RO questions

[Myka]

I just got an AquaFX Barracuda 4-stage 50 gpd RO/DI unit. I have never had an RO or DI unit or any kind. I have been buying my RO water from the grocery store. So, I'm a newbie here trying to gather as much info about this piece of equipment as possible. I've been reading lots on RC and searching all over, but still have a few questions.

My unit is 50 gpd. Can I put a 75 gpd RO membrane in it when I replace it, and then it is suddenly a 75 gpd unit? Or is there more to that than just the membrane?

I have read that RO membrane that are over 75 gpd are less effective. Is that true?

I have a psi meter right on the unit. It reads 45 psi when I turn my tap on full blast (just cold). When that drops I should replace my sediment filter, right? How much can it drop before I should replace it?

My understanding is that the carbon block is usually changed at the same time as the sediment filter. I understand that the purpose of the carbon block is to remove chlorine as chlorine will damage the RO membrane. Is that right? So in order to know when it is time to replace the carbon block, I assume it may be wise to purchase a chlorine test kit and test the water coming out of the carbon block. Good idea?

How often and for how long do I use my flush kit? I haven't found a definitive answer for this.

Lastly, I really don't like all that waste water going down the drain. Considering the chlorine has been removed, is the waste water good for drinking water and for use as waterchanges on my freshwater tank?

[DarG]

I wouldnt use the waste water for anything but washing clothes or lawn watering. It isnt anything more than tap water with a little higher concentration of the stuff that we dont want in our tanks, but I dont want that little extra in my body and I dont want to taste it either, our tap water is nasty as it is. You may as well treat your fresh water fish to the good water since you bought a system.

Most membranse over 75 GPD arent as efficient, most 100 GPD membranes are around 92% or so while 75GPD are 98%. I think There is a higher GPD unit that is as efficient (or close) as the 75's but i dont recall who makes it.

You can go up to a 75 you just need to get a 75 gpd flow restrictor as well when you replace the membrane.

Pressure will increase when your filters get dirty and clog.

45 psi is low or atleast on the low end of ok for the ro membrane. Water production quantity will be lower and efficiency also drops when the pressure is too low. Check the minimum operating pressure of your membrane. I think that you may be borderline at 45 psi.

Im sure one of the ro experts will chime in and elaborate for you.

[Myka]

Originally posted by DarG I wouldnt use the waste water for anything but washing clothes or lawn watering. It isnt anything more than tap water with a little higher concentration of the stuff that we dont want in our tanks, but I dont want that little extra in my body and I dont want to taste it either, our tap water is nasty as it is. You may as well treat your fresh water fish to the good water since you bought a system.

Well, there is a lot of noise about RO water not being so good for our bodies. That is why you see a lot of bottled water that says it has minerals added. Check this out: http://watershed.net/purified.aspx I'm really not sure what I want to believe...but I figured the tap water can't be that bad. I dunno.

Oh, and I know that RO water isn't optimal for freshwater fish unless you add something like Kent Freshwater RO Right or something similar which will add salts, buffers, trace elements, etc. Our marine tanks have the salt mixes to do this for us.

Most membranse over 75 GPD arent as efficient, most 100 GPD membranes are around 92% or so while 75GPD are 98%. I think There is a higher GPD unit that is as efficient (or close) as the 75's but i dont recall who makes it.

You can go up to a 75 you just need to get a 75 gpd flow restrictor as well when you replace the membrane.

Pressure will increase when your filters get dirty and clog.

Ah, right I forgot about the flow restrictor. Hmmm...I might upgrade later on.

45 psi is low or atleast on the low end of ok for the ro membrane. Water production quantity will be lower and efficiency also drops when the pressure is too low. Check the minimum operating pressure of your membrane. I think that you may be borderline at 45 psi.

My unit says 35 psi minimum for the RO membrane.


Ooops!! Upon further inspection, my unit runs at 50 psi, not 45. I didn't look closely enough.

Thanks for your help!!!

[BuckeyeFS]

I just got a 4-stage 50 gpd RO/DI unit. Can I put a 75 gpd RO membrane in it when I replace it, and then it is suddenly a 75 gpd unit? Or is there more to that than just the membrane?

Assuming your system accepts stand-sized membranes, you can add a higher (or lower) capacity membrane very easily. Pull the old one out, slip a new one in, and flush the new membrane appropriately. You'll also need to replace your flow restrictor. Flow restrictors are matched to the capacity of the membrane, and serve to partially plug the waste line that exits the RO housing. By partially blocking flow in the waste line, they serve to pressurize the RO housing. It’s this pressure that allows the reverse osmosis process to work. So - all systems have flow restrictors.

There are three common types of flow restrictors. The plug-type restrictors are just that - a small plastic cap, or plug with a very small hole that is inserted in the waste line of the RO (sometimes these come inside the fitting at the waste port of the RO). To find this type of restrictor, remove the waste line from the waste port on the RO housing, and look INSIDE the tubing. Remove the restrictor and replace it with a restrictor sized appropriately for your new membrane.

Some systems use a capillary flow restrictor. These restrictors look similar to the plug type, except they have a long, thin (several inches to a foot or so) capillary tube extending from the cap. Again - this type of flow restrictor can be found INSIDE the waste tubing.

A third type, sometimes called block or tube restrictors, look like a short length of 1/2 –inch pvc tubing with a quick connect fitting on each end. Some of these restrictors have an integrated flush valve.

I have read that RO membrane that are over 75 gpd are less effective. Is that true?

Filmtec 50 gpd = 98% rejection rate
Filmtec 75 gpd = 98%
Filmtec 100 gpd = 90%
BFS 150 gpd = 98%


I have a psi meter right on the unit. It reads 45 psi when I turn my tap on full blast (just cold). When that drops I should replace my sediment filter, right? How much can it drop before I should replace it?

Your pressure, even with clean filters, is low. So I wouldn't think you'd want it to go any lower than 40 psi.

My understanding is that the carbon block is usually changed at the same time as the sediment filter. I understand that the purpose of the carbon block is to remove chlorine as chlorine will damage the RO membrane. Is that right?
In general, yes.

So in order to know when it is time to replace the carbon block, I assume it may be wise to purchase a chlorine test kit and test the water coming out of the carbon block. Good idea?
That would be an unusual approach. More standard approach would be to replace the block BEFORE you get chlorine break through - carbon blocks come with a specified chlorine capacity - change the clock when you get to about 75% of the chlorine capacity or a 6 months, whichever comes first.

How often and for how long do I use my flush kit? I haven't found a definitive answer for this. If you were in a lab setting you would use it ever time you shut the system down. That's not practical for most reefers, so once a week is better than once a month is better than once a year.

I really don't like all that waste water going down the drain. Considering the chlorine has been removed, is the waste water good for drinking water and for use as waterchanges on my freshwater tank? Potentially - remember that the tds in the waste water will be about 20% higher than in your tap water. If you have low tds to start with, it may be fine to drink. If you have high tds to start with, you may not like the flavor. You can use it for laundry, watering the plants, etc... You'll have to specifically look at the quality of the waste water to know if it is ok for your fresh water tanks.

Feel free to call if you have questions... my fingers are cramping!

Russ

[AZDesertRat]

Yes, you can replace the 50 GPD with a 75 GPD and a matched flow restrictor and you have a 75 GPD unit, that's all it takes.

A Dow Filmtec 100 GPD membrane is not as efficient as their 75. A 100 is actually a 90% efficient nanofilter membrane and not a 98% efficient Reverse Osmosis membrane. Big difference.

Dow Filmtec membranes will deliver their rated GPD at 50 psi and 77 degrees F water temperature. If either/or is less it will be slower. If either or both are higher it will deliver more, still at 98% efficiency. Always turn the cold water on all the way for best pressure and delivery rates. If you have normal tap water you may never see a drop in pressure. You WILL want to replace the prefilter and carbon block every 6 months regardless if pressure dropped or not. This is done for several reasons, one is the pressure drop across dirty filters, two is carbon will only adsorb the chlorine from so many gallons of water until it is exhausted and possibly ruins the RO membrane, and three is to reduce or eliminate the possibility or bacteria or virus growth inside the housings. Always disinfect the housings when replacing filters, you should have received directions on how to do this with your unit. If not they are posted here and a quick search will bring them up.

If you are using a good Matrix or Chlorine Guzzler type carbon block you do not have to worry about chlorine getting to the membrane. Matrix blocks in the 0.5-0.6 micron range are good for 20,000 gallons of water at 1 ppm chlorine residual. DO NOT use cheap carbon replacements, some are only good for as little as 300 gallons.

Flush kits are not a proven product. I have never owned one and always get 3+ years or more out of every RO membrane. The only way they can be of any value is if you flush for a few minutes EVERY TIME you are done making water. If you use it hit and miss then it is of no value at all since dissolved solids have begun to harden on the surface of the membrane already and cannot be removed no matter how much flushing you do. No one has ever shown proof that they do anything at all, I wouldn't sweat it. They are more a sales gimmick than anything.

They waste is fine for lots of uses depending on how bad you water is to begin with. A TDS meter will tell you this. You should have a good handheld TDS meter if you have an RO/DI unit, otherwise you have absolutely no idea if it is working or not or when to replace the DI resin or membrane.

The waste stream is going to be 20 to 25% higher in TDS than your tap water if the unit is working correctly at a 4 to 1 water ratio. The waste stream has been through a particulate filter and a carbon filter so it can be drank safely. I don't myself as I like the taste of RO water and use my RO only flow for cooking, drinking and ice maker among other things. Don't get hung up on waste, it all gets recycled anyway, we are not making any new water, it is the same water that has been on Earth for millions of years, no more no less. It will go either back into the ground, recharging the aquifer, on a golf course or any number of uses.

DarG was incorrect in his statement that pressure will go up when filters get dirty. Pressure available to the RO membrane will actually go down and flows will slow accordingly.

[BuckeyeFS]

To clear up a few things mentioned in posts above:

Your water pressure reaching the membrane will DECREASE when your prefilters clog.

If your water pressure drops any lower than 40 psi I can't see you being happy with the way it performs.

[DarG]

Originally posted by BuckeyeFS
To clear up a few things mentioned in posts above:

Your water pressure reaching the membrane will DECREASE when your prefilters clog.

If your water pressure drops any lower than 40 psi I can't see you being happy with the way it performs.

Thanks BFS and AZ ... for some reason I was thinking about the pressure in front of the pre-filters. Brain fade. And I do it every single time this comes up.

To the OP ... I didnt suggest you drink the RO. It's up to you whether you do that or not. I was suggesting that MY tap water tastes bad enough without being further concentrated with what makes it taste nasty in the first place so I wouldnt do it. You can if you like.

Using the waste water for your fresh water tanks also adds a higher concentration of all the things in your tap water that the RO pulls out. I used RO when I had fresh water tanks and added the RO-Right or whatever other conditioner I used at the time. But you can use it if you want to and drink it if you want to.

Personally, I only drink Distilled or Purified bottled water. Thats all I have been drinking for the last 20 years and Im still here. I dont drink the water with minerals added. I drink alot of water and it cant taste like anything at all or I wont drink it.

[Myka]

Originally posted by BuckeyeFS Some systems use a capillary flow restrictor. These restrictors look similar to the plug type, except they have a long, thin (several inches to a foot or so) capillary tube extending from the cap. Again - this type of flow restrictor can be found INSIDE the waste tubing.

This is what I have. I found it. Thanks!

Your pressure, even with clean filters, is low. So I wouldn't think you'd want it to go any lower than 40 psi.

I mis-read it. It actually runs at 50 psi.

That would be an unusual approach. More standard approach would be to replace the block BEFORE you get chlorine break through - carbon blocks come with a specified chlorine capacity - change the clock when you get to about 75% of the chlorine capacity or a 6 months, whichever comes first.

So I should keep track of how many gallons I am producing?

Potentially - remember that the tds in the waste water will be about 20% higher than in your tap water. If you have low tds to start with, it may be fine to drink. If you have high tds to start with, you may not like the flavor. You can use it for laundry, watering the plants, etc... You'll have to specifically look at the quality of the waste water to know if it is ok for your fresh water tanks.

Ahhhhhh, I didn't think of that. I don't really understand how an RO membrane works, so I had no idea that the waste water would have higher TDS than my tap water, but it makes sense. I'll test my tap TDS as soon as my meter gets here (it's in the mail!).

Thanks SO much Russ!!! You helped a lot!

PS I wish I would have bought one of your systems instead. Good prices.

[Myka]

Originally posted by AZDesertRat You WILL want to replace the prefilter and carbon block every 6 months regardless if pressure dropped or not. This is done for several reasons, one is the pressure drop across dirty filters, two is carbon will only adsorb the chlorine from so many gallons of water until it is exhausted and possibly ruins the RO membrane, and three is to reduce or eliminate the possibility or bacteria or virus growth inside the housings. Always disinfect the housings when replacing filters, you should have received directions on how to do this with your unit. If not they are posted here and a quick search will bring them up.

I odn't really understand the 6 month thing. Everyone says "6 months", but what if I am only making 5 gallons per week? I guess the thought of bacterial or viral infections growing the chambers would be a good reason. Good point on disinfecting. I'll go search that out, nothing in my unit instructions. Thanks!

If you are using a good Matrix or Chlorine Guzzler type carbon block you do not have to worry about chlorine getting to the membrane. Matrix blocks in the 0.5-0.6 micron range are good for 20,000 gallons of water at 1 ppm chlorine residual. DO NOT use cheap carbon replacements, some are only good for as little as 300 gallons.

What is cheap then? I was going to use the carbon blocks that J&L Aquatics sells, they are CAD$14. The advertising says "Replacement 5 Micron extruded carbon, CTO Matrikx cartridge for use in RO TFC, Maxxima, Deion and all Aqua FX units. Rated to remove up to 2 ppm chlorine for 3,750 gallons!" At my rate it will take me 14 years to make 3,750 gallons!!! HAHAHA!

http://www.jlaquatics.com/phpstore/s...t_ID=ro-kpcfce

Flush kits are not a proven product. I have never owned one and always get 3+ years or more out of every RO membrane. The only way they can be of any value is if you flush for a few minutes EVERY TIME you are done making water. If you use it hit and miss then it is of no value at all since dissolved solids have begun to harden on the surface of the membrane already and cannot be removed no matter how much flushing you do. No one has ever shown proof that they do anything at all, I wouldn't sweat it. They are more a sales gimmick than anything.

Well, I have one on its way in the mail right now. It was on sale for $13 or something like that. I'll use it every time after I make water. Might as well I suppose!

They waste is fine for lots of uses depending on how bad you water is to begin with. A TDS meter will tell you this. You should have a good handheld TDS meter if you have an RO/DI unit, otherwise you have absolutely no idea if it is working or not or when to replace the DI resin or membrane.

TDS meter in the mail along with the Flush Kit.

Don't get hung up on waste, it all gets recycled anyway, we are not making any new water, it is the same water that has been on Earth for millions of years, no more no less. It will go either back into the ground, recharging the aquifer, on a golf course or any number of uses.

That's an interesting view.

Thanks for your help!!!

[Myka]

Ok, got my TDS meter...here's the readings:

Tap water - 92 ppm - Is this low or high tds for tap water?
After carbon - 86 ppm
After RO - 1 ppm
After DI - 0 ppm



I am using my flush kit for about 2-3 minutes after every use of my unit. Is that often enough "to do the trick"?

[BuckeyeFS]

Your feedwater tds of 92 is very low - that's a good thing.

Don't be concerned with taking a tds reading after your prefilters - they don't affect dissolved solids to any appreciable extent.

Your RO water TDS indicates a 99% rejection rate. Wow! That is very good.

Your DI ought to last a long time given that you are feeding it 1 ppm water.

Flushing as you are should help prolong the life of the membrane.

Russ

[Rwinfrey]

nice unit same one I have I don't think you will need to get a bigger membrane if you are only making 5 gallons per week.If you are worried about pressure you can always get a booster pump dial it in to 60 psi and you are all set BFS can probably help you out with that and so can AQUA FX.Might I recommend some kind of storage with an auto shut off.

[BuckeyeFS]

Originally posted by Rwinfrey
If you are worried about pressure you can always get a booster pump dial it in to 60 psi and you are all set BFS can probably help you

If folks add a booster pump, the Aquatec 880 for example, the pressure is adjustable. We recommend taking full advantage of the pump by adjusting the pressure up to about 90 PSI. Our RO or RODI systems typically have some components (not the membrane!) with a maximum operating pressure of 100 psi.

Russ

[Myka]

Thanks Russ! That is all great news!

I'm not going to upgrade anything on the unit right now. I am working on building myself a 65g setup, so upgrade money is going into that.

The unit is apparently working quite well at 50-52 psi, so I'll take that for now.

I'm not sure a float switch and a storage tub would make my life any easier. I find the 5 gallon jugs really easy to use. Easy to lift, easy to pour. I don't have an ATO on my tank right now, so I do topoffs by hand, and the 5 gallon jugs are good for that. Space is a HUGE concern as I live in a small condo unit that has next to nil for storage space. I just put my 5 gallon jug in the sink, and I know it takes 3 hours to fill. If it runs over it just goes down the drain.