Good Out Put Reading On RO\DI Unit
- Thread starter tcarroll
- Start date
RyanG
Reef enthusiast
I would expect less than that 5-10ppm or less IMO. Are those reading from RO only or is the water going through the DIO filter?
Piggy
Reef enthusiast
I get a zero reading. I've had it for awhile now. Not really sure what a safe level is.
A good RO membrane should reduce the original TDS reading by around 95 percent, and a DI following the RO should get the reduction down by 99.99 percent, basically to zero. The industry recommendations for the replacement of the RO membranes is way off for reef tank usage though. The RO membrane manafacturers recommends the membranes be replaced when they remove less than 70 percent of the original TDS. I would suggest they be replaced when they can no longer remove 85 percent or more of the original TDS without the DI filters being used. Even then that 15 percent TDS is putting a heavy load on the DI filters. Any newly installed RO membrane that can not provide that level of TDS removal is either defective or is being fed water at too low a pressure. Generally the membrane is defective as they have a limited storage shelf lives and the retailers and suppliers ship the old inventory before the new. When the pressure is too low generally they just work inefficiently, but still lower the TDS to acceptable levels. The best way to insure long membrane life is to use adequate prefiltration of water, especially carbon filtration, and use the filter often. It should be used at least once a week, other wise it fowls with a bacteriological film. Never run a RO membrane with out prefiltering with a regularly changed carbon filter. Chlorine eats up the materials used to make most commonly used RO membranes, how quickly depends on the type. Acetate membranes will go bad in a matter of hours when used with chlorinated water that does not have the chlorine removed by carbon filtration.
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Bifferwine
I am a girl
Just RO should reduce TDS by 95%, RODI should reduce it by 99 to 100%. Each time you start up your RODI unit, let it run for a minute or two. I am planning on changing my membranes once the TDS gets above 10, anything below that is good quality water (where I live, the LFS sells RODI water with 50 or less TDS, that's how crappy the water is here).
Altohombre
The Tennis Pro Reefer
you are supposed to let the first couple of gallons run out first and then after you should be getting close to 0.
Most RO units list their maximum capacity for water input at 250 ppm calcium. They will remove much more than this, but at a lower efficiency and with increased wear to the membrane. Commercial producers of RO water in areas of high calcium are recommended to use ionic exchange water softeners before RO filtration, however few do, so the TDS levels are higher for filtered water as the membranes are damaged quickly by the higher levels of calcium. This is typically the reason that commercial suppliers of RO water supply water with higher TDS than comes from a home RO unit. The calcium is actually physically forced through the membranes causing tearing in the RO membrane. The water in commercial RO filters is run through at water pressures of 200 to 225 psi. The membranes also tend to clog with calcium. The same problems occur in a home RO filter membrane but to a much lessor extent due to the much lower water pressures used.
