Rodi sytem remodel

[Boomer]

Don

Break down meaning the di resin falling apart

Never heard of that ever

 

[DonW]

Don

Break down meaning the di resin falling apart

Never heard of that ever

I got this one from my dad. Hes a old burn doc that owns a biotech company /skin bank. They are required by the government to run post carbon after their mixed bed resins. But like I said if nothing else it improve the taste.

Don

 

[BuckeyeFldSup]

Don

Break down meaning the di resin falling apart

Never heard of that ever

The resin beads shrink with use - so you not gettting release of broken beads - the beads simply shrink with use.

Russ @ BFS

 

[Willy]

Ok my eyes are starting to glaze over a bit lol.....

I have wondered about tds creep and when to flush, how much etc..

If I'm reading this correctly, you are flushing the system post membrane but pre DI for a period of time each time the unit shuts off? Maybe I misunderstood.

Also my system is one I hook up to the faucet each time I want to make water. Do I want to flush the system pre DI for a period of time before each use?

Sorry if these are redundant questions Don just trying to get it simplified in my head.

 

[Boomer]

The resin beads shrink with use - so you not gettting release of broken beads - the beads simply shrink with use.

I know they shirnk with use. In a properly staged system they should not blow out of the cansiter shrunk or unshrunk into the DI discharge.

 

[RandyStacyE]

Anything new with your setup? Still runnin smoothly and no TDS on startup?

 

[DonW]

Anything new with your setup? Still runnin smoothly and no TDS on startup?

Still good to go.

Don

 

[tentacles]

I have wondered about tds creep and when to flush, how much etc..

If I'm reading this correctly, you are flushing the system post membrane but pre DI for a period of time each time the unit shuts off? Maybe I misunderstood.

Also my system is one I hook up to the faucet each time I want to make water. Do I want to flush the system pre DI for a period of time before each use?

I just stumbled across this thread, and this was what I got out of it too, but I'm not 100% this what he is doing.

 

[ShapeGSX]

I was pointed at this thread by Jim from the Filter Guys. I have an automation fetish as well. Apparently, though, my water filtering fetish isn't as developed as some, since my RO/DI system is only 4 stages.

I've read through the thread and checked out the various solutions.

My RO/DI is different than most since it started out life as a Kenmore RO system for drinking water. It includes a 2.3 gallon pressurized tank for holding product water.

This is the setup:
tap water ->
POLY SEDIMENT FILTER 5 MICRON ->
MATRIKX +1 CARBON BLOCK FILTER ->
50GPD RO resin with auto shutoff ->
2.3 gallon RO water holding tank with bladder ->
DI resin filter ->

tank level controlled solenoid ->
kalkwasser reactor ->
sump

I have 2 float switches in the sump of the tank. One is slightly higher than the other for a failsafe. And the solenoid/float switch setup only gets power for 2 minutes at the top of every hour. Since the holding tank is pressurized, no pumps are required for this system!

Since learning of TDS creep, I have realized that running the system for a short time every hour is going to lead to the exhaustion of my DI resin and the RO resin.

Now, the 2.3 gallon holding tank means that I could actually just calculate how much water I go through in a day and how long it takes to generate 2.3 gallons and simply open a solenoid for a while each day to generate the day's water supply. That would dilute the TDS creep water in 2.3 gallons of RO. The one issue here is that the holding tank is in my basement, and there is some head pressure to overcome to get up to the sump. At some point, the pressurized bladder won't have enough pressure to overcome the head pressure. I have been relying on the tank pressure being high at all times.

You have come up with some great automatic solutions that seem to get rid of TDS creep altogether.

Number 4 seems like the best solution because it is relatively easy.

Fourth was easiest, just open the waste line flush valve/ restrictor bypass with the outlet closed for 20 seconds just prior to shut down. (very simple just using a pressure switch and timer board, but after 4 hours of shut down yielded 2 on the conductivity meter 0 at two hours)

This seems to me that you are just flushing the outside of the membrane with filtered (not RO) water, correct? So, essentially, this is an automatic flushing system. Something that you would do manually if you were manually making filtered water.

So how does this keep TDS creep from happening? Perhaps I just don't understand the premise behind TDS creep.

Also, can you give some details as to how you sense and anticipate the automatic shut down in this scenario?

 

[ShapeGSX]

One more question, are you sure that the timer board is an elk690? There are only 4 search results for that part number on Google, and one of them is this page.

 

[DonW]

First there is no "RO resin". I'm not understanding why you think there is head pressure on a rodi system. You could run the hose around the block your still going to get water. You dont need pumps or a pressrue tank to have a solenoid set-up.
TDS creep is the initial high tds water that is comming from the rodi unit. Diluting it does nothing its till there no matter how much you dilute it.
Almost all TDS creep is taken up by the di resin and uses up the di at a quicker rate.
The idea is to get rid of the high tds water and not allow it to ever get to the di resin. When we talk about short cycling what happens is a membrane will have a certain amount of high tds water usually for the first minute or so. If you topped off with a solenoid every time the water level fell just a small amount essentially every time you top of its going to be with high tds water. There are a few ways around this but what you need to understand is that it take a series of electonics and valves to get the water to the waste while not entering the di resin. Just passing to drain through the resin is defeating since your still eating up the resin.
Since this thread was started my system has evolved to a di flushing system that is flushing the membrane with pure rodi water prior to shut down and is using the initial pass to drain.
Personally I would upgrade your system to a efficient system before attempting anything of this nature. Your missing a few stages that are essential to the life of the membrane and diresin.

Don

 

[DonW]

One more question, are you sure that the timer board is an elk690? There are only 4 search results for that part number on Google, and one of them is this page.

try elk960

Don

 

[DonW]

I will be doing a complete break down on how my current system operates along with all the needed items in the next month or so as soon as my tank is up and running. Its being remodeled yet again to add a continious water change system and a remote calcium reactor.

Don

 

[ShapeGSX]

First there is no "RO resin". I'm not understanding why you think there is head pressure on a rodi system. You could run the hose around the block your still going to get water. You dont need pumps or a pressrue tank to have a solenoid set-up.

The pressure tank does help to get the top-off job done more quickly, but you are right, it is not essential. It does help me with water changes, however, by always having a certain amount of water on hand.

I hadn't considered that the RO system basically has the pressure of the entire city water system behind it. When you see the trickle of water that comes out of the system, it is hard to believe. But yeah, the trickle won't stop with head pressure until I reach the level of the water tower that feeds my house. Stupid for me not to realize this.

TDS creep is the initial high tds water that is comming from the rodi unit. Diluting it does nothing its till there no matter how much you dilute it.
Almost all TDS creep is taken up by the di resin and uses up the di at a quicker rate.

My point was that by using the tank, I can feed water to the sump under pressure without actually having the RO system turn on. So, with proper control (which I do not currently have), I can get TDS creep less often by cycling the RO system less often.

This doesn't eliminate TDS creep on an auto top off system, but it makes TDS creep happen less often. And it will lower the amount of solids that hit the DI resin.

The idea is to get rid of the high tds water and not allow it to ever get to the di resin. When we talk about short cycling what happens is a membrane will have a certain amount of high tds water usually for the first minute or so. If you topped off with a solenoid every time the water level fell just a small amount essentially every time you top of its going to be with high tds water.

Right, but I don't understand how option number 4 avoids this. It doesn't appear to dump the high TDS water at startup. Instead, it automatically flushes the RO membrane with filtered water after the RO process is finished, correct? Does this help with TDS creep? How?

Now, flushing is something that should be done after every RO cycle, so this is a great thing to do, and I will likely set this up. If it also gets rid of TDS creep, fantastic!

There are a few ways around this but what you need to understand is that it take a series of electonics and valves to get the water to the waste while not entering the di resin. Just passing to drain through the resin is defeating since your still eating up the resin.

I'm an electrical engineer, so the valves and electronics are no problem. I've programmed AVRs, 68000s and 68HC11s for small and large control systems (which would be serious overkill for something like this). And I can get my head around the pressure and filtering stuff (eventually ).

Since this thread was started my system has evolved to a di flushing system that is flushing the membrane with pure rodi water prior to shut down and is using the initial pass to drain.

That sounds absolutely ideal. Especially given what the DOW engineer stated in his email to you.

Ideal is great, but if #4 is "good enough," I'll go with that solution.

Personally I would upgrade your system to a efficient system before attempting anything of this nature. Your missing a few stages that are essential to the life of the membrane and diresin.

No doubt. But I would like to maximize the life of the current filtering system as best I can. I'll upgrade the filtering as the budget allows. The auto topoff being fed directly by the RO/DI system has the TDS creep issue, and I'm not going to stop using the auto-topoff. So the TDS creep issue will be present no matter how much filtering I have installed. That is why I'd like to solve it now.

Besides, it is an automation system, and I can't resist.

 

[Scooterman]

Don how bad is creep when you make large quantities as in 30 40 gallons at once then not use the unit for a week?

 

[DonW]

Don how bad is creep when you make large quantities as in 30 40 gallons at once then not use the unit for a week?

That more or less depends on the incomming water supply. I think using a rodi in that manor I wouldnt worry about it at all. I would still flush before and after but I definatly wouldnt automate it.

Don

 

[DonW]

Right, but I don't understand how option number 4 avoids this. It doesn't appear to dump the high TDS water at startup. Instead, it automatically flushes the RO membrane with filtered water after the RO process is finished, correct? Does this help with TDS creep? How?

Now, flushing is something that should be done after every RO cycle, so this is a great thing to do, and I will likely set this up. If it also gets rid of TDS creep, fantastic!

All your doing is blasting off the membrane of the majority of the stuff that is creating the creep. But you have to make sure you bypass this to the drain otherwise it just going to go to the diresin.
Your system moves so slow that just puting some hysteris in your ato system would solve the majority of your problems.
The reason I go through this effort is that my current system evaps 7 to 10g per day and my new system I'm going to try and get it up even higher.

Don

 

[Scooterman]

Funny thing about evaporation, when I crank the A/C unit down the Evap goes way Up LOL, the A/C unit is sucking the moisture out the air & thus allows the air that flows over the surface absorb moisture easier than when the house is stuck at a room temp. of 80, the evep. is way less. Regardless, Filling my large tub once a week is easy enough, I do flush before & after just by habit.

 

[DonW]

I'm just hope to not have to use the chiller. I'm not even going to plumb it in at first, so I hope it works other wise I'll have to pull the sump and install some bulkheads. I'm going to have 4 fans on the back pointed right at the water and the lights will be higher than normal.
I will have the luxury of just pointing a floor fan right at the side of the tank also, we'll see what happens.

Don

 

[Scooterman]

I think If your trying to evap that much water a day, room temperature, humidity has a big impact on how much is being evaporated. With an open hood & higher lights I think normally you won't have issues with fans, you can steady your temps. If you need more evaporation then a dehumidifier, A/C or chiller would be required to get better, IMO.