RO plumbed straight to sump? Good or bad idea?

[smokin'reefer]

I am in the process of setting up a new rimless tank. As some of you are well aware of, evaporation rates on these are crazy.

My last tank was a Reefer 450 and I had the RO line go directly to my float switch with no issues. As far as my rookie self knew anyway.

Because the location of my knew tank, it would be tricky to run the RO tube from my 7 stage RO-DI set-up. New house has a slab for where as the old one had a crawl space to run lines where ever needed. At one time I had my 450 reef, a 350 predator tank and a biocube on a network.

With the new circumstance I was thinking of having a RO buddy 4 stage with DI just to feed tank evaporation. And just use larger kit for water changes and such.

Anyone have any experience or opinions with this type of setup?

TIA

 

[Tuffyyyyy]

I don’t think there’s anything wrong with it

 

[ca1ore]

Generally frowned upon. Cycling RO system frequently will burn through DI faster and having an ‘infinite’ reservoir is just asking for problems. I wouldn’t do it.

 

[ShepherdReefer]

I built an 400ish gallon tank for a church many years ago, I had the RO machine feeding the tank directly for evaporation. Worked great. Although, I did have two different float system to keep from overfilling the sump.

 

[tsouth]

I would not recommend it - not because I have experience in it, but rather because I've seen or heard stories of switches getting gunked and therefore overflowing the tank due to a freshwater fill.

Another thought - what if your resin runs out and now the water you're pumping into your tank directly has a generous increase in TDS? Algae!!!! (I'm such an over exaggerator)

Do you really think it's worth the risk? What if you had a separate container and ran the line to there, and setup the ATO from there. Then, if you flood anything, at least it was just a RO container and not your tank right? If you're starting from scratch - consider taking this opportunity to do things safer.

To add to this: Many containers are built with 1/4" Ro line fittings or you could even install your own. So as long as your reservoir is above the float switch height, it will work as expected.

 

[savoyard]

I built an 400ish gallon tank for a church many years ago, I had the RO machine feeding the tank directly for evaporation. Worked great. Although, I did have two different float system to keep from overfilling the sump.

I'm in a similar situation. How did you setup two different float systems to keep from overfilling the sump?

 

[mfinn]

As mentioned the constant starting and stopping the rodi would burn through di resin pretty fast. Plus the possibility of turning your salt tank into a freshwater tank is a real thing.

 

[Leslie Tabor]

My ATO has done funky things in the past, but fortunately I only had a small amount of water to burn through. I would worry about extended times away...work, vacation etc. It sounds like you plan on a few fail safes but my anxiety/nerves would not like knowing there is a never ending supply of freshwater hooked to my tank!

 

[smokin'reefer]

I'm in a similar situation. How did you setup two different float systems to keep from overfilling the sump?

I know you can use a back up detector like on a Tunze osmalator to shut off in case of overflow. I never had this issue with my other set up using the stock float that came with the reefer tanks.

BTW, I just used regular tees and separate float switches on each tank. Biocube had the 3155 osmalator to control flow.

 

[Matt Peacock]

Well the main risk is that you are linking your sump to the mains water supply, which never stops. A failure of a float switch could wipe out your tank or even your home. One thing I would say about major leaks/floods is that most people think it only happens to others.

To avoid the flooding issue and the points about membrane cycling and TDS (the concerns are correct - you'll really chew through resin), can you not put a reasonably-sized water container in the floor space? You can then fill this from your RO system, which you can turn on and off (i.e. disconnecting your tank from the mains and ensuring you 'batch' create water to avoid the TDS issue), and have a 12V ATO pump bringing it up out of the container into your sump. You would have to ensure that the ATO output tube is high enough so that in the event of a return pump failure, you do not create a siphon.

 

[smokin'reefer]

I ran this set up on other tanks for more than two years with no issues as far as overflowing with water. I definately understand stand everyone's concerns and opinions on that part of this type of configuration.

I have read you can have a bit of TDS creep from RO units because of constant cycling as others have stated. And burning thru resin seems to be a valid point also. I believe these smaller units have a clear can for the DI but everything else seems to be in sealed tube. Might need to change filters once a month til I can see how bad they are being spent.

My 450 seemed to evap about 4 or 5 gallons every 3 or 4 days. My new tank oil the peninsula 650 so I would guess the evap rate would be a bit higher. I would guess 15 to 20 gallons a week.
It would be hard in my current and ongoing physical limitations to keep refilling the ATO reservoir.

It was a highly contested topic years ago and appears to still be.

 

[Matt Peacock]

Well it's always a balance. I mean most people on forums give advice on what should be done, then log off and 'just quickly' prop an energised extension lead up next to their sump while they're doing some maintenance, or rush through dipping their corals as they've got a busy day ahead etc.

I guess an interim solution is to go ahead with your proposed RO set up, but instead of linking it to the float valve you could link it to the ATO reservoir that comes with the new Peninsula 650. You could do this with an ATO, having one float switch at the very bottom and the other at the top. That would substantially increase the amount of water being produced each time which might reduce the amount of resin you get through.

 

[AZMSGT]

Bad idea all the way around. TDS creep is real and you will end up with issues like chronic diatoms. If you want top quality water for your system and you are running a RODI then why mess it up by direct feeding and adding TDS?

Best practice is to fill a ATO tank making say 10-200 gallons at a time. Then pump that water to your tank.

This is why there are so many ATO systems sold today. Because it works best.

 

[Spieg]

I would definitely plumb the RODI to the ATO rather than directly to the sump. Too much crud build up in the sump for me to trust any shutoff switch to function reliably over time. The ATO reservoir is just pure clean water so switches perform pretty well there... and as stated you can let the ATO reservoir run pretty low and just turn on the RODI once a week to refill and help preserve your DI resin (and prevent any risk of overflowing the tank). You can even automate this with a good tank controller.

 

[Saltyreef]

I ran this set up on other tanks for more than two years with no issues as far as overflowing with water. I definately understand stand everyone's concerns and opinions on that part of this type of configuration.

I have read you can have a bit of TDS creep from RO units because of constant cycling as others have stated. And burning thru resin seems to be a valid point also. I believe these smaller units have a clear can for the DI but everything else seems to be in sealed tube. Might need to change filters once a month til I can see how bad they are being spent.

My 450 seemed to evap about 4 or 5 gallons every 3 or 4 days. My new tank oil the peninsula 650 so I would guess the evap rate would be a bit higher. I would guess 15 to 20 gallons a week.
It would be hard in my current and ongoing physical limitations to keep refilling the ATO reservoir.

It was a highly contested topic years ago and appears to still be.

My uncovered 40 breeder goes thru 5 gallons per week so the 450 evap rate isnt that much....
I dont have problems with refilling my 5 gallon auto top off container weekly with batch made DI.

FWIW
Only 5 gallons of DI water being overfilled has caused my tank to crash twice and about 5k in damage to my home.

Id hate to see the "other side of the fence" when your "infinite reservoir" decides it finally wants to misbehave after never doing so.
As said above, it seems like a distant reality when it hasnt happened to you before.

 

[savoyard]

Does an Auto shut off on the RO prevent it from cycling through the TDS? Sorry if this is a dumb question as I haven't installed an ASO yet.

 

[Crustaceon]

You’re at the mercy of yet another switch or solenoid that can fail and nuke your tank. We want to minimize those and not add to them. I wouldn’t do it.

 

[Sisterlimonpot]

TDS creep and faulty level sensors are the 2 main reasons this is a bad idea.

As mentioned many times already in this thread, you will spend quite a bit more on your annual budget for DI resin. Having the RODI unit kick on once a week to fill a large container vs cycles on xx times a day will keep your membrane cleaner longer it will also prolong the life of the DI resin.

Faulty level sensors are also a huge concern, even if you have redundancy built in, it's inevitable that they will fail. In the past I've overfilled my sump many times because of this. You never know when a float switch will hang up or when an optic sensor will fail to report proper conditions. I personally use 3 level sensors as well as add an extra container to my top off system.

I personally have my RODI fill a 55 gallon drum twice a week, and a pump inside that drum fills a 10 gallon ATO reservoir, that way if the sensors dont work properly, it can only pump 10 gallons into to sump (not 55). I can't imagine the problem if you have the RODI with endless amount of water continue to pumps into your system. Actually, I can, i used to read it all the time from other members. That's why the older more experienced reefers are raising the red flag and saying this is NOT a good idea.

 

[Crashjack]

I attached my RO unit to my washer line and hung in our laundry room and then ran the line through the attic and dropped down the wall the tank backs up to. It fills both my ATO reservoir and mixing station. I have ball valves on each so I control but also have float switches in each as a back up. It works well because my ATO reservoir fills to 9 gallons and then I close the valve. Therefore, the maximum amount of water I could ever introduce to the display is 9 gallons, and that would have to be right after I filled. I have other failsafes in that I use a dosing pump for my ATO, and I’ve programmed my controller to automatically shut the pump off if it runs over so much time. I typically fill the reservoir every 4-5 days. I also receive an email if the ATO pump times out, which also lets me know it is time to refill the reservoir. The system is very automated with several failsafes and with me being physically handicapped, it has worked well for me.

 

[Sisterlimonpot]

Does an Auto shut off on the RO prevent it from cycling through the TDS? Sorry if this is a dumb question as I haven't installed an ASO yet.

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.