Some real world TDS numbers..

[jackdp]

I've hooked up my new RO/DI in our new house. Water supply is well water with a pretty decent pressure (haven't measured yet). Before RO I get a TDS of around 425-450ppm. After RO I get around 100pppm TDS and after DI..I get 0ppm TDS. My concern is I wanted the RO portion (which we drink from) to knock the nitrates out of the tapwater. We live in a high farming area and our well water has nitrates that are off the scale of my Seachem nitrate test kit. After the RO filter the nitrates test around 10ppm or so. Does anyone have any real world figures along these same lines? Just curious if these results are too be expected. TIA

 

[steve-s]

Increasing the water pressure to an optimum level will also increase the rejection rate. You will definately need to test that but this would be the best place to start. It will more often than not reduce the total TDS out of the RO. An <<RO pump>> will easily fix that albeit put a decent dent in your wallent. Minimum 35 but preferabley 60-70 psi for best performance.


With such a high TDS going in, you will also need to ensure the prefilters/carbon are changed quite regularly, more than recommended. If they become exhausted, chloramines (if present) will make it though and the ammonia will destroy the RO membrane. You will also want to change the DI quite regularly.

Cheers
Steve

 

[jackdp]

Well, I had the system built with a permeate pump per the sellers recommendations based on having a well pump system. If I'm correct this uses the waste water to force permeate through the membrane and thus can help compensate for low incomng pressure. If I'm not correct then someone plz correct me..thx. It doesn't seem that my TDS numbers are off from what I've read in some other posts, its just that I wanted more nitrate removal from the membrane, but I do understand the input PSI issue. thx.

 

[saltwatersmac]

I just hooked up a new RO/DI. I am also on well water.

TDS #'s
before unit 420 ppm
after RO 19 ppm
after DI 0 ppm

Haven't checked nitrates with the new unit but will check later.

 

[jackdp]

saltwatersmac....do you know your water pressure in that set-up? I've tried everything and still get post RO TDS of 85ppm and my DI TDS is 4ppm. The place I ordered it from is very helpful and has already offered advice and to replace the membrane/whole unit if needed. I'm totally new to this well stuff and don't know how to find out my water pressure let alone adjust it. I have a pump in my basement with a psi gauge that turns the pump on at 40psi and off at 60psi hooked up to a small pressure tank. That's about all I know...

 

[saltwatersmac]

The unit I got from Buckeye Field Supply has a built in pressure gauge that reads after the sediment filter. I have the entire house on a filter system that goes like this 5-micron sediment filter, 2-micron carbon block, big Kenmore water softener and then on to the RO/DI. The water pressure varies from around 32-34 psi until the well pump cuts on and then it shoots up to about 52 psi. I would like to do something to keep the pressure on the unit to around 50 psi stable. The pressure you have the pump set at seems pretty standard for a well as far as I know. I have thought of adjusting the sets on the pressure switch at the tank but I need to check with my plumber first to see if it will cause a problem with the pipes.

Just a thought...have you checked to be sure the membrane is seated correctly in the housing? If the o-ring is rolled some it would cause some waste water to go through. Also it may depend on the kind of membrane you have. My unit has the Filmtec 75 gpd. I chose it over the 100 gpd because it is suppose to be about 98% efficient. With 420 ppm going in and 19 ppm going out, thats about 95.5%. I could probably get to 98% with higher stable water pressure. Yours is only around 75%, I would say something is wrong with the membrane.

HTH
Stephen

 

[seaham358]

I have my unit on a well also and I have the well pump set like yours, on at 40 off at 60psi. This gives my ro/di a low pressure of 30 and a high of 50.
My tap water only has a TDS of 180ish and after the membrane I was getting around a 8-9 TDS and 0 after the Dual DI's. All my filters are only 4 months old, when they get older I get a higher TDS out of the membrane
I got a booster pump and I now run a 2-3 out of the membrane with a pressure of 80 psi all the time.
I got a good deal on ebay for the 8800 booster pump and I love it......

 

[jackdp]

airwaterice.com is sending me a new membrane. So hopefully that will fix this issue. I did try removing the membrane and reseating it with no better results. I also fast flushed the membrane per the sellers recommendation to see if any dirt had clogged the drain or something with no avail. I do get low pressure here, I think it drops to around 28-30psi before the pump kicks in and then rises back to around 50psi or so. Still, my unit is equipped with a permeate pump which supposedly lets the RO stay efficient to as low as 30psi. even without the pump I would hope for better results. I'll wait for the new membrane and then see. Thaknks.

 

[seaham358]

AWI they are always willing to help out, their customer service is #1.

 

[saltwatersmac]

Sounds good Brad. Post back when you try the new membrane and lets see the results.

 

[MT79]

FWIW a good, properly functioning RO membrane should decrease the TDS by ten fold. For example, 300 TDS from the tap should be down to 30 TDS (or less) after the RO stage.
Good luck w/ the new membrane jackdp.

 

[jackdp]

Well, I've gotten my new membrane and installed. Tapwater was 475ppm, RO is now 40ppm, DI is 2ppm dropping. I'm going to let the system go for a couple of days and see if flushing won't hopefully lower some more.
On a side note, I just want to say how impressed I am with the service from airwaterice.com . They sent me new membrane right away, and even now while my TDS has dropped, they are still telling me it should be lower and may send a whole new unit. They even respond to e-mails Sat nights and Sundays..very impressed.

 

[seaham358]

Is the TDS meter calibrated? just a thought.. They sell calibration fluid for the meters or if you know someone that has one you can compare readings on the same water.

 

[jackdp]

I might calibrate it sometime. In the meantime, the more the system runs the lower the TDS is getting. I think I just had to get the membrane completely flushed and get all the previous "bad" water out of the tank and system. At last check TDS of RO was down to 32ppm and my DI water is now at 0ppm again. Hopefully switching from RO store bought water to DI water will help with my hair algae and cyano problem.

 

[saltwatersmac]

Good to hear jackdp.

 

[jackdp]

Strange thing I notice. If my RO holding tank is empty, and I'm running water right through to the tap the TDS is around 30ppm. If the tank is full and and has been for a day or so, I get a TDS of up to 60ppm. Anybody else that uses a tank for drinking water ever have this? Perplexing....

 

[saltwatersmac]

I don't use a tank but if its plastic it can raise the TDS from what I've read.