finally got an ro/di unit. can i just put the water straight in?

[Blakeup295]

finally got an ro/di unit. can i just put the water straight in?

or do i need to use water conditioner like normal??

[stevek480]

Straight into the tank. You may have to run it 10-30 minutes the first use though, if the instructions say that.

[rayn]

Make sure you let it run and clean out the filters and membrane before using the water. However long the instructions say to. Also make sure you are running enough pressure through it, if not you can ruin your membrane and or go through DI like crazy.

[Blakeup295]

its a used one so it doesn't have instructions and already ran at least way longer then 30 min

[stevek480]

If it's used you may want to get a TDS meter to check that it is 0 and the filters are good.

[neoalchemist74]

+1 on tds meter 20 bucks at a grow store.
But yes you can use it right away

[Blakeup295]

it came with a meter so i guess ive been using 25 ppm before the ro di unit was 25 high or low for tap???

and its 0 ppm after

[RocketSurgeon]

As long as it is 0 after it's all said and done, you are good to go.

my tap water is around 160.

[aleonn]

When I got my RO/DI, I was instructed to run it for 1 hr in order to rinse the membrane and cartridges. During that time I double checked the pressure (ended up needing to get a booster pump since my water main pressure was too low), check for leaks, and as you've already done, check the TDS meter. 25ppm for tap isn't too bad.

[Blakeup295]

o wow so in general 25 wasn't that bad?

yeah im happy i got one anyway 0 cant be beat :P

[aleonn]

0 is always the best as I've learned the hard way

[Mavrk]

25 ppm is pretty good for tap (still would want 0 for a tank). You should test the water coming out of the RO before it goes to the DI. This will tell you if the filters need replacing. Unless the DI is used up, you should always get 0 out of the final end.

I believe it was AZDesertRat that said you should change the prefilters every 6 months no matter what the reading. This will protect the membrane. I'll have to find the discussion.

Edit: here is the post (I was close in my above post)
http://www.reefcentral.com/forums/sh...php?p=12794170

Prefilters and carbons have very little to absolutely nothing to do with final TDS. They are there to protect the RO membrane by screening out TSS or Total Suspended Solids, large particles and chlorine. The membrane and DI cartridge take out the TDS or Total Dissolved Solids, small stuff.

Change your prefilter and carbon block every 6 months like clockwork, these are what protects the expensive RO membrane. When you change them disinfect the housings at the same time to reduce or eliminate the risk of bacteria and virus growth in the filters.
Change the DI resin when you first start seeing signs of anything other than 0 TDS.
Change the RO membrane when you see a reduction in efficiency, if yours is a 75 GPD membrane you should be seeing a 96-98% reduction in TDS from the tap water reading with RO only. When it starts to go up after RO only that tells you the membrane is failing. 3 years is a normal life if you keep up with the filter replacements. 7-8 years or more is not unheard of, if you use premium filters like the 0.2 or 0.5 micron absolute rated prefilters and a 20,000 gallon carbon block.

[Buckeye Hydro]

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the useable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.

Regarding your RO membrane and DI resin, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in three places:
1. Tap water
2. After the RO but before the DI
3. After the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (ppm). Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter (collectively called “prefilters”) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less purified water (aka “permeate”), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependant upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the total dissolved solids (TDS) in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce less water as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal!

Russ