help IDing an RO/DI

[blurry]

I ended up with a seconds RO/DI unit and was wondering if anyone could Identify it. previous owner said it was 3 months old, not sure of the brand though. I read 0 TDS from it, just wondering who makes it. thanks!

 

[ficklefins]

Does not look like it is from a company, but more of a home made creation from several vendors (reef and not reef). You don't see taste and odor removal on a lot of the reef-centric RO/DI units.

 

[AZDesertRat]

There are a million different companies that stick some off the shelf components together and sell them.
It really doesn't manke any difference who assembled it as long as it uses standard 10" replacement filters and a name brand RO membrane.
If you are using it for reef water, get rid of the horizontal GAC tast and odor filter as it adds TDS back in to the treated water and has no purpose for RO/DI. I would also drop back to a single 0.6 micron Chlorine Guzzler carbon block and turn the extra vertical canister into a full size DI for better perfromance and longer life. All it takes is a couple minutes time, maybe $5-6 in parts and a refillable cartridge of bulk DI resin. Much cheaper to replace and it will work much better with a full 20 oz of resin in a vertical bottom up flow pattern.

You might want to do some troubleshooting to find out the membrane condition before spending much money though. Take your tap water TDS, RO only TDS before DI and final RO/DI TDS to see the condition of the membrane.

 

[meisen]

Just to follow up AZDesertRat's informative post , IME a good quality membrane that is still working properly should throw less than 20 TDS (this will vary slightly with source water). With the DI it should be <5 ppm, most quality functioning systems will be at 0.

 

[AZDesertRat]

You really can't put a TDS number to a properly functioning RO membrane. You can say it should be removing 96-98% of the incoming TDS though. 20 is extremely high in almost all situations, that would mean the incoming TDS is in the 500-1000 range or higher. My incoming TDS is 830 and my RO only TDS is 5 to 6 depending on the pressure and temperature that day.
Test your tap water TDS and your RO TDS, those alone will tell you the rejection rate or removal efficiency. neither I or anyone else can give you a number it should be at or under unless we know your tap water TDS.

One thing to watch out for is may drinking water units, which it appears to be what that one was assembled for, use 100 GPD Dow Filmtec nano filters which are only 90% rejection rate new so TDS may be higher than with a 98% rejection rate 75 GPD RO membrane. Most vendors will try to talk you out of a 100 GPD Dow if they are doing their job and know anything about reef systems.

The DI TDS should be 0 period. Anything other than 0 is an indicator the resin is nearing exhaustion and iss releasing weakly ionized substances like nitrates, silicates and phosphates. Change your DI at the first signs of anything other than 0 TDS on a regular basis. Weakly ionized substances may not register well on a hobbysist grade TDS meter so its almost guaranteed you are passing them even though they don't show up as TDS.