TDS the same coming out as going in RO system?

[Monkeytank]

I have about 40 tds from my cold tap water. I've got it running through a a BRS RO/DI system with a new sediment filter, a 5 micron carbon block that's new, a 1 micron carbon block that's about a week old, and two new 100 gpd membranes. I let it run for 2 hours after putting in the two membranes, without going through the DI, then I hooked it up to my new three stage DI. I noticed the TDS going in to the first DI stage was 38, then zero, then zero, and the output water tests zero. I verified the TDS coming out of the RO part of the system is 40.

It's running at 45 PSI. I've got a booster pump coming this week to address that. Still it seems like the filters and membranes should reduce at least some TDS. I tried flushing the membranes but when I turned the lever, I noticed there was no decrease in the output water. I checked the black drain line and there was barely a dribble coming out. Even with the lower PSI, it seems like there should be more waste than RO output.

Basically I have all RO output and just about zero waste water. I get zero TDS water for the output, but there is just as much TDS coming out of three filters and two membranes before it goes through my DI, and I cant flush the membrane. Ic tould just be that I need more pressure, but still seems weird to me. Any ideas about what's going on?

 

[mtfish]

Only thing I can think of is to make sure the filter is properly seated. If raw water is bypassing the seal you could have this issue.

 

[Monkeytank]

I pushed the membranes in tight, but I'm going to open them back up and double check.

 

[laverda]

Sounds like the membranes could be hooked up wrong. Are your waste and RO lines mixed up?

 

[Monkeytank]

Maybe that's the problem because I cant be certain I have the output of each housing actually connected to the right line. I looked at the instructions and all I can find are ones that don't answer this. Which end of the membrane housing should be waste and which is RO? Looking at each housing, there are two outputs. One is a little bit molded and pushed out compared to the other. In this case the top one sticks out to the right just a little farther than the bottom one. Which is waste and which is RO?

 

[minus9]

I recently discovered that after upgrading my original 4 stage unit to a 5 stage, then to 6 and now 7, that my tubing was incorrectly routed after my initial upgrade (a couple years ago). I essentially was running the second carbon block after the membranes, instead of before (because I didn't reroute the lines when I added the second CB and second DI). For someone who is so meticulous about this stuff, I somehow overlooked this setup. Although my TDS was always 0 coming out, I was burning through DI resin and probably not getting ultra pure water (which would be the reason I was having some issues with my sps). This may not be your issue, but it's worthing examining your tube routing to be sure the split to the membranes and pressure gauge is after the second carbon block. I'm still PO at myself for this. Ugh!
Anyway, double check everything!

 

[Opus]

Maybe that's the problem because I cant be certain I have the output of each housing actually connected to the right line. I looked at the instructions and all I can find are ones that don't answer this. Which end of the membrane housing should be waste and which is RO? Looking at each housing, there are two outputs. One is a little bit molded and pushed out compared to the other. In this case the top one sticks out to the right just a little farther than the bottom one. Which is waste and which is RO?

The one that sticks out is the RO and the other waste.

 

[Opus]

Are you on well water? Just wondering why you are running a 3 stage DI for such low tds tap water.

 

[Monkeytank]

Thanks Opus! That's probably the issue. I'll check it out tonight.

I'm on city water. I got the three stage after watching a Bulk Reef Supply video and thinking over time I'd save time and money and be sure I was getting everything out with the three stage resin. I make a whole lot of water so I figured it would be worth it in the long run. I have 630 gallons total volume now, plus I'm adding 460 soon. I also grow phyto and pods in many buckets and go through a lot of water with those. Mainly I'm probably just a sucker for a marketing video. It was this one

 

[ca1ore]

If the waste line is blocked or not connected properly then there is no place for the water to go but through the RO membrane and output will approach the same TDS as the input. I used to run my waste to the outside and one time it got frozen up and I had the same problem as you.

 

[Opus]

Thanks Opus! That's probably the issue. I'll check it out tonight.

I'm on city water. I got the three stage after watching a Bulk Reef Supply video and thinking over time I'd save time and money and be sure I was getting everything out with the three stage resin. I make a whole lot of water so I figured it would be worth it in the long run. I have 630 gallons total volume now, plus I'm adding 460 soon. I also grow phyto and pods in many buckets and go through a lot of water with those. Mainly I'm probably just a sucker for a marketing video. It was this one

Well, if you were using a 99% rejection RO membrane your DI would last a very long time. Your 40 would get down to around .4 tds. At that level a DI cartridge would make around 11,000 gallons of 0 tds water. My tap water is around 450 and my tds after the membrane is in the 2 to 3 range.

 

[Monkeytank]

Thanks for the input. I have it fixed now. I got the output and waste lines hooked up correctly and have zero TDS coming out of the membranes now, and it stays at zero through all three DI stage inputs and my final output. My water is pretty cold, so I don't get the output advertised for the ideal test conditions they use for the rating. By switching to the two 100 GPD membranes instead of the two 75 GPD ones, I went from a true rate of 107 gallons per 24 hours to 155.5 gallons per 24 hours. That was even with switching from a single DI resin to a triple one. Both of the sets of membranes were new. I ordered replacement 75 ones to change out my old ones, then decided I wanted to go with the 100's. I went ahead and tested it with both sets to get a good comparison so I'd know how much difference there really was. It was a 45% improvement with the 100's.