Direct RO/DI ATO

[JyB818]

Still planning my 150 gallon tank build. One thing I'm considering is having a "T" in my RODI output line. One running my RODI directly into the sump with a float valve like this
https://www.bulkreefsupply.com/auto-shut-off-kit-for-reverse-osmosis-systems.html
and the other line accessible with a manual valve to fill a container for mixing saltwater for water changes.

I live in a 2-story townhouse that has no basement. Directly above where I plan on putting the tank is my laundry room. So my thought is to put the RODI unit in there and run a line through the wall and exit under the tank.

Is this a good idea?

My thought is then I don't have to have a separate ATO water container or the additional plumbing, wiring, etc.

Give me the PROS and CONS of doing something like this.
Con #1 is that I live in a townhouse with no basement. Which means I have no floor drain if something fails.

Thank you

 

[MaddyP]

If it were me, I would run the RODI to a small container (2-5 gallons) next to the aquarium and then pump from this container to the aquarium. My reasoning is this: if the float fails it will overflow the container. Yes, it will make a big mess, but at least it crash your tank in addition to making a big mess.

I am also running my RODI about 12 feet above my tank in a loft area. You can check out my build thread, maybe it will give you some ideas?

https://www.reef2reef.com/threads/75g-rimless-crystal-dynamic-build-thread.296722/

 

[cmcoker]

Not a good idea, imo. The frequent cycling will let TDS creep burn through di resin.

That's the cheap version of problems, the expensive version is when you come home to a fresh water tank and flooded townhouse

 

[TbyZ]

TDS creep

 

[kashman100]

If the float switch fails to work and rodi water stays on you will have a flood and/or tank crash. Also its my understanding that the di resin doesnt last near as long when constantly turning on and off making small amounts of water from tds creep.

 

[Greybeard]

IF you're going to go direct from your RO/DI to your sump, do so with redundancy, and failure in mind.

RO/DI to a Solenoid valve, controlled by a float switch, then to a float valve, positioned slightly below the float switch... this would give you one layer of redundancy. If the float valve fails, the float switch should catch the problem. Plug the solenoid into a controller so that it can't run more than X minutes per day, and you've added a 2nd layer of protection.

You've still got what's known as TDS Creep to worry about... RO/DI units operate much more efficiently if they run for a decent length of time, rather than coming on for a few minutes, or seconds, even, and then turning off again.

The way around that problem would be to use a small reservoir, refill it from your ATO every few days, and from there to your redundant ATO system.

Here's my solution:
RO/DI to a solenoid. Solenoid is powered by my controller, and only on 2 hours, twice a week. Power for the solenoid also runs through a float switch in the ATO reservoir, so that it turns off if the float switch is ever tripped, which it shouldn't be. Water goes from the solenoid to a float valve in the reservoir. This is the primary shut off. If it fails, the float switch would be tripped, cutting power to the solenoid, and shutting off the water before the reservoir overflows. Reservoir is 5 gallons. I use about 2 gallons a day. Reservoir is automatically refilled on Monday and Thursday, by the timer on my controller. From there, a Tunze ATO, with it's redundant optical and mechanical sensors, it's overfill alarm, and it's own overrun timer, maintains sump level.

Oh, and I have a cheap Amazon battery powered water alarm on the floor under the sump, just in case everything else fails.

Result? No TDS Creep, since the RO/DI runs for 90 minutes or so twice a week. No worries about flooding the house, or flooding the tank, and I _never_ have to manually fill anything. I check the sensors, switches, and float valves for proper function when I do my weekly maintenance. Just to be sure nothing has failed.

 

[JyB818]

If it were me, I would run the RODI to a small container (2-5 gallons) next to the aquarium and then pump from this container to the aquarium. My reasoning is this: if the float fails it will overflow the container. Yes, it will make a big mess, but at least it crash your tank in addition to making a big mess.

I am also running my RODI about 12 feet above my tank in a loft area. You can check out my build thread, maybe it will give you some ideas?

https://www.reef2reef.com/threads/75g-rimless-crystal-dynamic-build-thread.296722/

Thank you. I only considered the mess. I didn't think about killing the tank.

 

[JyB818]

Not a good idea, imo. The frequent cycling will let TDS creep burn through di resin.

That's the cheap version of problems, the expensive version is when you come home to a fresh water tank and flooded townhouse

I'd never heard of TDS creep before. Now I know. Thank you.

 

[JyB818]

IF you're going to go direct from your RO/DI to your sump, do so with redundancy, and failure in mind.

RO/DI to a Solenoid valve, controlled by a float switch, then to a float valve, positioned slightly below the float switch... this would give you one layer of redundancy. If the float valve fails, the float switch should catch the problem. Plug the solenoid into a controller so that it can't run more than X minutes per day, and you've added a 2nd layer of protection.

You've still got what's known as TDS Creep to worry about... RO/DI units operate much more efficiently if they run for a decent length of time, rather than coming on for a few minutes, or seconds, even, and then turning off again.

The way around that problem would be to use a small reservoir, refill it from your ATO every few days, and from there to your redundant ATO system.

Here's my solution:
RO/DI to a solenoid. Solenoid is powered by my controller, and only on 2 hours, twice a week. Power for the solenoid also runs through a float switch in the ATO reservoir, so that it turns off if the float switch is ever tripped, which it shouldn't be. Water goes from the solenoid to a float valve in the reservoir. This is the primary shut off. If it fails, the float switch would be tripped, cutting power to the solenoid, and shutting off the water before the reservoir overflows. Reservoir is 5 gallons. I use about 2 gallons a day. Reservoir is automatically refilled on Monday and Thursday, by the timer on my controller. From there, a Tunze ATO, with it's redundant optical and mechanical sensors, it's overfill alarm, and it's own overrun timer, maintains sump level.

Oh, and I have a cheap Amazon battery powered water alarm on the floor under the sump, just in case everything else fails.

Result? No TDS Creep, since the RO/DI runs for 90 minutes or so twice a week. No worries about flooding the house, or flooding the tank, and I _never_ have to manually fill anything. I check the sensors, switches, and float valves for proper function when I do my weekly maintenance. Just to be sure nothing has failed.

I think this is the route I will go. I was trying to eliminate fail points. It looks like my idea would have achieved that, but the fails would be more costly in the long run. Not worth it.

 

[JyB818]

Thanks to everyone for their input on this. Back to plan A of having an ATO reservoir.

 

[Randy Holmes-Farley Verified Community Expert]

I'd never heard of TDS creep before. Now I know. Thank you.

Just to explain what exactly it is...

The RO membrane is a filter with tiny holes that slow down the passage of things based on size, so water gets through more easily than bigger things such as hydrated ions (sodium, chloride, copper, etc.). So the effluent water has less of the large things in it.

When you turn off the water pressure, water and ions can still slowly cross through the RO membrane. In fact, there is a chemical driving force for ions on the upstream side where they are more concentrated to move to the downstream side where they are less concentrated.

This happens every time you shut off the water flow. If you do that once a week or once a month, you get a certain amount of ions to cross.

If, in a setup with RO/DI connected directly to the tank ATO, you do it every hour, or every 10 minutes, you might get 10 or 100 times as many ions getting through during that time because you do it ten or a hundred times more often.

Those ions then go on to deplete the DI more rapidly.