How to achieve ZERO TDS? ? ?

[allan_mark76]

Hey guys quick question - How do you achieve zero tds via RO. I have a 3-stage RO unit with a 5micron sediment filter, carbon, and 100GPD membrane. I just recently added a permeate pump and I can't seem to achieve anything lower than 100tds. I was wondering if it was the addition of a permeate pump. It's killing me as my breeding water is all messed up. Anyways if anybody has any thoughts please let me know. When I swaped everything out I was good and now it's all over the place.

Also will adding a DI block help?

Thanks.

~AKA~:antlers:

[yim11]

I have the same setup + DI and - perm pump...my RO is at 0 tds unless my filters start to get old. You sure whatever you are using to measure the water with is accurate?

HTHs,
-jim

[Chad Hughes]

Permeate pumps are supposed to only work with pressurized vessels. I have a 4 stage and I use a boost pump to bump my pressure form 60 to 110 PSI. I make more water faster that way. I'd pull that pump off and check you production values. Did you change anything else other than the pump?

I get 19 ppm out of filters that are over a year old and have produced about 800 gallons of RO weekly.

Best wishes!

[lkevin]

I think adding a DI after the membrane will help. Even without it, 100ppm is pretty high for a functioning RO unit. People I know replace the membrane once it gets into the 50-60 ppm range.

Maybe the pump is pushing the water too quickly through the membrane and not giving it enough time in contact. That, or your membrane might need replacing.

Just a side note, I think it is important to keep the sediment and carbon filters fresh, since they protect the membrane and prevent it from getting burned out faster.

Hope this helps,

Kevin

[DHavens]

#1 You need to know where your starting from...
#2 I use a water softener for the whole house and get a 0 tds with a used 8 year old membrane.
#3 Measure the cost of the DI resin against the cost of the RO membrane....You might find that the cost of the resin will gain you a lot more time with the membrane.
Resin is cheap compared to the cost of the RO membrane....and it can take the "Hit" of all the crap in the water before it gets to the membrane.

and last but the most important....GET A RO FLUSH KIT!!!!....it helps with the life of the RO....I made mine and I'm going on 9 years...and it was used when I got it.

PS... I'm also a reef keeper so 0 TDS means more to me than anything else

[Don Trinko]

Most TDS meters are calibrated at only one point soI'm not sure that even if it read zero it realy would be. Also Fish can not live in zero TDS so your going to have to add something anyway. All IMO; Don T.

[Daniella]

where do you get this flush kit?

when my RO-DI unit was brand new, I had readings of 0. Now it's 3, after 6 months.




#1 You need to know where your starting from...
#2 I use a water softener for the whole house and get a 0 tds with a used 8 year old membrane.
#3 Measure the cost of the DI resin against the cost of the RO membrane....You might find that the cost of the resin will gain you a lot more time with the membrane.
Resin is cheap compared to the cost of the RO membrane....and it can take the "Hit" of all the crap in the water before it gets to the membrane.

and last but the most important....GET A RO FLUSH KIT!!!!....it helps with the life of the RO....I made mine and I'm going on 9 years...and it was used when I got it.

PS... I'm also a reef keeper so 0 TDS means more to me than anything else

[Apistomaster]

Something must be wrong. Perhaps you are using too much pressure as was suggested, or perhaps your meter is providing a spurious reading? I have been using a 60 gpd Maxxima HI-S unit on the original membrane for almost 4 years without the mixed bed ion exchange cartridge and my product water is no higher than 10 ppm TDS. It sounds like you have too much source water somehow by passing the membrane for some reason providing your readings are correct.

A 0.0 TDS is of no practical value for keeping fish since the water mineral content must be reconstituted to whatever range your fish need but no fish can live in absolutely ion free water.

I happen to raise my TDS to about 50 ppm for my fancy pleco and wild Discus breeding tanks.
Very few fish need a lower value. Maybe cardinal or Rummy nose tetras may need only about 25 ppm TDS to get good egg hatches but these are exceptions.

I have successfully bred wild Blue/Brown Discus in water with a TDS as high as 450 ppm so that demonstrates how adaptable they are. Most domestic strains of Discus can breed and yield good hatches in water with 200 to 450 ppm TDS. If I have any problems with good hatches from domestic Discus I may use water with a TDS of 75 to 100 ppm TDS. This has sometimes made a difference with some pairs of some strains.

I would concentrate on troubleshooting why your RO unit is apparently malfunctioning.
I tried to install the membrane back flush system on my RO unit but I couldn't get my kit to work. Since my product water continues to produce satisfactory water for as long as it has and I will have gotten plenty of use and expect at least another year or two I will probably just replace the membrane. Actually my plans are to buy a higher producing unit able to produce at least 200 to 300 gpd so it will refill my 110 gal RO storage reservoirs much faster.

One thing I do is to replace the initial particulate filter about every 6 months and the carbon block annually. I use about 200 gal of RO water each week.
My source water only has 340 ppm TDS which isn't very high so that helps get more lfe out of the membrane than if the TDS was much higher.

[evallarta1]

If you want your readings at zero you need to add a DI unit. But like everyone else said you dont want a zero reading UNLESS you are doing a saltwater tank (nutrients are added through the salts). How old are your filters? Depending on your water and age of your filters you may have to replace your sediment and carbon filters.

[Daniella]

And even a DI does not last much than 3 months then it will start to show some readings. Not a lot but still not 0.


If you want your readings at zero you need to add a DI unit. But like everyone else said you dont want a zero reading UNLESS you are doing a saltwater tank (nutrients are added through the salts). How old are your filters? Depending on your water and age of your filters you may have to replace your sediment and carbon filters.