RODI hook up

Branespikin · Apr 12, 2016

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RODI hookup question
I am planning on teeing off my RODI to a freshwater container (7Gallon)and one to a saltwater container also 7g. The FW will be in one of my kitchen cabinets and the SW will be under my cabinet by my sump. My question is i want to install float valves on both containers so when they are full it can trigger the auto shutoof in my RODI unit so if one container fills and triggers the float valve will it shut off the wster supply to the other container? Or will it continue to fill into other container and when both containers are full and floats are up then the auto shut off will kick in on the RODI?

120reefkeeper · Apr 12, 2016

Yes they will work independently of each other. If both need water then they will both get water. If one needs it then it will receive it. The auto shutoff will occur when both shutoffs are closed ... "Full"

twilliard · Apr 12, 2016

There may be an issue with TDS creep depending on how the water is used.

120reefkeeper · Apr 12, 2016

I agree with twilliard. Running such small batches will negatively effect TDS and is really hard on the filters. It is much better to run large batches of water.

What your suggesting will technically work, but those are some downsides of doing it.

Squadir · Apr 12, 2016

120reefkeeper said:
I agree with twilliard. Running such small batches will negatively effect TDS and is really hard on the filters. It is much better to run large batches of water.

What your suggesting will technically work, but those are some downsides of doing it.

Not to hijack he thread but if he was to do larger batches wouldn't the same thing happen when the filters are just sitting there with water in them and not being used?
Just asking because I'm going to hook up a unit soon and was wondering about this same thing.

AZDesertRat · Apr 12, 2016

When you make larger batches of water it cleanses the membrane better and minimizes the effect of TDS creep. When the RO starts and stops frequently you get a spurt of TDS creep in the finished water every time so TDS accumulates.

Bdog4u2 · Apr 12, 2016

If the di cartridge is after the membrane wouldn't it pick up the slack.

120reefkeeper · Apr 12, 2016

Bdog4u2 said:
If the di cartridge is after the membrane wouldn't it pick up the slack.

Yes it will for a time , but you'll be burning through resin like crazy and unnecessarily.

Branespikin · Apr 12, 2016

Thx for the input! I have a 65g tank so im assuming the 7g resevoir for FW will last me 7-10 days maybe. The SW will be hooked to my neptune Dos and will be doing an automatic water change maybe 1/2 gallon a day so thats 2 weeks of water in there. When both reservoirs are full i will manually turn off my Rodi unit with a ball valve so it wont be in use for lets say about a week till the FW is about almost empty. Then i will open the valve to let both refill and add salt to th SW tank accordingly and repeat. So its not like the RODI unit will be going on and off the whole time. Probably every week it would make a new batch of 12 gallons of fresh water.

120reefkeeper · Apr 12, 2016

Squadir said:
Not to hijack he thread but if he was to do larger batches wouldn't the same thing happen when the filters are just sitting there with water in them and not being used?
Just asking because I'm going to hook up a unit soon and was wondering about this same thing.

I personally flush my filters for 2 minutes before I make a batch and for 2 minutes after I'm done. Is it necessary?? I think it prolongs the membrane life.

I make make about 40 gallons at a time.

AZDesertRat · Apr 12, 2016

Flush kits do nothing for TDS creep, they are more a warm fuzzy feeling. Flush kits install on the waste line and when open slightly increase the waste flow, in theory this scours the waste side of the RO membrane but its not really enough to do much if anything.
TDS creep happens each time the RO is shut off, what happens is the treated water is agressively trying to get back to its natural "dirty" state so it osmoses or draws the TDS from the tap water side of the membrane until it equalizes on both sides.
TDS creep is on the treated side of the RO membrane, not the waste side so the flush kit doesn't do anything for that. You can install a DI bypass valve between the RO membrane and the DI filter though so when you make water manually you can open this valve and flush the first 30 seconds to a minute of TDS creep to the drain before closing the bypass valve and sending clean RO water to the DI so it lasts much longer. This only works if you make water manually and are there when the system starts. You can buy automated valves for this purpose but they are pretty pricey.