New to RODI

[PFoster]

Originally Posted by gregzz4

I'm finally making water with a 100gpd RODI unit
My questions are;
-do I need a powerhead in the storage tank
-is there any point in a heater for the storage tank as it's in a heated room

I think you are in good hands with the other questions so I will add a bit to these.

You do not need a power head in your storage bin BUT if you add one (or better yet an air pump) if will bring up the pH of your fresh salt water before you add it to your system.
Test the pH of your freshly mixed sw, I can pretty much guarentee that the pH is low and this is done intentionally by the manufacturers as the lower pH allows the salt to mix faster.

As for a heater again its not required but it would help reduce the swings when you do your water changes.

The more stable your system is, the better your corals will look.

[gregzz4]

Thanks P
I have heaters and powerheads for my ATO and New Saltwater holding tanks, so no concern there about variances.
About the pH in the storage drum... that rings a bell, but I don't recall what I read. I'll have to look around today about that as I want to know how that happens.

[gregzz4]

I've been messin' around with the flush valve on the RO unit. I've found that I can totally shut off the waste water line, and then I get nearly 100gpd, based on some math.
I think I'll run it around 80gpd and flush it every couple of hours.
Otherwise, if I use the valve in it's normal position, I only get about 40gpd, with a lot of waste. No point wasting all that water with the incoming TDS @ only 7-8ppm.

[hillegom]

Did you install a flow restrictor in the line? If the correct one is in there, you will get 100gpd with 400 gal waste. The flush valve should only be used to back flush the membrane, otherwise it should be shut off.
If you do not get 100gpd form a 100gpd membrane, then either your feed water pressure is too low, or the temp of incoming water is too cold.
I don't have a flush valve, the last membrane lasted 3 yrs. I have been debating whether I should instal one, but some co. speak against flushing.
So until I can research more, I won't backflush.

[gregzz4]

Ya, I've been debating the whole idea of playing with the valve. With it completely closed, I'm not getting 100gpd.
I think I'll get a restrictor as this unit didn't come with one, neither inline nor in the output elbow.
Thanks again

[hillegom]

Very unusual not to have a restrictor, it creates the proper backpressure so water gets fed through the membrane. I wonder if it already comes with one installed. Some restrictors are inside of the quarter inch black poly tube. It should be right at the connection where the black tube comes out of the ro membrane canister. It will look like this:
http://www.marinedepot.com/Flow_Rest...RORAFR-vi.html
And is pushed into the black tube so only the shoulder is sticking out. Mine is coloured black and its hard to see unless youknow its there.

[gregzz4]

It was definately missing. I checked all the packaging and the white tubing that came with this unit.
I just got back from J&L and there is now a 100gpd in the black line leaving the RO membrane.
I'll report back once I do some more math.
And once again, Thanks hillegom, you may have solved another issue for me
Down the road I'll change over to the inline style when I go with a 75GPD membrane. I've heard the 75s are more efficient.

[Buckeye Field Supply]

A 75 gpd membrane with a proper flow restrictor will still produce apx. 4 parts waste water to 1 part purified water, so it's no more "efficient" in this regard.

What a 75 will do much better however, is clean the water. Here are some spec's for you (the 24 - 100 gpd membranes are Filmtec brand):



Russ

[gregzz4]

Thanks for that Russ. I don't believe Vertex's claims of 98% rejection on the 100gpd I bought, but with 8ppm in and 0ppm out, guess it doesn't matter anyway. Makes me wonder if I'll ever need the DI.

[mike31154]

On the other side of the coin, if your source TDS is consistently that low, you could simply run it straight through DI only, ditch the RO membrane altogether. Water production may be a lot quicker in that case, although not sure if contact time going thru DI is a factor, probably is. Don't necessarily recommend you do this, but I always like to look at things from a different angle. With an oversized cartridge full of DI media, or even a number of standard DI cartridges in series, you could probably get a good amount of 0 TDS water for your tank before the DI is depleted.