for a minute or two and actually calculate your true waste ratio? You really need to do that. Your system and pressure may not be as bad as you think.
As a temporary fix or troubleshooting technique, install a 1/4" ball valve on the end of the waste line and squeeze it down until you get to 3 or 4:1 waste ratio and see how much your productiuon picks up by comparing the time it took to fill a measuring cup before and after the valve was installed. This will help you to determine if you really do have a problem or not. If it helps you may want to buy either an adjustable flow restrictor or the correct capillary tube type and trim it for an exact fit. |
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#13
10/30/2007, 06:48 PM
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3:1 is what resrictor is rated. I will try your troubleshooting technique. if I put a valve on waste water line and squeeze it down would't that make the water come out the RO end like if you close it all the way all the water will come out the other way or not?
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#14
10/31/2007, 06:00 AM
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Quote:
Russ
__________________
RO/DI equipment and supplies at www.BuckeyeFieldSupply.com Sales@BuckeyeFieldSupply.com |
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#15
10/31/2007, 06:08 PM
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AZDesertRat:
I did what you said, here it is. at full open 131/20 TDS 7 ratio 6.5:1 partly open 87/19 TDS 12 ratio 4.5:1 I was getting 9:1 ratio but I think after putting the membrane back in it changed to 6.5:1. let me know what you think. Thanks! |
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#16
10/31/2007, 06:19 PM
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Decipher your numbers for me. What do they represent? Is it at full open in a one minute time you got 131 ounces of waste and 20 ounces of good water at a final TDS of 7? Thats the kind of info we need. I am not sure what your numbers mean.
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#18
10/31/2007, 07:05 PM
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Seems strange that the production rate did not go up as you increased the backpressure and the TDS actually went up and not down?
Russ, you have any ideas? |
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#19
10/31/2007, 07:32 PM
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Well, when these odd sorts of things happen, theres a number of things that could be happening:
tds meter not calibrated tds meter not accurate tds measurements not taken carefully tds measurements affected by tds creep fluctuating pressure to the membrane may have broken some scale loose from inside the membrane 30 second measurement period too short and the list goes on... We still don't know how much pressure is reaching the membrane. At only 35 to 40 psi line pressure, who knows what's actually reaching the membrane. AZ is right - with higher pressure you should see higher rejection (lower tds in the RO water). Bottomline: If it were my system I'd get a pressure gauge add on kit and a new flow restrictor. Two inexpensive mods that will likely have your system up and running quickly. Russ
__________________
RO/DI equipment and supplies at www.BuckeyeFieldSupply.com Sales@BuckeyeFieldSupply.com |
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#22
11/01/2007, 10:07 AM
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Mount it between the carbon block and the inlet to the RO membrane. Some RO housings have a plugged hole in the side already for a pressure gauge such as you see here on mine.
This gauge then reads the true pressure being seen by the membrane after any pressure drop through the filters. Notice I have two gauges, the one is on the incoming tap water line measuring house pressure, the other is the one on the membrane. This way I can see at a glance if I have a pressure drop or not. The problem with one gauge is unless you know what the house pressure is you don't know if you have a pressure drop. Not all water systems have constant pressure, they experience sags or spikes due to time of day usage, seasonal changes, pumps out of service etc. 
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#24
11/01/2007, 06:11 PM
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You'd want to place the DI after the RO membrane. The membrane is the workhorse of the system - think of DI as a polisher in this configuration.
Russ
__________________
RO/DI equipment and supplies at www.BuckeyeFieldSupply.com Sales@BuckeyeFieldSupply.com |
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#25
11/01/2007, 06:19 PM
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In my system, left to right it goes
1. 0.2 micron prefilter 2. 0.5 micron carbon block 3. RO membrane(s) as I have a piggyback system now with two. 4. 14 gallon pressure tank 5. Either back to the 3rd canister in line which is a MaxCap DI then the canister on the right which is a SilicaBuster DI or 6. To the drinking water faucet via an inline taste and odor cartridge. |
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Linear Mode
