Can i use an old RO?

[plecocicho]

Hello,
i have an old ro (was used for 2 years), that hasnt been used for little more than two years. I started it again today and the productivity and ratio were normal. The only difference is, that the permaet has a conductivity of 40 microsiemens (tap has 380 microsiemens) and GH and KH of 1,5. You think i could use this ro, or is the mebrane to damaged so the carbonates will creep over the use and can i use such permaet from the old ro? I plan to couple two membranes, so the waste water from the first would go into the incoming water for the second membrane, thus achieving higher production and decreasing waste :permaet ratio.

[DiscusLoverJeff]

I would change the membrane and filters and you will be good to go. The membrane if it sat dry for years is more than likely no good.

[nc0gnet0]

I plan to couple two membranes, so the waste water from the first would go into the incoming water for the second membrane, thus achieving higher production and decreasing waste permeat ratio.


You can do this, but you might be a bit disappointed in he results. One thing to consider, is the back pressure to the first membrane will be increased when you do this, and as a result will shorten it's life span. Better off getting a booster pump IME, or getting two additional membranes and a booster pump, feeding the waste water outs from two membranes into a third.

-Rick

[plecocicho]

So if i couple the two mebranes, the first one will suffer more, but not the second one? Can you elaborate more where should i put booster pump if i use one and where when i use two membranes?

[nc0gnet0]

So if i couple the two mebranes, the first one will suffer more, but not the second one? Can you elaborate more where should i put booster pump if i use one and where when i use two membranes?


Yes the first membrane will experience an increase in back pressure, this will "force" more water through the membrane causing is to "scale" faster. Commercial membranes do exactly this to get better product water to waste water ratio's, but they typically have automated flush timers to help with membrane life. The second membrane will also have significantly less pressure than the first, reducing it's output. I am not saying what you propose will not work, but there will be trade-offs and you will not get 2x the output water expected.

Booster pump should go inline prior to the pre-filters.

[plecocicho]

So it the first ro has a manual flushing valve, it can prolong membrane life?

[nc0gnet0]

In theory, yes. Bear in mind on the commercial units with increased backpressure they are flushed roughly every hour for 30 seconds.

[Buckeye Hydro]

Hello,
i have an old ro (was used for 2 years), that hasnt been used for little more than two years. I started it again today and the productivity and ratio were normal. The only difference is, that the permaet has a conductivity of 40 microsiemens (tap has 380 microsiemens) and GH and KH of 1,5. You think i could use this ro, or is the mebrane to damaged so the carbonates will creep over the use and can i use such permaet from the old ro?

All the existing filters should be tossed. The unit should be sanitized, and then new filters, including the membrane, loaded.

Russ

[plecocicho]

Well i finally got an ro with a flushing valve and the results scare me a little. On its own, ro with a valve (190l/day) gives me 10l of osmose water and 20 l of waste water (nominal 240l/day, 50 l more than it says). Coupled together with the second membrane i get 14 l of permaet and only 12 l of waste water! Permaet of the first osmosis has a conductivity of 20 microS, permaet of the second one 20 microS, waste of the first one 510 and combined waste (when coupled ) of 710 microS; tap water has a conductivity of 380 microS. So, when coupled i have a ratio, where i get more permaet than waste water. I used the coupled system twice (once 2h+, second one 1h+), both times i flushed the first osmosis for a couple of minutes.

[nc0gnet0]

bear in mind you have effetively increased the back pressure to the first ro membrane which in turn will force more water through that membrane. yes, you will have a net increase in product water, albeit at the expense of shorter membrane life. Be sure to flush the membrane often to help offset this.

To test this out, uncouple the second membrane althogether, and time how long it takes for the first membrane to output 2l of water (fill a soda bottle).

Then repeat the test, attaching the second membrane, but only timing the output of the first (with the second attached).

-Rick

( I am assuming that when you say you coupled the second membrane you are feeding it with the waste water out of the first).

[Buckeye Hydro]

Well i finally got an ro with a flushing valve and the results scare me a little. On its own, ro with a valve (190l/day) gives me 10l of osmose water and 20 l of waste water (nominal 240l/day, 50 l more than it says). Coupled together with the second membrane i get 14 l of permaet and only 12 l of waste water! Permaet of the first osmosis has a conductivity of 20 microS, permaet of the second one 20 microS, waste of the first one 510 and combined waste (when coupled ) of 710 microS; tap water has a conductivity of 380 microS. So, when coupled i have a ratio, where i get more permaet than waste water. I used the coupled system twice (once 2h+, second one 1h+), both times i flushed the first osmosis for a couple of minutes.

Yeow. Sorry but I'm having a hard time following your thoughts here. Again, if you'd like to give us a call when you are in front of your system we'd be happy to resolve all your questions.

Russ
513-312-2343

[plecocicho]

For a better understandment of what i am talking about.
Here is picture of the osmosis coupling, that i have, only with two differencies: i only coupled one extra osmosis, not three and secondly, my first osmosis has a flushing valve. The idea behind it is, that you invert the the waste water into the the second osmosis. By this way you get a higher yield (in my case even higher than waste water), but you shorten your membranes life. Thats why i use the flushing valve on the first osmosis.

Rick, if i use only one membrane i get to 2l in 12 minutes. I did test the outlet of both permaets and a waste water when both osmosis were connected. i counted how long would it take to fill 20 ml cup. First permaete and a waste water needed 14 counts (app. seconds), the second permaete took around 34-36 counts. Yes i flush after each use. How long shoud i flush it after each use and would a little opening of the flush vlave prolong membrane life (i didnt see any change in a flow of all effluents (permaete and waste ) when i fully opened the flush valve. ).
I hope i made my case clearer.

And Russ i am from Europe, Slovenia to be precise, so its a little expansive to call you. Appreciate the helping hand though.



http://www.aquanubis.com/forum/resources/zaporedna-vezava-4-ro-enot/27850

[Buckeye Hydro]

You'll want to check the specks on the little taste and odor (GAC) inline filter and make sure you don't exceed the max flow rate. I'd change it out at about half the stated chlorine capacity.

[nc0gnet0]

I see 4 ro membrane housings? but only 1 sediment and 1 carbon block, is that correct?

If that is the case you need to upgrade your sediment/carbon block filtration, as Russ has stated.

[plecocicho]

No, i have only one extra membrane, not three like in the picture. Yes i only have one sediment and carbon filter, the water flows like this: tap valve-sediment filter-carbon filter-first osmosis-waste into the second osmosis. As a pressure, you mean if the filters cant take the full water pressure? Why would i need filters on rhe second osmosis, isnt waste water devoid of chlorine, small particles? Thanks

[nc0gnet0]

Rick, if i use only one membrane i get to 2l in 12 minutes. I did test the outlet of both permaets and a waste water when both osmosis were connected. i counted how long would it take to fill 20 ml cup. First permaete and a waste water needed 14 counts (app. seconds), the second permaete took around 34-36 counts.

I understand this, and yes, you have increased product water and decreased waste water.

I want you to perform a different test. The purpose of this test it so show you what is happening to the first membrane. To do this test, time the amount of time it takes to fill the cup with ONLY the product water from the FIRST membrane. The water coming out of the second membrane is of no concern for this test. perform this test first with the second membrane disconnected (and the waste water line vented to a drain). Then, reconnect the second membrane and do the test again. YOu should notice that the when the second membrane is connected, the first membrane outputs more product water.


How long shoud i flush it after each use and would a little opening of the flush vlave prolong membrane life (i didnt see any change in a flow of all effluents (permaete and waste ) when i fully opened the flush valve. ).



Personally I would automate the flushing with solenoid valves and a timer, and install on both membranes.The fact you see no difference with the flush valve open leads me to believe you have not installed it properly, can you take a picture a bit further away from your setup so I can see all the connections and the fush valve?


-Rick

[plecocicho]

http://i738.photobucket.com/albums/xx22/plecocicho/Fotografija0135.jpeg (http://s738.photobucket.com/user/plecocicho/media/Fotografija0135.jpeg.html)
http://i738.photobucket.com/albums/xx22/plecocicho/Fotografija0137.jpeg (http://s738.photobucket.com/user/plecocicho/media/Fotografija0137.jpeg.html)

From L-R:sedimen filter-osmose 1-carbon filter-osmose 2.
Short video:

https://www.youtube.com/watch?v=kIkS2yV2Igc

When only one membrane is connected RO 1 produces 2l in 12 minutes, when both membranes are connected RO 1 produces 2l in 12 minutes and 37 seconds. When connected RO 2 membrane produces 2l in 29 minutes. Both filters can endure max pressure of 125 psi.

[discusnutts]

if you are getting those low values with your RO then odds are the membrane is fine.

if the membrane were damaged the values would be close to source water.

it wouldn't hurt to replace the gac and the manual filters but the RO membrane is likely fine

D

[Len]

If the unit sat around for that long, I'd be less concerned with it's effectiveness and more concerned with mold/mildew that probably developed from the dampness sitting trapped in the housings and membranes.

[plecocicho]

Guys, i bought a new ro with a flushing valve. The " issue" is that i achieved a yield larger than 1:1 (10l ro1, 4 l ro2 and 10 l of waste water), when i combined both osmosis, so that waste water from the first flows into the second membrane and that when combined, open flush valve increases the flow of the second permaet instead of the waste water.

[Buckeye Hydro]

Sounds like you have it plumbed wrong, and you're using the wrong flow restrictor.

[Buckeye Hydro]

I have a hard time understanding your posts - are you saying you have two membranes plumbed in series (waste from the first feeding the second, and the only chlorine removal is a single inline taste and odor filter? If so, you'll need new membranes soon.

Russ

[plecocicho]

Yes, thats what i am saying. Why would a single sediment and carbon filter be an issue? Because of the back pressure?

[Buckeye Hydro]

Understand that a taste and odor filter is simply a small "tube" with some standard GAC in it. GAC will remove chlorine, but not very well, and not very much, when compared to a good quality carbon block. Standard GAC really has no place as a prefilter for a high capacity RO system. GAC prefilters are sometimes still used - teamed with a carbon block - on very low capacity drinking water RO systems. Think something like a 12 gallon per day RO membrane. These are full size (10" x 2.5" GAC cartridges. What you have is smaller, and is intended to be used between a pressure tank and a faucet to remove taste and odor, not chlorine. Now, you've added a second membrane, which will exacerbate the problem. My advice to you is to get rid of the low capacity inline sediment filter and gac in favor of full size 10" x 2.5" cartridges. If you don't want to do that, just make sure you:
1. Monitor pressure entering the first membrane so that you know when the sediment filter is clogging.
2. Replace the taste and odor filter frequently. If you don't (and even if you do), you'll get chlorine making its way to the membranes - which will ruin them.

Russ

[plecocicho]

Thanks Russ. I consulted with Nandi, who used to sell ROs. He said that i should connect my two osmosis in this way: both prefilters- first membrane-waste water line with removed flow restrictor-second membrane with flow restrictor(420 ml) and flush valve. He also mentioned the carbon block as the weak point. I usually use 60 liters of osmosis per week, so by my calculations i still have another 2000 liters to go (if the usage remains the same). Those 3000 liters are meant to be permaet (clean water) or the amount of tap water passing through the membrane?

[Buckeye Hydro]

There is nothing wrong with plumbing two membranes in series, as long as you use a flow restrictor that yields about a 4 to 1 ratio of concentrate to permeate.

The chlorine capacity you're reading on the inline taste and odor filter applies to the total amount of water that goes through it, so it INCLUDES the concentrate (waste). Don't use the cartridge beyond about 2/3rds of its stated capacity, if that. Also - don't exceed the flow specification on the filter - typically 0.5 gallons per minute. Assuming you have two 75 gpd membranes, and run at a 4 to 1 ratio, you have
150 gpd permeate
600 gpd concentrate
750 gpd total = 0.52 gpm, which exceeds the flow limit.

I recommend you change the configuration of your system. Those inline filters are not a good fit the way you are using them, and they are expensive in that you have to replace them often, and they are encapsulated.

Russ

[Buckeye Hydro]

A 420 ml/min flow restrictor is appropriate for a 50 gpd membrane at factory spec pressure and temperature. What is the GPD rating on each of your membranes?

[plecocicho]

190 l/day. I dont know how much in gallons is that. Also my tap water has usually a gh of 8-10, rarely 12 dgh and a conductivity of 370-420 microsiemens.
I get 1:2 ratio just with one osmosis plumbed to the tap.

[Buckeye Hydro]

190L/D = 50 GPD.

So you are running two 50 gpd membranes thru a flow restrictor intended for a 50 gpd membrane. Ugh.

[plecocicho]

Well, both membranes have a flow restrictor, the one with the flushing valve 420ml and one without it 300 ml.

[Buckeye Hydro]

When you plumb membranes in series, you should be using 1(one) flow restrictor, not two. Membranes plumbed in series behave like a single, long membrane.

[nc0gnet0]

When you plumb membranes in series, you should be using 1(one) flow restrictor, not two. Membranes plumbed in series behave like a single, long membrane.

Or, if you use two flow restrictors, use them for 1/2 the normal value. I prefer this method with separate flush valves at each restrictor. This allows you to focus on one membrane when flushing (gives a tad bit more pressure to the membrane being flushed).


-Rick

[Buckeye Hydro]

Or, if you use two flow restrictors, use them for 1/2 the normal value. I prefer this method with separate flush valves at each restrictor. This allows you to focus on one membrane when flushing (gives a tad bit more pressure to the membrane being flushed).


-Rick

Two flow restrictors is a fine approach, if the membranes are plumbed in PARALLEL, not in series. We do this frequently.

[plecocicho]

So how big flow restrictor should i use?

[Buckeye Hydro]

Here's some guidance:

First - remember that what folks call "waste water" really would be better thought of as "flush water" in that this water serves the important purpose of internally flushing the surface of the semipermeable membrane to keep the membrane from fouling/scaling.

When you configure a system with two membranes in series (the waste from the first membrane going to the "in" port on the second membrane), for this discussion let's say it's two 75 gpd membranes, the system behaves like you have a single long (75 gpd x 2) 150 gpd membrane.

Now - if you use a proper flow restrictor, that is, one for a 150 gpd membrane, and have something near the factory spec water pressure and temperature, you'll have about a 4:1 waste to product ratio. Sounds familiar, right?

If however you don't change the flow restrictor - meaning you keep using the same restrictor you were using when you just had one 75 gpd membrane, then you'll see a waste to product ratio much lower than 4:1. But remember that the recommendation for a ~4:1 ratio comes from membrane manufacturers. They are telling you that you need about a 4:1 ratio to keep the membrane flushed and keep the membrane from fouling or building up scale. Run the system with a lower ratio and you will foul/scale the membrane(s) quicker than would have otherwise been the case.

Instead of adding a second membrane to lower that ratio, you could have just changed out your flow restrictor ($4) instead. This is a much less expensive approach to get you to the same endpoint in terms of saving on waste water.

Now, to confuse things just a bit. Filmtec specs call for the 4 to 1 ratio on the basis of assumptions about the water that will be supplied to the membrane. If you have very soft water you MAY be able to get a decent service life from the membrane running at a ratio lower than 4 to 1 (e.g., 3 to 1). Remember that the waste water from the first membrane is about 25% harder than your tap water.

Bottom line: If what you are after is reduced waste water, experiment with a different flow restrictor for $4 instead of messing around with a second membrane plumbed in series.

As a side note, you can also lower the ratio by increasing the pressure delivered to the membrane (with a booster pump), because flow restrictors are sized assuming you are providing factory spec conditions (50 psi and 77 degrees for Filmtec membranes). Increase the pressure and you'll drive more water through the membrane and viola - less waste water. But as mentioned above, if you do this (just like over-restricting a membrane) - the lower the waste to product ratio, the shorter the lifespan on the membrane.

Makes sense?

With 2x50=100 gpd membrane, you'll want something in the 700 to 800 ml/min range.

Russ

[nc0gnet0]

Two flow restrictors is a fine approach, if the membranes are plumbed in PARALLEL, not in series. We do this frequently.


Actually I run a combination of the above, with multiple booster pumps as well. :) I know some of my membranes have more that the normal amount of backpressure, but I try to compensate by using automatic solenoid valves on a timer that flush the membranes every 4 hours for roughly 30 seconds, I have found doing so greatly extends my membrane life.

Running two membranes in parallel works fine to increase output, however does nothing to the product water to waste water ratio.

And as you have told me Russ, these "piggyback" configurations you see advertised (the add-on's) again run the risk of drawing more gph that the carbon block can handle.

Off course, the actuall amount of water a carbon block filter can handle is greatly influenced by the levels of chlorine in the water. While I am cursed with liquid rock for water, I get one small break with the fact my water has relatively low chlorine (.5ppm).

[nc0gnet0]

Here's some guidance:

First - remember that what folks call "waste water" really would be better thought of as "flush water" in that this water serves the important purpose of internally flushing the surface of the semipermeable membrane to keep the membrane from fouling/scaling.

When you configure a system with two membranes in series (the waste from the first membrane going to the "in" port on the second membrane), for this discussion let's say it's two 75 gpd membranes, the system behaves like you have a single long (75 gpd x 2) 150 gpd membrane.

Now - if you use a proper flow restrictor, that is, one for a 150 gpd membrane, and have something near the factory spec water pressure and temperature, you'll have about a 4:1 waste to product ratio. Sounds familiar, right?

If however you don't change the flow restrictor - meaning you keep using the same restrictor you were using when you just had one 75 gpd membrane, then you'll see a waste to product ratio much lower than 4:1. But remember that the recommendation for a ~4:1 ratio comes from membrane manufacturers. They are telling you that you need about a 4:1 ratio to keep the membrane flushed and keep the membrane from fouling or building up scale. Run the system with a lower ratio and you will foul/scale the membrane(s) quicker than would have otherwise been the case.

Instead of adding a second membrane to lower that ratio, you could have just changed out your flow restrictor ($4) instead. This is a much less expensive approach to get you to the same endpoint in terms of saving on waste water.

Now, to confuse things just a bit. Filmtec specs call for the 4 to 1 ratio on the basis of assumptions about the water that will be supplied to the membrane. If you have very soft water you MAY be able to get a decent service life from the membrane running at a ratio lower than 4 to 1 (e.g., 3 to 1). Remember that the waste water from the first membrane is about 25% harder than your tap water.

Bottom line: If what you are after is reduced waste water, experiment with a different flow restrictor for $4 instead of messing around with a second membrane plumbed in series.

As a side note, you can also lower the ratio by increasing the pressure delivered to the membrane (with a booster pump), because flow restrictors are sized assuming you are providing factory spec conditions (50 psi and 77 degrees for Filmtec membranes). Increase the pressure and you'll drive more water through the membrane and viola - less waste water. But as mentioned above, if you do this (just like over-restricting a membrane) - the lower the waste to product ratio, the shorter the lifespan on the membrane.

Makes sense?

With 2x50=100 gpd membrane, you'll want something in the 700 to 800 ml/min range.

Russ

This is a great explanation, one thing, shouldn't running two membranes in series give you roughly 2x the life of the single membrane (more surface area to foul)? But when you have to replace them it will cost you 2x as much, so, pretty much an even trade off.

[Buckeye Hydro]

Max flow on good 10" x 2.5" carbon blocks is 1.0 gpm.

[plecocicho]

So i should get a flow restrictor meant for 100 gpd or higher? Doesnt flushing decreases scaling? Well i gues warmer temperatures, softer water and high pressure helps me to get a higher yield from getgo (192 for 300ml restrictor, 240 for 420 ml restrictor).Do you know anyone who sells cheap flow restictor besides looking up on ebay.

[Buckeye Hydro]

So i should get a flow restrictor meant for 100 gpd or higher? Not higher. 100 gpd.



Doesnt flushing decreases scaling?
Yes - that's the idea.


Well i gues warmer temperatures, softer water and high pressure helps me to get a higher yield from getgo (192 for 300ml restrictor, 240 for 420 ml restrictor).

Sorry - I don't understand.


Do you know anyone who sells cheap flow restrictor besides looking up on ebay.
We do.

[plecocicho]

I meant to say that those factors (t, pressure, water hardness) help me to achieve high yield with both osmosis, just that one has 300 and the other 420. restrictor. i have used the same membrane in another part of slovenia with harder water and only got 6l per hour instead of 8-10 l per hour that i get now.

[plecocicho]

Do you ship to Slovenia in Europe too?

[Buckeye Hydro]

No sir. Sorry.

Try http://www.ro-man.com/shop/index.php?route=product/category&path=26_46 in the UK.

Russ