Rodi sytem remodel

[RandyStacyE]

This topic is a well worth while DIY for most anyone with an RO/DI unit if the purpose is understood. I’ve seen other DIY methods that help keep the TDS creep down by stopping the unit from briefly kicking on then off therefore supposedly helping with this TDS creep, but this evidently solves the problem entirely! Just another gallon of waste water is nothing in comparison to the amount of TDS that can slip by due to a brief ‘kick on then off of a RO/DI unit’.

It sounds like that timer board is the key. Would the makers happen to make them for resale or are they custom made only and what did that cost? A reference # or something would be great for anyone wanting to do the same thing.

I’ve seen what you have done with the optical sensors, do you think that it is possible to create the same result by directing the RO/DI output into an appropriate size/1 gal reservoir, when this reservoir is full a sensor will open a small bottom drain (to waste) while simultaneously opening a redirected port for automatic top off or RO/DI main reservoir?

Basically allowing the RO/DI unit to run until a certain volume of water is produced (being until a very small reservoir is full) then tripping waste/gravity drain for the reservoir at the same time tripping an opening to redirect the output to allow the RO/DI output to top off the sump (or main reservoir)?

It was just a thought; it would probably be too complicated and involve too many solenoids or something. The timer and pressure sensor sounds great and likely the most cost effective way to go about solving this problem. High tech is usually cheaper anyway. Congratulations!

 

[DonW]

This topic is a well worth while DIY for most anyone with an RO/DI unit if the purpose is understood. I’ve seen other DIY methods that help keep the TDS creep down by stopping the unit from briefly kicking on then off therefore supposedly helping with this TDS creep, but this evidently solves the problem entirely! Just another gallon of waste water is nothing in comparison to the amount of TDS that can slip by due to a brief ‘kick on then off of a RO/DI unit’.

It sounds like that timer board is the key. Would the makers happen to make them for resale or are they custom made only and what did that cost? A reference # or something would be great for anyone wanting to do the same thing.

I’ve seen what you have done with the optical sensors, do you think that it is possible to create the same result by directing the RO/DI output into an appropriate size/1 gal reservoir, when this reservoir is full a sensor will open a small bottom drain (to waste) while simultaneously opening a redirected port for automatic top off or RO/DI main reservoir?

Basically allowing the RO/DI unit to run until a certain volume of water is produced (being until a very small reservoir is full) then tripping waste/gravity drain for the reservoir at the same time tripping an opening to redirect the output to allow the RO/DI output to top off the sump (or main reservoir)?

It was just a thought; it would probably be too complicated and involve too many solenoids or something. The timer and pressure sensor sounds great and likely the most cost effective way to go about solving this problem. High tech is usually cheaper anyway. Congratulations!

I dont think the resevoirs would be worth the effort. The timers are about $30 and the switch is $20. The mods to the board are already into their production boards and are already being distributed. Do a quick seach for a elk690, you'll find them all over the internet. The switch is a omega psw23-20 twenty being the cut off pressure or contact closure pressure.
This can also be done with any plc or automation controled system much easier and cheaper but I wanted to eliminate a run of cat 5 so I made it stand alone.

Don

Don

 

[RandyStacyE]

Cool! that's some good info! I had no clue what the timer board cost and it's a relief that it isn't too pricy. Sounds worth while.

 

[DonW]

Now that I finished this project, I got a email back from Dow (cut and paste below) replying to my questions about tds creep over a month ago. Seems that all that needed to be done is put a solenoid on the membrane flush valve and a pressure switch to tell the board that the system is shutting down and needs to be flushed. Its all about the shut down not the start up like I thought.
So basicly when the ato shuts off the pressure switch hits 20psi, opens the flush solenoid for 2 minutes. The asv shuts down the unit when the pressure hits 90% then the flush solenoid closes and waits til next time. The period between 20psi and 90% is plenty of flush time and is yielding the same results as the purge. The only real difference is that only one solenoid is needed instead of three.

Don


"Sorry for the very late reply. Although purging the first pint will accomplish what you are trying to do, its unnecessary.
Following the proper shut down procedure for the RO membrane is always best. Most if not all home membranes are not shut down properly and suffer from poor water quality and premature membrane failure.

The proper steps are:

Close outlet faucet or valve
Open flush valve
Close input valve. Either at source or with a 90% auto shut off valve.

The membrane must be used at least once every 24 hours or disinfected prior to next use."

 

[Fahz]

Hi guys this is Jim from the Filter Guys, Randy connected me to the thread. TDS creep or burst is a problem as you know with on off on off systems. Without a doubt it will lead to earily failure of the membrane and rapid exhaustion of DI resin. I think what you have come up with would be of great interest to many people who are having topoff issues. Have you tried the information supplied by Dow to see if it makes a difference? I was going to do some testing of my own but can't seem to find the time.

I have not timed the creep period at startup other then with my dual tds meter but it is less then a minute and a minute would be long enough for a flush period.

Jim

 

[Scooterman]

Sounds like if you start-up & shut down in the proper order you won't have this problem. I don't know how you disinfect the membrane other than a flush?
Welcome to RF Jim, always glad to have extra support.

 

[Fahz]

Sounds like if you start-up & shut down in the proper order you won't have this problem. I don't know how you disinfect the membrane other than a flush?
Welcome to RF Jim, always glad to have extra support.

Thanks I've been around for a while just never realized I had never posted before and was registered under my old screen name. What Dow is suggesting is an RO flush and not a flow restrictor bypass flush I do believe and there is a difference.

Jim

 

[DonW]

Thanks I've been around for a while just never realized I had never posted before and was registered under my old screen name. What Dow is suggesting is an RO flush and not a flow restrictor bypass flush I do believe and there is a difference.

Jim

Jim,
I did some more testing last night. If you follow dow's shut down process you get almost exactly the same results as purging the first pint or so. I get the same results either with a restrictor bypass and flushing with rodi effluent.

So just using the timer board to bypass the restrictor works just fine with this sequence. Conductivity remained 0 at start of each cycle following.

Ato opens ato solenoid
Sump tops off
When full ato solenoid closes
Pressure rises to 20 psi
Restrictor bypass opens for 20 seconds
Pressure rises to 90%
ASV shut down rodi unit

The 20 seconds was just a guess and worked, so I'll test to see how less time effects the conductivity later this week.

Don

 

[DonW]

Sounds like if you start-up & shut down in the proper order you won't have this problem. I don't know how you disinfect the membrane other than a flush?
Welcome to RF Jim, always glad to have extra support.

Scooter the shutdown sequence with the flush at the end works great. As far as cleaning the membrane goes its a drawn out fairly complicated process. I really could not even justify doing it, would just be easier to call Jim and get a new membrane.
Even if your not using the rodi every 24hrs it would be simple to set up to run on a timer just to help keep the membrane clean.

Don

 

[Scooterman]

This post clarifies a lot with me, I wasn't understanding what was going on, thanks for the information, I just dump the RO/DI in 6 gallon cans, I do flush often but not every single time I make water, so now when done I'll bypass the restrictor for 20 30 seconds. I do plan on running tubing up the wall & to the ATO solenoid, so that part is easy, all I need to do is automate the rest, I can do that with the Siemens PLC, dam something else I need to do LOL, it will happen in time. At least now I'm aware of what is needed to happen & what order.
Yes I'll be replacing filters soon, so I'll go through the filters guys web site & order a few things at once.

Jim,
I did some more testing last night. If you follow dow's shut down process you get almost exactly the same results as purging the first pint or so. I get the same results either with a restrictor bypass and flushing with rodi effluent.

So just using the timer board to bypass the restrictor works just fine with this sequence. Conductivity remained 0 at start of each cycle following.

Ato opens ato solenoid
Sump tops off
When full ato solenoid closes
Pressure rises to 20 psi
Restrictor bypass opens for 20 seconds
Pressure rises to 90%
ASV shut down rodi unit

The 20 seconds was just a guess and worked, so I'll test to see how less time effects the conductivity later this week.

Don

 

[DonW]

I think what you have come up with would be of great interest to many people who are having topoff issues. Have you tried the information supplied by Dow to see if it makes a difference?

Jim

Most folks are not real receptive to the idea. Which of course will help your business. My reasoning for looking into tds creep is more long term reef related. Since they are solids and are being put into the tank, I would assume like anything else they will build up. If I look at my tank for a example the ato is cycling many times throughout the day so if the first pint has solids, well thats about 13 pints of high conductivity water. My water volume is 150 gallons or 1200 pints, so in 93 days Ive added my entire system worth of high conductivity water. Granted you may remove some of that with water changes and skimming, but how much is left after a year or two worth of build-up? Does that make any sense?

Don

 

[Fahz]

Jim,
I did some more testing last night. If you follow dow's shut down process you get almost exactly the same results as purging the first pint or so. I get the same results either with a restrictor bypass and flushing with rodi effluent.

So just using the timer board to bypass the restrictor works just fine with this sequence. Conductivity remained 0 at start of each cycle following.

Ato opens ato solenoid
Sump tops off
When full ato solenoid closes
Pressure rises to 20 psi
Restrictor bypass opens for 20 seconds
Pressure rises to 90%
ASV shut down rodi unit

The 20 seconds was just a guess and worked, so I'll test to see how less time effects the conductivity later this week.

Don

Don Am I missing something here are you flushing the RO water pre-DI where the TDS creep is or the waste line?

Jim

 

[DonW]

Don Am I missing something here are you flushing the RO water pre-DI where the TDS creep is or the waste line?

Jim

I tried a number of different thing they all worked with the same results, all pre-di and all on startup with a 2 hour off time.

First was just to dump the first pint or so down the drain with electric valves each time the system cycled. (easy but doesnt clean the membrane)

Second was complicated. Basicly with electric valves ,remove the membrane and flush it with a pump and rodi water. No restrictor but antisiphons on both sides so when the pump turned off it wouldnt siphon air back. I tried this at 40psi and 60psi. (complicated and expensive would cost more than the entire sytem)

Third was the same as the second but no pump just prefiltered water not rodi.
(same as above but still complicated, way to many valves and uses a automation controller)

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)

Fifth was the same exept with the outlet and restrictor bypass open for 20 seconds just prior to shut down. (same as the fourth but without the increase to 2 at four hours, 0 at 6 hours and 0 at 8 hours)

Results on each one yielded 0 conductivity pre-di at two hours except when the rodi was connected in its oem form and when I reinstalled the 65% asv vs. the 90% asv (that part was over my head).

I talked to a tech support guy from Dow yesterday. Although they suggest method #2 or #3 we are not making pharmacy drugs, so its not justified.
#4 allows a very small amount of "osmotic siphoning" (again over my head)
#5 is the same as #4 but with the pressure being more equal on both sides helps only slightly.
He also stated that filling a tank and using it for the ato would not be the best for the membrane, unless you intend to use the entire tank and refill at least every 12 hours, along with the flush. This is contrary to what is common place in the reefkeeping hobby. (latching setups)

So after all the toying with high tech and wasting a bunch of time #4 is the easiest, cheapest and in the long run most productive for a ato sytem connected directly to the rodi system. The only other test I'm going to try is removing the second membrane. Thats just to see how much difference its making and how it effects a single membrane rodi system.

Don

 

[Boomer]

Don

I did not read all this but this post carbon filter, I hope it is GAC and not a carbon block which will creat BP.

 

[DonW]

Don

I did not read all this but this post carbon filter, I hope it is GAC and not a carbon block which will creat BP.

No, its the good stuff from the filter guys. Makes for great coffee:lol:

Don

 

[Boomer]

Ok that good stuff :lol: At least you buy the best

 

[Boomer]

The final carbon stage is to remove any breakdown of the di's.

Break-down ?? Do you mean releasing ions or the resin falling apart ? A second DI in series would be better. I do not think that GAC will do much for silica, ammonia or CO2/HCO3- that might be leaking out of the DI

 

[DonW]

The final carbon stage is to remove any breakdown of the di's.

Break-down ?? Do you mean releasing ions or the resin falling apart ? A second DI in series would be better. I do not think that GAC will do much for silica, ammonia or CO2/HCO3- that might be leaking out of the DI

Break down meaning the di resin falling apart. Since it shrinks quite a bit by the time it changes colors I would only assume its going somewhere. I dont want it in my coffee. Otherwise it makes the water taste much better.

There are two di's after the two membranes and two gac before the membranes. The second gac is there to insure no chlorine makes it way into the membranes.

Don

 

[RandyStacyE]

Don, do you use your RO/DI water for coffee/drinking?

I'm definitely not an expert, but I've read somewhere that RO is better for the bod. I T-off the line before the DI to fill an RO drinking water reservoir.

I hate to spread bad rumors (if it is untrue), but that is just what I read somewhere so I don't use DI water for household use. I took my kids to the doctor one day and the pediatrician gave me hell about using RO water for household use (on more than one occasion). I thought that was ridiculous because you wouldn’t believe the high TDS in my well water. She said that my kids were lacking ‘fluoride’ because the RO and/or RO/DI unit would remove it if any traces were there to begin with. She then issued the kids a 1 year prescription for chewable fluoride.

I don’t know.

I'll be doing this mod soon, I've got a new tank in progress, I have to consolidate all into one.

 

[DonW]

Don, do you use your RO/DI water for coffee/drinking?

I'm definitely not an expert, but I've read somewhere that RO is better for the bod. I T-off the line before the DI to fill an RO drinking water reservoir.

I hate to spread bad rumors (if it is untrue), but that is just what I read somewhere so I don't use DI water for household use. I took my kids to the doctor one day and the pediatrician gave me hell about using RO water for household use (on more than one occasion). I thought that was ridiculous because you wouldn’t believe the high TDS in my well water. She said that my kids were lacking ‘fluoride’ because the RO and/or RO/DI unit would remove it if any traces were there to begin with. She then issued the kids a 1 year prescription for chewable fluoride.

I don’t know.

I'll be doing this mod soon, I've got a new tank in progress, I have to consolidate all into one.

You dont need to worry about it if your using it for cooking. Coffee, tea, coolaid, beer what ever. You dont want to drink it plain out of tap.

Don