Ro pressure tank as auto topoff??

Do not store RO/DI in a bladder tank, the DI is corrosive and will leach chemicals out of the rubber bladder as well as eat the metal in the tank.

 

Ok thanks for the added info when I found out filling the tank was bad for my ro membrane I decided not to go this route.

 

Salty,

I have my ATO, running off my RO/DI system.

I ran a long 1/4 tubing from under my kitchen sink (where my ro/di is ), thru the basement ceiling, and to the float valve on my sump.

My RO only feeds my drinking water faucet on my kitchen sink, and also T's off to the water in my frig for the drinking water in the door, and the ice maker!

Here's my thread with some pics. It's been working for a long time, no mishaps.
I did get a good qualty float valve off e-bay, about $14, not the cheap ones.

Oh, I didn't see Az's post.

Both my RO, and RO/DI are 0 TDS. Corrosive?

http://www.3reef.com/forums/i-made/todds-diy-ato-133471.html

In short, I think yes, you can do it, a tank like that is what runs the pressure thru my DI resin, after the RO.
Are you going to have the RO, or RO /DI feeding the tank?

Have you tested the TDS of your tap water? The phosphates and nitrates?

 

There are many articles about RO/DI being very agressive, it is constantly trying to get back to its natural "dirty" state so attracts anything it can to add TDS back.

No, it is not a good idea.

The other bad thing is using float valves or even bladder tanks causes the system to cycle on and off frequently leading to excessive TDS creep. Short runs are hard on a membrane versus longer less frequent runs which allow the membrane to flush itself of the accumulated solids.
Been doing this a long long time and can talk on the subject for days.

You always want to separate the DI feed so it comes straight from the RO membrane, not a pressure tank as shown in this drawing. The tee and check valve isolate the DI so TDS creep water in the pressure tank cannot find its way back to the DI:
http://www.spectrapure.com/huds/4-STAGE-DWK-RODI-NAG.pdf

I tried to use a pressure tank to store RO/DI myself many many years ago and it was not successful. I later tried storing RO only in a pressure tank but the TDS creep was excessive in the 5G pressure tank due to frequent cycling so I added a second tank to reduce cycles. It helped but still was not acceptable so I later installed a 14G pressure tank which held about 10 gallons when full and was better but still not acceptable and ate DI resin rapidly so I learned to follow this drawing the hard way.

 

+1 on this.

That's why it's best practice to disconnect your RO line from your DI resin and run it for 4-5 minutes before reconnecting to the DI. When an RO first starts, the "clean" water is actually very high in dissolved solids. It takes a few minutes for the fresh feed to flush the permeate side of the membrane and start rejecting dissolved solids. If you don't disconnect it, there is a period of time when you first start your RODI where the DI resin has to work extra hard to handle the high dissolved solids.

 

TDS creep should pass in 30 seconds to a minute depending on you system and water conditions. An easier way to accomplish this TDS creep flush is to install a DI bypass valve, its as simple as a tee and ball valve if you make water manually.
Spectrapure recently started selling automatic flush systems for this purpose If you make water automatically as many of us do. I believe a few other vendors offer something similar too.

 

Yep, that works too. I like the by-pass idea.

I like to go a little longer to make sure I've passed a few membrane chamber volumes through and fully flushed, but I agree that most of the flush is complete after a minute or so.

 

Buckeye Field Supply Premium units come with the DI bypass valve standard. Its a good thing to have for several reasons, for one it allows you to use RO only water for things like drinking and cooking and it also gives you a point where you can draw RO only water for testing with your handheld TDS meter.

 

I just have a three way valve on my membrane out put one tees into the drain line the other to the di. So if I flush my membrane TDS creep is not a problem correct? I do use a float valve and only produce 15 gallons 2x a week

 

You are correct. Sounds like a good set up.