Is it better to keep RODI reservoir topped off or to use it all?

[Nardi]

I've been wondering what's better for maintaining the water quality in my 20 gallon barrel of RODI water.

I use it both to fill my 5 gallon water top off and to fill a 10 gallon bucket for water changes.

Haven't been able to find much on the subject. So do you guys use all the water first before refilling or top off what you used right away?

 

[Jimbo327]

I only run the RODI once per week. My reservoir is only 1/2 empty after 1 week. When I do run it, the barrel is refilled to the top and turned off. It is all automated by the APEX and floats.

 

[Randy Holmes-Farley]

The water itself doesn’t matter, but an ro/di is best run in larger batches due to what happens between uses: salt creep across the ro membrane. If you turn it on and off every day or two, salt equilibrates on each side and you need to remove that with the di. If you only run it once a month, you still have that, but only one batch of it instead of 15 or 30 of them.

 

[Nardi]

The water itself doesn’t matter, but an ro/di is best run in larger batches due to what happens between uses: salt creep across the ro membrane. If you turn it on and off every day or two, salt equilibrates on each side and you need to remove that with the di. If you only run it once a month, you still have that, but only one batch of it instead of 15 or 30 of them.

I run the rodi every other day with the flush valve open on the membrane. I thought that was the recommendation on the manual.

Edit - Never mind. I misunderstood. That makes sense, thanks!

 

[Randy Holmes-Farley]

I run the rodi every other day with the flush valve open on the membrane. I thought that was the recommendation on the manual.

If you flush the downstream side of the membrane every use, then that eliminates the concern, but most folks do not do that. I never once did it in 20 years.

 

[Nardi]

Gotcha. I just do it for a couple minutes when I'm doing laundry to get the tds to drop back down to about 5 then turn it off.