Help with water purification decsion
- Thread starter jnarowe
- Start date
Well unless you have a need for a special filter cause you have high ammonia, silicate, phosphates or something like that in the tap water there isn't much point in paying for special cartridges when you don't need them like in my case.
What you will get is 50% more production with half the waist water. You could go with even higher flow membranes but then your loosing on your rejection and hurting your DI stages since most of them go from 96/98 to 88/90 rejection rates.
Personally, I'd try it like this and if you see you still have good pressure and need even more water then you may be able to add another membrane getting you to around 250 gpd with even less waist water.
Carlo
What you will get is 50% more production with half the waist water. You could go with even higher flow membranes but then your loosing on your rejection and hurting your DI stages since most of them go from 96/98 to 88/90 rejection rates.
Personally, I'd try it like this and if you see you still have good pressure and need even more water then you may be able to add another membrane getting you to around 250 gpd with even less waist water.
Carlo
jnarowe
New member
I am thinking about those exact same membranes. Still haven't pulled the trigger yet as I am waiting to hear back about the warranty on my booster pump. I have some brain dysfunction so it's hard for me to get my act together. I am keeping up with my top-off, but I really want to revamp my entire RO/DI system. Float switches, solenoids, etc.
Just to clarify something I said earlier about running two membranes in series. It's not really a savings of 50% on the waist water.
For example if your are running 4:1 then for every 5 gallons going through your RO membrane 1 gallon comes out (20%). If you now feed that 4 gallons of waist water into the 2nd membrane you'll get out 0.8 gallons with 3.2 gallons going to waist.
So adding the 2nd membrane assuming 4:1 will get you a total of 1.8 gallons of good water with 3.2 gallons of waist.
You went from 20% effective to 36% effective based on the same amount of water running through it. If you were able to add a 3rd membrane you would go up to 48.8% (3.2 waist fed to 3rd membrane would get 0.64 good).
When you start adding multiple membranes you can lower your waist ratio some. Instead of 4:1 you could go to 3:1. With 1 membrane it would be 25%, 2 membranes at 43.75% and with 3 membranes at 57.81%
1 gallon good out of 4 total gallons
3 gallons waist into 2nd membrane gets you 0.75 gallons (1.75 total) good and 2.25 gallons waist
2.25 gallons fed to 3rd membrane gets you 0.5625 (2.3125 total) gallons good and 1.6875 waist
Carlo
For example if your are running 4:1 then for every 5 gallons going through your RO membrane 1 gallon comes out (20%). If you now feed that 4 gallons of waist water into the 2nd membrane you'll get out 0.8 gallons with 3.2 gallons going to waist.
So adding the 2nd membrane assuming 4:1 will get you a total of 1.8 gallons of good water with 3.2 gallons of waist.
You went from 20% effective to 36% effective based on the same amount of water running through it. If you were able to add a 3rd membrane you would go up to 48.8% (3.2 waist fed to 3rd membrane would get 0.64 good).
When you start adding multiple membranes you can lower your waist ratio some. Instead of 4:1 you could go to 3:1. With 1 membrane it would be 25%, 2 membranes at 43.75% and with 3 membranes at 57.81%
1 gallon good out of 4 total gallons
3 gallons waist into 2nd membrane gets you 0.75 gallons (1.75 total) good and 2.25 gallons waist
2.25 gallons fed to 3rd membrane gets you 0.5625 (2.3125 total) gallons good and 1.6875 waist
Carlo
jdieck
New member
Carlo:
Carlo:
Actually it does not really work like that The restrictor you need to use for the combined membranes is the same as if you were using a single membrane. The flow trough the restrictor will be the same as with one membrane, in other words the same waste volume but because you are doubling the membrane area (two in series is equivalente to one membrane twice as long) now you get twice the product volume.
So if with one membrane you have a restrictor that give you 4:1 the same restrictor will give you 4:2
In actual practice it is not exactly half because the second membrane is seeing a bit more impurities and slightly lower inlet pressure but it really get close to that.
Note that this is true only if you are able to maintain good inlet pressure and this is were the booster pump comes into play as you will have some pressure drop between membrane 1 and membrane 2 of about 2 to 5 psi that you need to overcome.
918ReefCpl
Member
I'll 2nd AZDesertRats opinion - he's well regarded for his knowledge of water treatment by his fellow RC'rs in Az. Also, SpectraPure is releasing their newest creation in Sept. Its a MaxCap RO/DI unit that instead of the 4:1 ratio (waste/pure) it is now going to be 1:1 ratio...just some more food for thought...
jnarowe
New member
1:1? How the hell are they going to do that? I have been looking at all sorts of systems like Merlins etc. and the Merlin is strangely attractive to me if followed by some resin canisters. With my low TDS, my biggest issue is phosphate and nitrate, but I can't get a clear answer on what the rejection rate of the Merlin is. I also can't figure out what the filters/membranes would cost to replace and it is suggested at 6 month intervals.
A couple of Typhoon membranes would give me a lot more water and still enable me to produce enough water should one need to be taken offline. That's my current problem now is that I cannot make enough without the pump, which is esentially like cutting performance in half.
Then there's this semi commercial setup:
I don't like canisters I cannot see through though.
A couple of Typhoon membranes would give me a lot more water and still enable me to produce enough water should one need to be taken offline. That's my current problem now is that I cannot make enough without the pump, which is esentially like cutting performance in half.
Then there's this semi commercial setup:
I don't like canisters I cannot see through though.
AZDesertRat
In Memoriam
The Merlin is not very efficient, its more like a 100 GPD nano filter at 90% rejection.
The new Spectrapure unit is supposed to be microprocessor controlled and uses DI water to flush the membrane at specific intervals for a better flush and less continous waste.
Actually I prefer canisters I cannot see through. If your system is working as it should there should be nothing to see anyway. Opaque housings are also stronger than clear as they are not as brittle and they do not promote bacteria and virus growth since sunlight cannot get to the filters. Better all around.
The new Spectrapure unit is supposed to be microprocessor controlled and uses DI water to flush the membrane at specific intervals for a better flush and less continous waste.
Actually I prefer canisters I cannot see through. If your system is working as it should there should be nothing to see anyway. Opaque housings are also stronger than clear as they are not as brittle and they do not promote bacteria and virus growth since sunlight cannot get to the filters. Better all around.
jnarowe
New member
good point about the canisters. I'll keep that in mind. Not sure what you mean about the Merlin. It's supposed to be 92% which is still quite low, but continuous feed, like for whole house applications.
In fact I just got a message back from a reseller of it saying that I could install it in the whole house configuration and just use DI in my tank room. Not sure if that is accurate, since I think the water will pick up TDS from the pipes, and at 92% rejection, I would definitely be using a lot of resin. BUT, never have to worry about volume.
I know there are reefers that use resin only systems too, serviced by companies that do it for medical needs. Really, I am without the pump, looking to install a bigger tank (but can't get to it right now) and looking for the best way to either use what I have or just pop in a new system. I have been very suspicious of the 150gpd membranes but they are supposedly 98% rejection, which in my case would give me about 1.4 TDS output. That's below the 3.0 I am currently getting.
Would you recommend getting the pump and just waiting for the new SpectraPure unit, installing 150gpd membranes (I just installed new 75 gpd ones about a month ago), or what? Sorry to draw this out. I have difficulties decision making since my brain injury and I really HATE finding out that I made the wrong decision or got screwed in some way.
I sincerely appreciate all who are contributing to this thread, as I am unhappy with my RO/DI volume and feel that with the appropraiate steps, it could be very robust.
In fact I just got a message back from a reseller of it saying that I could install it in the whole house configuration and just use DI in my tank room. Not sure if that is accurate, since I think the water will pick up TDS from the pipes, and at 92% rejection, I would definitely be using a lot of resin. BUT, never have to worry about volume.
I know there are reefers that use resin only systems too, serviced by companies that do it for medical needs. Really, I am without the pump, looking to install a bigger tank (but can't get to it right now) and looking for the best way to either use what I have or just pop in a new system. I have been very suspicious of the 150gpd membranes but they are supposedly 98% rejection, which in my case would give me about 1.4 TDS output. That's below the 3.0 I am currently getting.
Would you recommend getting the pump and just waiting for the new SpectraPure unit, installing 150gpd membranes (I just installed new 75 gpd ones about a month ago), or what? Sorry to draw this out. I have difficulties decision making since my brain injury and I really HATE finding out that I made the wrong decision or got screwed in some way.
I sincerely appreciate all who are contributing to this thread, as I am unhappy with my RO/DI volume and feel that with the appropraiate steps, it could be very robust.
AZDesertRat
In Memoriam
75 GPD membranes with a pump should give you excellent results. I have a dual membrane system without a pump but have 68 psi at the RO and get 240 GPD with a 99.23% average rejection rate. Adding a pump would really get me lots of water but 240 GPD is more than I need as it is.
There are better, more efficient ways to get water than the Merlin.
There are better, more efficient ways to get water than the Merlin.
jnarowe
New member
Yeah I am on a well that is quite a ways away and below the level of my house, so I am only getting about 40psi. You are getting 240gpd from two 75gpd membranes, or did I misunderstand? True the flow was pretty good when the pump was running, but I am really looking into a higher capacity situation. But if I can fill the 200g tank in a day, I think that would be OK. I only change out about 85g at a time once per week from the main system, but I am topping off two systems also.
What membranes/system are you using to get 99.23% rejection, and how do you get such a precise number?
So fill me in! Clearly better rejection rates are good, but can you explain "better".
What membranes/system are you using to get 99.23% rejection, and how do you get such a precise number?
So fill me in! Clearly better rejection rates are good, but can you explain "better".
I've never ran 2 membranes before so I was only going by what a particular vendor mentioned here in this thread explained to me. He very carefully said most people don't understand this and "think" it's 1/2 but that it isn't. He said the membranes are designed and should be run at 4:1 ratio regardless of if you have one or 10 in the system. The 2nd membrane would still need a 4:1 ratio ect... However with multiple membranes you can sometimes cut the ratio back to 3:1 with good results.
I'm not sure I follow what the length has to do with it. A 20" Filmtec membrane still runs at 4:1 just as a 10" membrane does.
Basically I was told you run the membranes exactly the same but feed the waist of the first directly into the second. Each would still have the flow restrictor in place to keep the pressure correct and keep the membrane clean.
So you are saying you remove the flow restrictor on one of the membranes (1st I'd assume)? Could you explain it a little better?
Carlo
PS I realize the 2nd membrane is going to have more TDS coming out of it because it was waist from the 1st. Don't worry about trying to explain the TDS issue.
AZDesertRat
In Memoriam
I have two Spectrapure hand tested Select series membranes, a 90 GPD and a 150 GPD. They may cost a little more initially due to the hand testing and guarantee but they quickly pay for themselves in greatly increased resin life due to the higher rejection rates. I use a HM Digital COM-100 handheld TDS meter calibrated for low range accuracy. Its the only reliable meter that will read down to the tenths and actually register less than an indicated 0 TDS, down into the megaohm or microsiemen ranges.
Piggyback membranes with a booster pump will equal a Merlin in GPD and with much higher rejection meaning longer DI life. There are good 150 GPD membranes on the market, if you can find 2 of them and combine them they will produce much more than 300 GPD at a 98% rejection rate instead or 90 or 92.
Piggyback membranes with a booster pump will equal a Merlin in GPD and with much higher rejection meaning longer DI life. There are good 150 GPD membranes on the market, if you can find 2 of them and combine them they will produce much more than 300 GPD at a 98% rejection rate instead or 90 or 92.
jnarowe
New member
Great post. I really appreciate your time and you are basically confirming what Weast and Sherman have been telling me to do. I have been using two different SpectraPure resins (1:2) that they put in their MaxCap setup and it does seem to last longer.
So, let me make sure I understand you completely on the membranes. You are saying that I can install two 150gpd high quality membranes into my current system, maybe clean up the resin canisters as the Water General one is a little funky, put the pump back on and I will be good to go? No reason to replace the entire setup?
And may I PM you about a membrane supplier?
So, let me make sure I understand you completely on the membranes. You are saying that I can install two 150gpd high quality membranes into my current system, maybe clean up the resin canisters as the Water General one is a little funky, put the pump back on and I will be good to go? No reason to replace the entire setup?
And may I PM you about a membrane supplier?
jdieck
New member
Yes in the series configuration you use only one restrictor in the waste of the second membrane and sized for the capacity of a single membrane (150 gpd membrane restrictor in your case), you do not use a restrictor on the first. Here is the configuration up to the membranes output. Install the booster pump after the carbon before the first membrane.
From here the blue line goes to the first DI cartridge in the series.
What your vendor does not yet figure out is that with this configuration the first membrane gets a 5:1 and the second a 4:1 ratio. By the way, did you already purchased the 150 gpd membranes? for your quality of water I would have elected two 75 gpd ultrahigh rejection membranes (99+% rather than 98%) to reduce DI costs.
http://spectrapure.com/huds/DUAL.pdf
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I exhausted my ability to contribute a long time ago, but I feel the need to thank you, Jonathon, for dragging this out and getting really good answers and many viable possibilities. I have learned a lot about this particular topic that I sincerely feel I would not have otherwise considered.<a href=showthread.php?s=&postid=10516712#post10516712 target=_blank>Originally posted</a> by jnarowe
I sincerely appreciate all who are contributing to this thread, as I am unhappy with my RO/DI volume and feel that with the appropraiate steps, it could be very robust.
I, too, thank all those contributing to the general knowlege-base that this thread is rapidly becoming!
:thumbsup:
I can see why you don't need two flow resistors but I still don't get the 50% waist reduction. I can't see how the 1st membrane is going to work any different then in a one membrane system. It would appear the 2nd membrane is going to get slightly tainted (higher TDS) water as it's input.
Would you agree that if we pump 5 gallons through the unit the first membrane is going to put out 1 gallon of good water with 4 gallons going to waist (4:1)?
The 2nd doesn't know anything about the other membrane and works like any other membrane at 4:1. If it sees 4 gallons of water at it's input then you'll get 0.8 gallons of good water with 3.2 gallons going to waist.
So I'd think you get a total of 1.8 gallons with 3.2 gallons going to waist from the 5 total gallons going through both membranes.
If this isn't how it's going to work can you tell me how many gallons of good/waist will come out of the first membrane and how much of each will come out of the second membrane?
I already have a couple 75s and 2 150s sitting on the shelf from a month ago. I was going through them so fast I got a few on a "bulk" order.
Since I've got the 150s I'm going to go that route and see what the rejection rate is like. As you know I'll be running the seperate resin beds followed by the mixed bed DI. I can recharge the seperate resins.
Charles from Specacure gave me a call yesterday and we talked for a while about possible other problems which I'm looking into that could be the cause of my membrane failures. Once I get this figured out I'll re-evaluate a good high quality membrane(s) depending on water need and resin use.
Carlo
Would you agree that if we pump 5 gallons through the unit the first membrane is going to put out 1 gallon of good water with 4 gallons going to waist (4:1)?
The 2nd doesn't know anything about the other membrane and works like any other membrane at 4:1. If it sees 4 gallons of water at it's input then you'll get 0.8 gallons of good water with 3.2 gallons going to waist.
So I'd think you get a total of 1.8 gallons with 3.2 gallons going to waist from the 5 total gallons going through both membranes.
If this isn't how it's going to work can you tell me how many gallons of good/waist will come out of the first membrane and how much of each will come out of the second membrane?
I already have a couple 75s and 2 150s sitting on the shelf from a month ago. I was going through them so fast I got a few on a "bulk" order.
Since I've got the 150s I'm going to go that route and see what the rejection rate is like. As you know I'll be running the seperate resin beds followed by the mixed bed DI. I can recharge the seperate resins.
Charles from Specacure gave me a call yesterday and we talked for a while about possible other problems which I'm looking into that could be the cause of my membrane failures. Once I get this figured out I'll re-evaluate a good high quality membrane(s) depending on water need and resin use.
Carlo
jnarowe
New member
Carlo,
Something you wrote above makes me think of a perplexing issue I had a few months ago. I ended up swapping out all membranes, filters etc. only to have the problem continue, and that was TDS in my output. Then a comment by Marc (melev) made me feel about as dumb as a rock.
He asked if I had the resin canisters installed in the correct direction. He also pointed out that there are arrows on the sides to aide in knowing which direction to install them. When I checked, sure enough I had them in wrong, and when I remedied that, all was right with the world.
When they are in wrong, they do not allow proper flow, and testing the effluent of the membrane shows a spike. Mine went from 3.0 TDS to 6 - 9.0 TDS from the membrane and I was going through resin really fast. So, check your install dude!
Something you wrote above makes me think of a perplexing issue I had a few months ago. I ended up swapping out all membranes, filters etc. only to have the problem continue, and that was TDS in my output. Then a comment by Marc (melev) made me feel about as dumb as a rock.
He asked if I had the resin canisters installed in the correct direction. He also pointed out that there are arrows on the sides to aide in knowing which direction to install them. When I checked, sure enough I had them in wrong, and when I remedied that, all was right with the world.
When they are in wrong, they do not allow proper flow, and testing the effluent of the membrane shows a spike. Mine went from 3.0 TDS to 6 - 9.0 TDS from the membrane and I was going through resin really fast. So, check your install dude!
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