RO/DI poll re: pressure cannister

[letsgofishin]

ok, figured it out i guess...

this is to find out who has a pressure cannister on thier RO/DI filter, and how you are using it.

some have it inline with thier REEF PRODUCTION water, (not truley reccomended)
some have it tee'd off to only store 'drinking water', or for ice makers
some dont know?

thanks


s

 

[ReefMeister2]

This is an article/post that I did a number of years ago.

"RO/DI for Dummies"
http://reefcentral.com/forums/showthread.php?t=619925&highlight=RO/DI+Dummies

The only mistake to the thread (which was corrected in later posts) is that the final DI water should never come into contact with metal after the DI stage...the reason being that DI water is extremely "hungry" for minerals and will hence corrode metal parts in short order. The problem with storing DI water in bladder tanks is that they do have some metal components in the neck portion that does come into contact with the DI water.

Drinking water (regular RO only) is perfectly fine and is in fact what the bladder tanks are designed for. So, simply plumb your bladder tank to take in water immediately after the RO membrane and then to a faucet or fridge. As for DI water, You can then store the RO/DI water in any plastic/composite barrel.

This is where you'll want to mount a float switch (in the plastic barrel) so that everything is automated and water will turn off automatically once the barrel is full (assuming your unit has a ASOV installed, which most do). The link above has many pictures imbedded in the thread for you to look at and get ideas for your own installation, so........good luck!

(EDIT)
I see there is another thread going that goes into much more detail on the subject, AND from the experts in the industry. So check it out here: http://reefcentral.com/forums/showthread.php?t=2007943

 

[letsgofishin]

i saw that thread which is why i started this one...

seems that a pressure cylander shouldnt be used before the di resin either , which is why i started this poll..

I love having 3 gallons of ro/di water on demand... i dont want to wait to fill up a plastic bin.. and if i do, i am sure the water will get 'contaminated' while the bin is being filled...

so, damned if i do and damned if i dont...

 

[letsgofishin]

for the member who isnt sure? do you get drinking water from your filter? do you have a pressure cannister?

 

[ReefMeister2]

i saw that thread which is why i started this one...

seems that a pressure cylander shouldnt be used before the di resin either , which is why i started this poll..

I love having 3 gallons of ro/di water on demand... i dont want to wait to fill up a plastic bin.. and if i do, i am sure the water will get 'contaminated' while the bin is being filled...

so, damned if i do and damned if i dont...

This was my point as well. I too like to have DI on demand and was wondering just how much of a deal it is using a bladder tank to supply water to the DI. I'm sure the rise in TDS while in the bladder tank is not that significant enough to worry about as long as you don't mind replenishing the DI a little more often. To me its worth it as I'm not going to squabble over $10 worth of extra DI resin

 

[Buckeye Hydro]

ReefM - still seems to be some confusion re the TDS of the water in the pressure tank. Its not that the water "picks up TDS inside the tank."

RO membranes function because the pressure on the feedwater side is significantly higher than the pressure on the low pressure (RO output, or permeate) side of the system. The higher the difference in pressure on the two sides, the higher the "Net Driving Pressure" (NDP), the better the membrane functions, the lower the TDS of the permeate, and the longer the life span of the DI resin.

Now, if you install a pressure tank incorrectly on an RODI system, the back pressure from the tank decreases the NDP, and the TDS of the RO water will climb and shorten the life span of the DI resin.

This issue isn't a big deal with a drinking water system, as maximizing rejection isn't critical for RO drinking water. But on an RODI system, that's another story.

This is just one of the many ways that RODI systems vary between vendors, and one of the things that just makes us shake our heads when we hear people say "All those RODI systems are alike." They may look similar to someone not familiar with the technology, but they absolutely are not "all alike."

Russ

Russ

 

[Buckeye Hydro]

So if you happen to own one of the misconfigured systems - What to do?

We can walk folks through a low cost retrofit.

Russ
513-312-2343

 

[ReefMeister2]

RO membranes function because the pressure on the feedwater side is significantly higher than the pressure on the low pressure (RO output, or permeate) side of the system. The higher the difference in pressure on the two sides, the higher the "Net Driving Pressure" (NDP), the better the membrane functions, the lower the TDS of the permeate, and the longer the life span of the DI resin.

Now, if you install a pressure tank incorrectly on an RODI system, the back pressure from the tank decreases the NDP, and the TDS of the RO water will climb and shorten the life span of the DI resin.

Russ

Russ

AHHHH (light goes on in head) now THAT makes perfect sense to me....
Its just never been explained that way (at least not that I've read yet)

I always assumed that a 98% rejection rate membrane is going to produce 98% water under all (within reason) conditions. The back pressue issue however is obviously a factor counter productive to that goal.

(slaps side of head with carp) THANK YOU for the final clarification


Fortunately I now have two separate systems: one dedicated to producting DI water for reef tank (with NO pressure tank) and a separate unit to produce drinking water for the house (with pressure tank)
However I did have one of those home/reef combo units recently.


On a subject that is somewhat related.
What is the deal with those 150gpd membranes that claim still a 98% rejection rate? (ie: Ultratech TW1812-150 or Filmtech BFS-271) This just sounds too good to be true. (why would anyone purchase the 75gpd membranes if this were the case) There must be a consequence/trade-off somewhere, because price is really not that much more at $10-15 additional.

 

[Sisterlimonpot]

I'm the same way, I use a separate RODI for the fish tank (which doesn't have a pressure canister) and I have another RO system under the sink (that does have a pressure canister) strictly for drinking water.

 

[Buckeye Hydro]

Fortunately I now have two separate systems: one dedicated to producting DI water for reef tank (with NO pressure tank) and a separate unit to produce drinking water for the house (with pressure tank)
However I did have one of those home/reef combo units recently.

It IS possible to have a RODI system with a pressure tank that produces RO for drinking and DI for your tank, without having the water from the tank hit your DI (e.g., our Reef/Residential Series Systems). But the plumbing necessary to make it work correctly is not something you're likely to see on the cut rate ebay systems.

What is the deal with those 150gpd membranes that claim still a 98% rejection rate? (ie: Ultratech TW1812-150 or Filmtech BFS-271) This just sounds too good to be true. (why would anyone purchase the 75gpd membranes if this were the case) There must be a consequence/trade-off somewhere, because price is really not that much more at $10-15 additional.

This should help explain things: