DI Resin Question?

[MnFish1]

My towns water comes from an large aquafer running beneath it. We buy bottled water for drinking.

Looking back, the highest my incoming TDS has been this year was 560. That day the water coming out of the RO membrane was 49 and the water coming out of the DI was 4.

I think we're mixing up terms here to a degree. AND - if I were in an area where my water was coming out of DI was 4, I would merely install another system in series - you may need a pump. However BRS also sells a system that takes 'wastewater' and puts it through a new system - to decrease wastage of water. In other words - I think there are solutions to the other posters problem (and yours).

 

[MnFish1]

ADVERTISEMENT - I have RO/DI equipment for sale new membranes (75 gpd, carbon, and pre filters - as well as DI powder. If this is not allowed Mods please let me know - but anyone wanting cheap RODI - let me know by PM. @Daniel@R2R

 

[MnFish1]

Just checked with some friends, they have 400+, United States is very large and has a lot of different geography and different water. Some is fine even at 500ppm.

Back to OP's issue, @radiata , what RO membrane are you using? Are you sure it's installed properly? You should be getting closer to 97%+ rejection rate.

You're correct - the systems are designed to handle high input water. Of course - the higher the input - potentially the higher the TDS in the output

 

[KStatefan]

If my RODI input TDS is 420, and the TDS getting through the RO membrane is 47, is it running at a 89% efficiency rate? (Please check my math.) Also, wouldn't an RO membrane efficiency rate be dependent on the amount of TDS going into it?

Math looks right

But I would not accept 89%
Pressure, Temperature, Recovery and Feed concentration will affect the rejection rate.
I aveage 385 tds source water and 98.2% rejection rate.

 

[MnFish1]

Was this a large bag for multiple reloads? If so that would be the issues imo. Air exposure will deplete the di resin from what I understand. Could be wrong though.

I think you're correct - however - the color changes - tell that tale

 

[MnFish1]

Math looks right

But I would not accept 89%
Pressure, Temperature, Recovery and Feed concentration will affect the rejection rate.
I aveage 385 tds source water ond 98.2% rejection rate.

Except - I am not sure there is a rule - whereby the water coming into the DI resin needs to be a certain amount? One needs (IMHO) - to compare - the TDS in the faucet - and the end TDS as the only important issue (the intermediate measures can help with diagnosis)

 

[KStatefan]

Except - I am not sure there is a rule - whereby the water coming into the DI resin needs to be a certain amount? One needs (IMHO) - to compare - the TDS in the faucet - and the end TDS as the only important issue (the intermediate measures can help with diagnosis)

as I said erlier I would not even worry about DI until the 47 coming out of the membrane was fixed.

 

[MnFish1]

Everything points to the membrane.. either it’s exhausted or it’s getting bypassed due to low pressure.. 47 out of a membrane will kill di fast.. it can’t be anything else..

Or it could be installed incorrectly (the RO membrane)

 

[MnFish1]

as I said erlier I would not even worry about DI until the 47 coming out of the membrane was fixed.

Kind of agree - and kind of do not. Its not uncommon - depeneding on the 'dissolved solids' for this number to be high?

 

[MnFish1]

Or it could be installed incorrectly (the RO membrane)

And btw - this is not a criticism - the little rubber/plastic membranes can be folded. In fact I would check a new membrane - see how those measurements come out

 

[KrisReef]

And you wonder why this thread is even made. Yall are trying to filter water that is extremely high and wondering why the DI resin is dead in two days... mad I tell ya!

This should be the end of this thread. We know now what the problem is. Trying to filter 500ppm TDS with an aquarium filter and then wondering why it's not working long...

At this point you need to look into a water softener not a RODI unit.

Else just keep buying resin and RO membranes and burning through them.

My municipal water supply relies on an Ocean desalination plant for 50,000,000/day using R/O as the primary method of filtration. A properly functioning membrane will remove 90%, and upwards of 98% of dissolved solids in source water without much difficulty. The process of reverse osmosis filtration is amazingly simple and efficient with even inexpensive equipment.

 

[Mr. Roboto]

My municipal water supply relies on an Ocean desalination plant for 50,000,000/day using R/O as the primary method of filtration. A properly functioning membrane will remove 90%, and upwards of 98% of dissolved solids in source water without much difficulty. The process of reverse osmosis filtration is amazingly simple and efficient with even inexpensive equipment.

You are talking about a commercial RO unit for drinking water for a city. I am talking about getting a water softener for your house. Two totaly different things.

I never said anything about using large RO units for large applications. I said using small RO units for large applications is not efficient.

 

[Troylee]

You are talking about a commercial RO unit for drinking water for a city. I am talking about getting a water softener for your house. Two totaly different things.

I never said anything about using large RO units for large applications. I said using small RO units for large applications is not efficient.

But they are if set up properly..

 

[Cichlid Dad]

I

If my RODI input TDS is 420, and the TDS getting through the RO membrane is 47, is it running at a 89% efficiency rate? (Please check my math.) Also, wouldn't an RO membrane efficiency rate be dependent on the amount of TDS going into it?

Wow, I'm glad I'm 50-65 ppm going in ro and 1-2 into my di.

 

[MnFish1]

as I said erlier I would not even worry about DI until the 47 coming out of the membrane was fixed.

Like I tried to say earlier - thats not an issue.

 

[KStatefan]

Like I tried to say earlier - thats not an issue.

What is not an issue?

 

[MnFish1]

What is not an issue?

"the 47 coming out of the membrane"

OK - let me edit this - it would BETTER if 47 were not coming out of the membrane - AND - I have questions as to whether the membrane is correctly seated (*but was assured that it was) - in which case, one has to deal with what one gets (assuming the measures are correct)

 

[ReefPig]

My 3 probe TDS meter tells me the TDS is 47 coming out of the RO Membranes and going into the DI. Coming out of the DI it measures 32. I would expect it to be zero coming out.

47 out of the membrane sounds very high to me.
For comparison, mine is 13 when I first start it up, and 8 after a few minutes.

Granted though, different water, different places.

Are you running through carbon block and have you checked for chloramines?
I run three stage prefilter, sediment, carbon block and chloramine block, before the membrane.

 

[Buckeye Hydro Verified Sponsor]

guys... my brain hurts after reading this thread!

Let's back up a bit.
420 ppm TDS tap water is nothing unusual. Yes it is higher than most municipal water, but it is nothing unusual.
In an RODI system it is the RO membrane that removes nearly all of the dissolved solids (TDS). You've probably heard the term "Rejection Rate." This is the percentage of the TDS in the feedwater that a membrane will NOT allow through. So the higher the rejection rate the more pure the permeate (RO water). The lower the TDS in the permeate, the longer your DI resin will last. Filmtec residential membranes (the most commonly used membrane in this hobby) are rated at 98% or 99% rejection.

• So @KStatefan (above) is hitting the nail on the head. First thing to do is make sure the membrane is doing its job. In this case:
• 420 ppm feedwater is yielding 47 ppm permeate.
• 47/420 = 11%
• 100% - 11% = 89%. This is the rejection rate. 89% is horrible... something is wrong with the RO portion of this system.

If you keep sending this permeate to DI resin you'll burn through DI resin very quickly.

So why is the membrane not doing its job? Could be lots of reasons. For example:

• the provided TDS measurement could be wrong - was this TDS creep water being measured?
• pressure could be super low
• membrane could be installed incorrectly
• membrane housing could have an internal crack
• membrane could be bad
• membranes could be configured poorly right from the vendor (you'd not want membranes plumbed in series in this application even if your uninformed vendor tells you it will "save water.")

But clearly, the RO portion of the OP'ers system is the place to focus here. Once we get this situation squared away, the DI resin life will be much more reasonable.

Feel free to give us a call when you're in front of your system if you want help troubleshooting.

Russ

 

[Buckeye Hydro Verified Sponsor]

At this point you need to look into a water softener not a RODI unit.

Else just keep buying resin and RO membranes and burning through them.

420 ppm feedwater is likely to be very hard, but we don't know that for sure. What we need to know is the Total Hardness number.

If the OP'ers Total Hardness is high:
yes - it will shorten the lifespan of the RO membrane
yes - the OP will have bigger issues because the high hardness is also hammering his dishwasher, water heater, washing machine and other plumbing fixtures including the insides of his plumbing pipes.

@radiata - give us a call if you want a quote for a softener. It's an easy DIY install if you have just a bit of plumbing skill.

Russ