RO storage question

[MJAnderson]

I want to set up an RO storage unit with a feed from my RODI.

I know that best practice is to not have your RODI refill your top off container constantly as TDS from the first small amount of water produced is often high. How do you set it up so that it only produces a minimum of a few gallons at a time and isn't running constantly due to evaporation?

 

[Jeff Trout]

Put it on a timer.

 

[serpentman]

<a href=showthread.php?s=&postid=13183463#post13183463 target=_blank>Originally posted</a> by Jeff Trout
Put it on a timer.

Ditto on that. I need to get one as I don't want my RO unit running while my softenerS are regenerating (~1am). Up until now, I manually run it when my reservoir is 1/2 full. There is a float switch to prevent overfilling as I almost always forget to shut it off when its full.

 

[Burgman]

MJ said:
I know that best practice is to not have your RODI refill your top off container constantly as TDS from the first small amount of water produced is often high.

How does that happen? If then water is pushed through a membrane would it matter if it was first or last through?

Dave

 

[Akronviper]

<a href=showthread.php?s=&postid=13184022#post13184022 target=_blank>Originally posted</a> by Burgman
MJ said:
I know that best practice is to not have your RODI refill your top off container constantly as TDS from the first small amount of water produced is often high.

How does that happen? If then water is pushed through a membrane would it matter if it was first or last through?

Dave

I don't know how or why this happens but have found that it is true. After a few months my stored RO water has a TDS of 40 due to TDS accumilation. Now I let run for 5 minutes before any filling of my RO container and have been at 0 TDS since.

I would fill a separate container and use a small pump on a timer or float valve to top off and would check your storage containers TDS randomly.

 

[carman9941]

I think the tds is leached from the di resins

 

[MJAnderson]

<a href=showthread.php?s=&postid=13184022#post13184022 target=_blank>Originally posted</a> by Burgman
MJ said:
I know that best practice is to not have your RODI refill your top off container constantly as TDS from the first small amount of water produced is often high.

How does that happen? If then water is pushed through a membrane would it matter if it was first or last through?

Dave

My understanding is that it leeches back into the water sitting into the RO unit. Not that it's a huge amount, but if you have the RO on a float valve in a small container where it's only making a few cups of water at a time you will just be pushing out the water from inside the RO/DI resin which will have higher TDS. If you make a gallon, it's diluted so you never notice.

How do you put it on a timer? I want to hook it into my water supply and run it directly into a reservoir. No pumps involved, just a float valve.

 

[CleveYank]

Solenoid?


As in solenoid valve hooked to timer or low level sensor?

I cannot recall where I saw it. But someone...tank of the month winner mentioned something like that to counter the TDS issues from the small batching of RO/DI production. Sorry I can't recall who or where.

 

[itZme]

It's called "TDS creep". The first few quarts of water produced will have higher TDS and then it will drop down to zero or close to it. There are a couple ways to do it. You could use a solenoid like the guys have said above or you could use an "anti-TDS-creep" device that keeps your float valve up until the storage level reaches a certain point lower in the storage bin. I have seen a couple of people make a tower that holds water until the storage level reaches the bottom of the tower in order to break the seal and then the water rushes out of the tower to lower the float switch and begin the refill process. This way the water level could go from the top of your reservoir to nearly the bottom and then refill again in one shot.

It uses the same theory as those self-watering pet dishes or the 5gal office water coolers. Just like you can turn an glass upside down and pull it out of the water backwards and it stays full of water until the rim breaks the surface.

I will try to find the thread I saw but it was at least a year ago. Air, Water, Ice has an Anti-TDS creep RO storage tank they sell HERE

Here is a DIY device

YAY! Found it http://reefcentral.com/forums/showthread.php?s=&threadid=275455


-- Kevin

 

[Jeff Trout]

They sell digital or manual timers at wal-mart for lawn sprinklers.
It would shut the feed water off which would also stop the waste.