RO/DI - TDS issues

[popalud]

Thank you for posting the pictures. As you can see from the additional comments, there seems to be an issue with the membrane. Is it safe to assume the kit came fully assembled, and you just added the media and membranes? I ask because I want to make sure the concentrate/reject water line and flush lines were not crossed.

Did you have to flush the carbon blocks when you set it up?


I highly recommend getting a good inline TDS meter. This is one of the two I use.

HM Digital DM-1 TDS Meter

I use two TDS meters. One that monitors input into the system and output of the membrane, and the second that monitors input into the DI and output from the DI. It is very helpful in understanding how the system is performing.

I want to make sure you focus on addressing the TDS creep and the membrane, then we can worry about adding a DI stage, which will be highly recommended for aquarium use of your product water.


Are you in Texas or on well water? Your input TDS is very high in general. I'm in South Florida, where we famously have terrible water, and my tap water is 174 TDS. I usually only see tap water numbers as high as yours in Texas or when people are on a well. That is important because you might need carbon blocks specific to your water chemistry. I, for example have carbon blocks specifically for chloramine and heavy metals, which are present in our water.

kboogie, the system came assembled other than me having to connect the source, discharge, and waste lines, install filters/o-rings, and membranes. Per the directions, I flushed the system with the bypass valve open for about 3 min, then ran the system at about 45-50psi (best i could get with my initial setup) for about 30min and discarded that water.

I've ran the system for another 5 hrs last night at 60ish psi, which produced about 2g of filtered water/hour. TDS remained around 80ppm every test (about 6).

I'm in CA and the municipal water provider switches between well and surface water depending on season. Not sure what they are pulling from now, but during my previous FW tank hobbying, I know it is treated and is pretty similar between both sources (high chloromines).

I contacted Aquaticlife today regarding my issues and received a prompt response regarding making sure the filters/membranes are properly seated (check!), and asking me to provide the time it takes to fill 16oz of filtered water (2m20s). He said 60psi should be sufficient.

I asked if there was anything else that would be helpful in troubleshooting and the reply was:
-Membranes fully inserted
-TDS Testing (direct from filtered water). Im using borosilicate glassware and a cheap TDS pen for testing
-"Hot water could not reach the membrane" I asked for clarification as I've never read anything about "hot water" but think he may have meant "not enough water..."
-Then he mentioned the flow rate (time to fill 16oz) would help troubleshoot and he's "concerned the system has 2 separate membranes and for both to no be working indicates some other issue."
-He stated I should be getting 16-18ppm after operating for 3min and that he may want me to bypass each of the membranes to see if one or both are the issue.

Not sure I want to be tearing the system apart considering I've had it for 4 days and there's clearly an issue.

I did order a DI system that I will install once I get TDS to .05%-ish (with an inline TDS meters).

I appreciate the continued help (you too Shirak!)

 

[Shirak]

I think he is asking that you didn't run hot tap water through the RO membranes which would damage them.

Can you take a picture of the other side of this one so we can see how everything is connected? I don't see it in this picture but the Waste from RO housing one should be running into the input on RO housing 2. I don't see a line going there? Additional pictures would help.

I also labelled which connection is RO out and waste out. It's the same for RO housing 1.
You can disconnect the RO out on housing 1 where ever the other side is and collect the RO for a minute so you can test tds. I would then collect RO from housing 2 only to check the tds on that one.

 

[popalud]

I think he is asking that you didn't run hot tap water through the RO membranes which would damage them.

Can you take a picture of the other side of this one so we can see how everything is connected? I don't see it in this picture but the Waste from RO housing one should be running into the input on RO housing 2. I don't see a line going there? Additional pictures would help.

I also labelled which connection is RO out and waste out. It's the same for RO housing 1.
You can disconnect the RO out on housing 1 where ever the other side is and collect the RO for a minute so you can test tds. I would then collect RO from housing 2 only to check the tds on that one.

Here you go. Lots of fitting and routing which is why I’m hesitant on doing much more if there is an issue with what they sent me. No hot water has been used.

 

[kboogie]

I think he is asking that you didn't run hot tap water through the RO membranes which would damage them.

Can you take a picture of the other side of this one so we can see how everything is connected? I don't see it in this picture but the Waste from RO housing one should be running into the input on RO housing 2. I don't see a line going there? Additional pictures would help.

I also labelled which connection is RO out and waste out. It's the same for RO housing 1.
You can disconnect the RO out on housing 1 where ever the other side is and collect the RO for a minute so you can test tds. I would then collect RO from housing 2 only to check the tds on that one.

Here you go. Lots of fitting and routing which is why I’m hesitant on doing much more if there is an issue with what they sent me. No hot water has been used.

Is it me or does it look like they ran the membranes in parallel and not series.

If it is parallel that would be an explanation because that would create lower pressure at the membrane, making high static pressure a requirement.

If you could send it back ai would consider sending it back and getting a Buckeye or BRS unit.

 

[Shirak]

@kboogie They do appear to be in parallel. Would need some really good pressure and flow for that set up. Not sure if that would fully explain the almost 80ppm tds on the RO though. Maybe? It could be redone in series but I think it's best to check both membranes individually to see what they are putting out on RO tds.

@poplalud disconnect the two RO lines going to the T at the auto shutoff valve. Get a couple small containers and collect the RO from each and check tds.

Let them run for a few minutes after turning on and before collecting the two samples.

You could also disconnect at the RO housing if you have some longer spare tubing and wanted to connect there instead to collect samples from each RO.

 

[popalud]

@kboogie They do appear to be in parallel. Would need some really good pressure and flow for that set up. Not sure if that would fully explain the almost 80ppm tds on the RO though. Maybe? It could be redone in series but I think it's best to check both membranes individually to see what they are putting out on RO tds.

@poplalud disconnect the two RO lines going to the T at the auto shutoff valve. Get a couple small containers and collect the RO from each and check tds.

Let them run for a few minutes after turning on and before collecting the two samples.

You could also disconnect at the RO housing if you have some longer spare tubing and wanted to connect there instead to collect samples from each RO.

@kboogie They do appear to be in parallel. Would need some really good pressure and flow for that set up. Not sure if that would fully explain the almost 80ppm tds on the RO though. Maybe? It could be redone in series but I think it's best to check both membranes individually to see what they are putting out on RO tds.

@poplalud disconnect the two RO lines going to the T at the auto shutoff valve. Get a couple small containers and collect the RO from each and check tds.

Let them run for a few minutes after turning on and before collecting the two samples.

You could also disconnect at the RO housing if you have some longer spare tubing and wanted to connect there instead to collect samples from each RO.

Update- I tested the last 5 gal (in food safe bucket) of filtered water prior to testing each membrane independently. Last 5g of filtered water produced is 38ppm. I then tested each as suggested above after running/flushing for 5min after disconnecting them. Both read 27-28ppm. Since I haven't changed anything other than running water through the system (estimating about 30g of filtered before seeing the TDS significantly improve), am I to assume that the system is getting "flushed" and after a few more gallons, I'll be near 0ppm? Also, at what point (in TDS ppm) would using a DI system be beneficial? Thanks!

 

[Shirak]

ok @poplalud so both membranes are working, but not working great. I don't think flushing will make much difference at this point. New membranes need to be flushed but it really should only take 30 min or so initially for them to get up to peak performance. Once they are flushed it only takes a few minutes to eliminate tds creep from the RO lines each time the unit is turned on after sitting idle.

Leads me to believe it's pressure and flow into the RO housings. Looks like they are measuring pressure before the split to feed the two membranes. That basically means your pressure and flow is much lower than your pressure gauge is reading because of the parallel flow they have plumbed.

One more thing to try and see if it helps... run a single RO membrane. If you could disconnect the line coming out of the T and going to RO housing 1 and then disconnect the T from the auto shutoff valve and plug the RO housing 1 line directly into the auto shutoff valve. Then disconnect the RO output line from the other T and collect a sample as you did previously. See if that makes a difference in tds.

 

[Shirak]

Would be nice to know what membranes are in the unit. Less expensive 95% rejection membranes should still give you around 22ppm RO water. 98% would be around 9ppm. Do you happen to know manufacturer and which membrane? Rejection rate on really hard water may be less than ideal. 430ppm tds source water is pretty hard. Probably a lot of calcium and magnesium. Do you have a water report from your local water company? Should be available online. Lower pressure will also reduce rejection rate. Higher GPD membranes of the same size tend to have lower rejection rates as they allow more water through. So number of factors affecting your results.

 

[popalud]

@kboogie They do appear to be in parallel. Would need some really good pressure and flow for that set up. Not sure if that would fully explain the almost 80ppm tds on the RO though. Maybe? It could be redone in series but I think it's best to check both membranes individually to see what they are putting out on RO tds.

@poplalud disconnect the two RO lines going to the T at the auto shutoff valve. Get a couple small containers and collect the RO from each and check tds.

Let them run for a few minutes after turning on and before collecting the two samples.

You could also disconnect at the RO housing if you have some longer spare tubing and wanted to connect there instead to collect samples from each RO.

@kboogie They do appear to be in parallel. Would need some really good pressure and flow for that set up. Not sure if that would fully explain the almost 80ppm tds on the RO though. Maybe? It could be redone in series but I think it's best to check both membranes individually to see what they are putting out on RO tds.

@poplalud disconnect the two RO lines going to the T at the auto shutoff valve. Get a couple small containers and collect the RO from each and check tds.

Let them run for a few minutes after turning on and before collecting the two samples.

You could also disconnect at the RO housing if you have some longer spare tubing and wanted to connect there instead to collect samples from each RO.

Worked with customer service and they are sending new membranes. Hoping that fixes the GPD and TDS issue. I’ll update once I’m up and running again! Thanks all!

 

[Shirak]

I will cross my fingers but I fear it's unlikely a membrane issue if both were working equally. I think we should get another expert opinion..

Russ @Buckeye Hydro what is your take on a 200gpd RO system running two 100gpd membranes in parallel? 430ppm tds source water at about 55-60 psi out of the tap. OP measured about 30ppm tds out of each membrane individually after many hours and gallons of water run through the system. I think initially was reporting around 70-80ppm tds out of the combined RO line.

Pressure and flow problem with parallel plumbed?

Just a bad cheap hand held tds meter??

 

[Buckeye Hydro]

Based on a quick gaze over the thread, here are my thoughts:
1. Unlikely to be a bad TDS meter. Meter may need to be calibrated.
2. Don't take TDS readings out of a bucket.
3. With 430 ppm TDS feedwater, you'd absolutely not want to run two membranes in series in an RODI system like the OP wants to set up. No doubt he has high hardness and you'd toast the second membrane.
4. I didn't see what membranes were installed. There are all sorts of low end membranes available on the market - I don't know what's in this system. At what pressure were they spec'ed?
5. What flow restrictor was used on each membrane?
6. We can get him set up with a 1, 2, or 3+ stage DI with mixed bed or separate bed resins

Russ

 

[Shirak]

Hi Russ thanks for jumping in. I don’t know what membranes. Apparently replacements are being sent. @poplalud can post a picture of them when they arrive?

what’s the effect of running them in parallel Russ? That is how they are currently configured.

You mention not reading tds out of a bucket. What’s a better way with a hand held meter?

 

[popalud]

Would be nice to know what membranes are in the unit. Less expensive 95% rejection membranes should still give you around 22ppm RO water. 98% would be around 9ppm. Do you happen to know manufacturer and which membrane? Rejection rate on really hard water may be less than ideal. 430ppm tds source water is pretty hard. Probably a lot of calcium and magnesium. Do you have a water report from your local water company? Should be available online. Lower pressure will also reduce rejection rate. Higher GPD membranes of the same size tend to have lower rejection rates as they allow more water through. So number of factors affecting your results.

I'm assuming they will send me 2 of these... I collect water directly from end of the filtered line into borosilicate glass ware and use the TDS pen I got from amazon for under $10.

 

[popalud]

Based on a quick gaze over the thread, here are my thoughts:
1. Unlikely to be a bad TDS meter. Meter may need to be calibrated.
2. Don't take TDS readings out of a bucket.
3. With 430 ppm TDS feedwater, you'd absolutely not want to run two membranes in series in an RODI system like the OP wants to set up. No doubt he has high hardness and you'd toast the second membrane.
4. I didn't see what membranes were installed. There are all sorts of low end membranes available on the market - I don't know what's in this system. At what pressure were they spec'ed?
5. What flow restrictor was used on each membrane?
6. We can get him set up with a 1, 2, or 3+ stage DI with mixed bed or separate bed resins

Russ

Thanks Russ!
1-I'll look into it. I paid $10 for the one I got on Amazon. Not sure I want to spend $10 to calibrate a $10 meter. Is there a good option to look at, maybe an inline setup?
2-I collect from the filtered line into borosilicate.
3-The system is as sent from the manufacture. If the new membranes they send me improves both TDS and flow to what is advertised, I'll look into tweaking to improve longevity. Yes, hardness is an issue in the water source.
4-How does one find flow restriction info?
5-If the new membranes theyre sending me don't drastically improve TDS/flow, I'm returning it and will look for a different system.

 

[Shirak]

According to their website it's supposed to be 98% rejection TFC membrane... so I dunno. Sure hope swapping the membranes solves it.

 

[popalud]

According to their website it's supposed to be 98% rejection TFC membrane... so I dunno. Sure hope swapping the membranes solves it.

Agreed. The CS guy was helpful but perplexed as well.

 

[Buckeye Hydro]

Hi Russ thanks for jumping in. I don’t know what membranes. Apparently replacements are being sent. @poplalud can post a picture of them when they arrive?

what’s the effect of running them in parallel Russ? That is how they are currently configured.

You mention not reading tds out of a bucket. What’s a better way with a hand held meter?

If parallel, you need twice the feedwater flow, and each membrane should have its own flow restrictor. So with adequate flow/pressure, you'll get permeate twice as fast, at a lower TDS than plumbing in series.

For TDS measurements with a handheld meter, collect the water you want to assess in a clean glass container. Rinse the container 3 times with the water you want to measure.

 

[Buckeye Hydro]

I did a little searching... looks like a no-name membrane. When I see that I assume low-cost import from China... Filmtec membranes have a reputation for being the best for a reason.

I'm assuming they will send me 2 of these... I collect water directly from end of the filtered line into borosilicate glass ware and use the TDS pen I got from amazon for under $10.

 

[Buckeye Hydro]

Is there a good option to look at, maybe an inline setup?

Inline meters are good because they are convenient, and over time people end up using them more than handhelds. I'll point you to our DM1, DM2, DM3, and TRM1 inline TDS meters. The DM2 and DM3 offer independently, digitally calibrated probes. https://www.buckeyehydro.com/in-line-1/

4-How does one find flow restriction info?

Flow restrictors, by definition, restrict flow in the concentrate tube. So trace the concentrate tube from each membrane housing and see what you see. You may have "barrel type" restrictors - inline plastic ~1/2" diameter tubes with a flow restrictor inside, or you may have capillary tube restrictors INSIDE the concentrate tube. Remove the concentrate tube from the fitting at the RO membrane housing and see what you see. If you can't find the restrictors inside of about 15 seconds, give us a call when you are in front of your system.

5-If the new membranes theyre sending me don't drastically improve TDS/flow, I'm returning it and will look for a different system.

We're here to help when you need it.

 

[Buckeye Hydro]

What a joke! Here's what I found about the membrane on the aquatic life website. The specifications section is blank. Nada. So who knows what you're getting!