Tell me what's wrong with my simple ATO

[clm65]

I've read a lot on R2R lately about how important an ATO system is, and I do agree. My question focuses on the actual design of an ATO system, which typically consists of a separate reservoir with fresh RODI water that either gravity drains to the SW system through a float valve, or is pumped in when a level sensor is triggered. My system is a bit different...simpler...which means there is probably something wrong with it that will eventually bite me in the butt.

My tank is on the second floor, and my RODI unit is in the garage below. The tank is a 180g, and I would guess my evaporation rate is in the 1-2 gpd range. I don't have room for a large reservoir below or near the tank. So what I did was run the output of the RODI directly to a float valve in my sump, bypassing a reservoir altogether. I used to have the RODI always in service so that it added water as needed, but recently I added a timer-controlled solenoid valve that opens for 1 hour a day to minimize waste and also provide some protection in case the float valve fails.

The only negatives I can think of include not being able to add anything to the makeup water (additives), and not testing the RODI water before it goes into the tank (although I'm not sure how many people actually test their water before they add it to the reservoir).

The system has been installed this way since I built the house in 2000, so I know it works and has been 100% reliable so far. But since this is not the way most people do it, there probably are more negatives that I am not aware of. So please point out the weakness in my system. Thanks!

 

[dank reefer]

Do you have space in the cabinet or next to the tank to add some sort of reservoir? You could run your rodi line to the res, and then add the additives you would like to add if there are any, then get a traditional ATO to pump water into your tank.

 

[link81]

RO units tend to be more efficient when they are allowed to run for a longer stretch.

i.e. running 20 min once a day to fill a reservoir is better then running 30 sec to top off a tank every hour.

 

[clm65]

Do you have space in the cabinet or next to the tank to add some sort of reservoir? You could run your rodi line to the res, and then add the additives you would like to add if there are any, then get a traditional ATO to pump water into your tank.

Nope, no real space for a reservoir. And I don't feel I am missing out by not being able to add anything to a reservoir. I have dosing pumps to use if needed, or I can set up a small container to drip anything into the sump if needed. I guess, at this point, I don't see a reason to get a traditional ATO, unless someone points out a fatal flaw in my system.

 

[dank reefer]

Nope, no real space for a reservoir. And I don't feel I am missing out by not being able to add anything to a reservoir. I have dosing pumps to use if needed, or I can set up a small container to drip anything into the sump if needed. I guess, at this point, I don't see a reason to get a traditional ATO, unless someone points out a fatal flaw in my system.

The only flaw I see is if your solenoid gets stuck in the open position.

Edited: Sorry - missed the Float valve portion of your post.

 

[clm65]

RO units tend to be more efficient when they are allowed to run for a longer stretch.

i.e. running 20 min once a day to fill a reservoir is better then running 30 sec to top off a tank every hour.

Well, that is good to hear, as the solenoid valve accomplished what you recommend!

 

[Iván Olalla]

If it has worked fine for you i dont see any issues, just check the float valve... If it was me i would put a solenoid which cuts the rodi line if a float valve is triggered with more fresh water than desired level in the sump...just a failsafe for peace of mind

 

[Silent]

You could get TDS creep with the on-off-on-off method you are using. Also what happens when your solenoid fails? You need to have a redundancy for that.

 

[WVNed]

If it's been working since 2000 why do you care what we think? I do lots of things different than most people.

 

[clm65]

The only flaw I see is if your solenoid gets stuck in the open position.

Yes, that is a potential problem. But it would also require a stuck open float valve to overfill the sump. Sure it can happen, but I think my odds are pretty good there. Also, not that it would help the tank, but the bottom of the tank enclosure has a shower liner and floor drain to keep from flooding the living area upstairs. Most of the overflowing water would drain outside, but a small amount would end up in the garage (found that out by experience ).

 

[clm65]

If it has worked fine for you i dont see any issues, just check the float valve... If it was me i would put a solenoid which cuts the rodi line if a float valve is triggered with more fresh water than desired level in the sump...just a failsafe for peace of mind

I like that idea!

 

[WVNed]

I have a reservoir with a float valve off my RODI. and an ATO system in the resevoir. If the float valve fails I get clean water on the floor instead of tank water. If the ATO fails on my sump will hold all the water. If it fails off the tank pump will start blowing air and I will notice.
This is how I minimized the risk to the best of my ability. You never get to 100%

 

[clm65]

You could get TDS creep with the on-off-on-off method you are using. Also what happens when your solenoid fails? You need to have a redundancy for that.

I do check the TDS meter periodically. I don't have terrible water to begin with, so it runs at 0 TDS for a very long time. The float valve provides redundancy if the solenoid valve fails open. There is no redundancy for a failed closed solenoid valve. I would eventually see bubbles when the return pump starts sucking air.

 

[clm65]

You could get TDS creep with the on-off-on-off method you are using. Also what happens when your solenoid fails? You need to have a redundancy for that.

I do check the TDS meter periodically. I don't have terrible water to begin with, so it runs at 0 TDS for a very long time. The float valve provides redundancy if the solenoid valve fails open. There is no redundancy for a failed closed solenoid valve. I would eventually see bubbles when the return pump starts sucking air.

 

[Silent]

You have a pretty solid method. Can it fail, yes but I think if you replaced the float valve and the solenoid regularly you should never have a problem unless it is TDS related.

 

[clm65]

If it's been working since 2000 why do you care what we think? I do lots of things different than most people.

Why do I care? I've been in this hobby for a long time, but there is still a lot that I don't know. And there a loads of people on this site that are much smarter than me. So when I'm doing something that seems contrary to what everyone else is doing, I figure it is worth at least asking what I might be missing. Doesn't mean I am going to change what I am doing, but I would like to at least understand where I might be vulnerable.

 

[Greybeard]

Nothing wrong with this system. My system is similar. RO/DI output to mechanical float valve in sump. 'Above Normal' water level sensor attached to Apex, alarms, and turns OFF output connected to electric ball valve. Ball valve closes when power is lost. I've added a 'high level' sensor as well, hard wired to an audible alarm, if the water level gets within an inch or so of the top of the sump, and a battery powered water alarm on the floor under the sump.

Works great, I sleep well at night.

On RO/DI system 'TDS Creep': Yes, RO membranes run more efficiently if you let them run for extended times. True, BUT... Water from that RO membrane is going through (in my case) a 3 stage DI system. No way that little bit of contaminate is getting into my tank. No. Way.

Add in the fact that my RO system is not used for tank alone... My RO system feeds a 5g pressure tank, attached to a drinking water faucet, fridge ice and water in the kitchen, and an ice maker on the patio. The RO unit runs a lot.

Also, you've got to do proper maintenance. I inspect my float valve, manually trip my 'above normal' sensor to insure it's working as expected, weekly. I replace my sediment filter, flush my RO membrane, and inspect my color change DI cartridges monthly, and change my (4) carbon block filters quarterly. RO membranes seem to last me about 2 years.

 

[mike550]

Truly armchair plumbing here. But wondering if you could fill one of those 2.5-5G pressurized tanks that they use for household RO systems with RODI, and use that to feed the tank. Your RODI could run for longer periods of time to fill the tank, and you’d still get the effect you desire.

 

[TinCanHero]

my 2 cents is if it ain't broke don't fix it.. if this has been running for 20 years almost leave it alone

As for the downsides, as people have said there are only a few, on-offing isn't the best method and because its a direct link to the mains if both the solenoid and float valve failed it would suck. if it where I and you wanted to upgrade id just add a RODI tank in the middle and have your RODI system come on for a few hours every few days instead.

Kind regards, TinCanHero.

 

[45ZoaGarden]

Only downfall is a potential float valve failure. You could add optical sensors to make it more secure if you wanted. You could always add a three way splitter to the output hose in your garage and add a ball valve and run that line to a bucket if you wanted to test your water. I would add optical sensors just in case. You can never have too many security blankets. But there is no reason for you to spend $200 and get a conventional system. A $20 sensor and id say you’re good.