RO plumbed straight to sump? Good or bad idea?

[mike550]

Two thoughts here. First, if you’ve done it before and are comfortable with the design then do it again.

Second, what about setting up your RO Buddy to fill a ATO reservoir and use a Tunze RO water controller to manage the water levels in your reservoir and running through your RODI system. Then use a separate pump and sensor system to transfer from your reservoir to your sump. The single failure is if the pump feeding the sump from the reservoir fails “on”. But hopefully you have an alarm or something if the sump gets too full.

 

[savoyard]

It's more of an ion issue inside the membrane, @spectrapure can explain it. The way I remember it, when the RO or RODI shuts off the ions that are normally stopped by the membrane can bleed through and upon startup it will be the job of the DI resin to remove it. If you do that multiple times a day, you'll prematurely deplete your DI, but if you can get that down to only a few times a week, then you wont have that TDS creep.

So the auto shut off is really just to stop waste water. You basically want to make batches of water so you don't waste your DI resin?

It gets confusing, because the BRS site says
"Auto shut off valves (ASOV) are great for reverse osmosis systems and will allow your RO system to automatically turn on and off based on the activation of a float valve."

 

[Spieg]

So the auto shut off is really just to stop waste water. You basically want to make batches of water so you don't waste your DI resin?

It gets confusing, because the BRS site says
"Auto shut off valves (ASOV) are great for reverse osmosis systems and will allow your RO system to automatically turn on and off based on the activation of a float valve."

BRS is in the business of selling stuff (and they sometimes contradict themselves), but I would assume they are saying this is a good option for large RODI reservoirs where you would be draining multiple gallons from it at once into a mixing reservoir (or large ATO reservoir) and the RODI would run for a longer period of time to recover the water used. I've also seen where BRS has said ASOV is not a good choice for direct feed to a tank or sump.

 

[ca1ore]

[QUOTE="smokin'reefer, post: 7450861, member: 66555”]
It was a highly contested topic years ago and appears to still be.[/QUOTE]

Dont actually think it’s particularly contested. Folks that have been in the hobby for more than a year or two will mostly give you the thunbs down.

 

[Crashjack]

The auto-shutoff stops wastewater when the unit isn't running, even though it is still receiving input water. For instance, when my reservoir fills and engages the float switch (I guess technically a float valve) or if I manually close the ball valve on the line going to the reservoir, flow from the unit stops AS DOES the waste water coming from the unit. If the auto-shutoff weren't there, wastewater would continue to run.

 

[LRT]

Interesting. I'm going to have to look in to getting an ATO. I am currently running my 6 stage to float valve in sump. Not having any issues burning through resin and ppm is 0 coming out of unit. The thought of it getting stuck and overflowing sump is scary. But the general ease of not having to babysit and fill 5 gallons of evap everyday has made life simple and cut out the swings that comes with evap. Guess I could accomplish the same with an ATO.
Always more work to do lol!

 

[Seneca]

With reasonable fail safes it's perfectly fine. I use 2 solenoids, 2 mechanical float switches and another optical sensor above the rest to cut off power to the solenoids as well as yet another optical sensor that will cut off my return pump if the sump gets near over flowing.. I also keep the whole thing on a timer that only lets the soleniods open for 30 minutes every other day, which also limits the burn through DI resin.

The key is redundancy.

 

[Spieg]

LOL... funny what different people think of as "reasonable". To me an ATO setup with 2 solenoids, 2 float valves, an optical sensor with power shutoff to the return pump, and a timer control seems far from "reasonable". I'm more of a KISS person myself.

 

[Seneca]

LOL... funny what different people think of as "reasonable". To me an ATO setup with 2 solenoids, 2 float valves, an optical sensor with power shutoff to the return pump, and a timer control seems far from "reasonable". I'm more of a KISS person myself.

What is and isn't reasonable is of course driven by a cost benefit analysis. I run two systems of around 1300 gallons total volume. A few extra valves don't even show up on the bottom line, took maybe 20 minutes to install, while making maintenance more convenient.

I have a 2-325 gallon rodi reservoirs (one doubles for salt mixing) but would need basically the same backup systems in place to use those.

I could make a smaller top of reservoir fed by the larger ones I suppose, but that sounds like one more point of failure to me rather than making things more simple.

I think it's easy to run into problems with insufficient redundancy (in general). Redundancy is how you keep things simple.

 

[Spieg]

Wow, that's quite a system you have there, but I'm not sure your 1300 gallon advise makes sense for the OP's Reefer 450 (92 gallon) setup. Not everyone has that kind of money to burn on needless equipment. I agree redundancy is often important to reliability, but so is thoughtful planning and minimal complexity.
BTW, did you mention you have a return "pump" (as in a single pump) that turns off if the sump gets near overflowing? That seems like a glaring lack of redundancy when that pump fails.

 

[Water Dog]

To be clear... just because one switches from constant cycling by hooking their RODI unit directly to their sump, to making large batches of RODI intermittently doesn‘t necessarily make TDS creep go away. The TDS creep is still there and you need to install a DI bypass valve (3 way valve) between the RO membrane and the DI stage to purge the system of TDS creep upon RODI system start up.

 

[smokin'reefer]

Love everybody's points and all are well received. I will explore more trying to do an ATO setup. I'm not real sure I can make it work due to my floor plan. Funny because laundry room that I converted to my fish room is only 20 ft away. Concrete floors make it a challenge, but I love challenges. That's why I'm a reefaholic.

 

[Eg0790]

Seen it done,worked great also seen it fail sometimes.. Its just not for me, theres just something keeping me from straight plumbing an unlimited supply of water to my tank. I like to sleep at night.

 

[LRT]

To be clear... just because one switches from constant cycling by hooking their RODI unit directly to their sump, to making large batches of RODI intermittently doesn‘t necessarily make TDS creep go away. The TDS creep is still there and you need to install a DI bypass valve (3 way valve) between the RO membrane and the DI stage to purge the system of TDS creep upon RODI system start up.

Can you elaborate and post some pictures of this? Or this valve you speak of? I do like the ease of rodi direct to my sump.

 

[Seneca]

needless equipment

Redundancy is not needless. How much is it you think valves cost? It's not very much. Our livestock is what costs money.

BTW, did you mention you have a return "pump" (as in a single pump) that turns off if the sump gets near overflowing? That seems like a glaring lack of redundancy when that pump fails.

Nitpickery aside, I have two return pumps. But now that you mention it, they are on one circuit, and they shouldn't be.

 

[Sisterlimonpot]

To be clear... just because one switches from constant cycling by hooking their RODI unit directly to their sump, to making large batches of RODI intermittently doesn‘t necessarily make TDS creep go away. The TDS creep is still there and you need to install a DI bypass valve (3 way valve) between the RO membrane and the DI stage to purge the system of TDS creep upon RODI system start up.

I'm not quite following that logic. If you mean TDS creep is inevitable, you're right. If you mean that cycling an RODI 20 times a day vs 2 times a week will deplete DI at the same rate, then there's not logic to that.

I agree that a bypass valve will eliminate excessive DI replacement, but at that point you trading DI longevity for more waste water (which is a good trade off). But to address your main point constant cycling of the RODI unit is inefficient compared to making fewer larger batches at a time.

 

[Water Dog]

Can you elaborate and post some pictures of this? Or this valve you speak of? I do like the ease of rodi direct to my sump.

I use the DI bypass valve to flush TDS creep when making large batches of water. Don’t know how I would be able to adopt this set up where an RODI unit continually cycles throughout the day to feed a sump.

For a more detailed explanation about TDS creep, see my post HERE. A DI bypass is simply a 3 way valve between the RO membrane and the DI stage. Upon startup of a system, I flip the switch to flush the first couple of minutes of high TDS creep water down the drain. Then once the TDS creep is flushed out, divert the clean post RO membrane water, devoid of TDS creep water back through the DI resin stage. This will drastically preserve your DI resin life. It helps having a post RO membrane TDS sensor so you can monitor the TDS creep and RO membrane perforomance.

3-Way Ball Valve with John Guest 1/4" Push Connect

Why does BRS recommend this? The 3-way ball valve is probably one of our most favorite fittings. By swinging the handle from one side to another, you can either turn water flow off completely, or direct it from one direction to another. They work great for fresh and saltwater storage...

www.bulkreefsupply.com

 

[LRT]

Ok I have some testing to do and so see the logic here. My water is hard and any kind of tds coming from my rodi is equivalent to high alkalinity swings. I recently found that out when my 3 stage failed and found alk sitting at 14.3.
Was kind of at the mind set I dont care if I have to change the resin monthly if I achive my goal of pure water. That being said it's not efficient at all and a simple ato would be more cost effective in the long run. Just another project I didnt feel I had time for but would probably only take a half our to set up I guess. And one more piece to the puzzle that could fail. But an added fail safe non the less!

 

[Water Dog]

I'm not quite following that logic. If you mean TDS creep is inevitable, you're right. If you mean that cycling an RODI 20 times a day vs 2 times a week will deplete DI at the same rate, then there's not logic to that.

I agree that a bypass valve will eliminate excessive DI replacement, but at that point you trading DI longevity for more waste water (which is a good trade off). But to address your main point constant cycling of the RODI unit is inefficient compared to making fewer larger batches at a time.

I don’t believe I mentioned anywhere in my post about depletion rates of DI resin one way or another. I just wanted to point out that TDS creep is inevitable whether you‘re continuously cycling on/off or making a large batch all at once and should be purged of you want to preserve and prolong your DI resin life.

From my own personal experience, I can tell you that TDS creep takes time to happen and buildup. I make water about once a week. My incoming TDS is in the 70s. Upon startup, my post RO membrane water reads in the 30s from TDS creep. That gets flushed out via DI bypass. Now sometimes, if I have to go do something for a few hours, I shut the system down, when I come back and resume making water the TDS creep number is relatively low at around 4 to 6, depending on how long the system sat idle, from my normal post membrane TDS of 0 to 1.

I can’t find it, but I’ve read that higher TDS going into DI resin will exponentially deplete the DI resin life. So in my case, is continually cycling 6 ish TDS creep water through my DI resin less efficient than blasting my DI resin with 35 TDS creep water once a week? If it’s true that the higher TDS creep going in exponentially depletes DI resin, than I would have to question whether one method is actually more efficient than the other.

At the end of the day, you must use a DI bypass valve to flush out TDS creep, which was the point of my post. I’m not sure how you would adopt an automatic DI bypass set up on a continuously cycling set up.

 

[Matt Peacock]

So the auto shut off is really just to stop waste water. You basically want to make batches of water so you don't waste your DI resin?

It gets confusing, because the BRS site says
"Auto shut off valves (ASOV) are great for reverse osmosis systems and will allow your RO system to automatically turn on and off based on the activation of a float valve."

Auto shut off kits are best suited to stop flooding, not so much for managing resin usage. So imagine the situation where you're going to do a water change. You set your RO/DI filling a large container, it takes ages as we all know so you wander off for an hour. You think this is a safe absence but when you come back you have a very wet floor. Perhaps the mains water pressure was higher that day or 1 hour became 1 hour 10 minutes. Auto shut off kits are perfect at preventing this.

It gets slightly more complicated if you have a booster pump (need a couple more parts) but still useful.

edit: Just to be clear - I'm speaking of the auto shut off valve kits (which includes a float) and not the valve on it's own which, as Crashjack explained above, as a component essentially recognises that one line (production) is blocked and so transfers that condition to the other line (waste). In order to prevent excess water usage with no useful output.