Rodi

[jgraz]

It's amazing what a proper system is capable of. I tried to use a small portable system without a pump and basically ended up buying my water for the last 8 months. Bought this from tgee. I can already feel the extra money in pocket. For the very few of those still buying water. This is a must.

 

[Hawkeye]

what does a pump do for the rodi? i am asking (sometimes internet doesn't read that way) and not being rhetorical/sarcastic.

 

[jgraz]

My home pressure was pretty low. 42 psi on a good day. It was taking me about 5-6 hrs to make 5 gal of water. If I was lucky. With the booster pump it increased my pressure to about 85psi. I was making about 5 gals an hr now.

 

[Hawkeye]

Ahhhhhhhhhhhh i never knew that the water pressure could be so low! thanks.

 

[Tazmaniancowboy]

Ahhhhhhhhhhhh i never knew that the water pressure could be so low! thanks.

My well water pressure is 30-35 The booster is awesome. Only problem I have is my pump crapped out 2 weeks ago

 

[jgraz]

I was getting 2:1 waste to pure with the pump going. I was thinking of adding a second membrane since I have the housing already all I need is another membrane. I figure that should put me a right about 1:1 ratio.

Taz,
Does your pump have the pressure switch and the auto flush valve? I have both and would like to set up a float valve for my clean water bucket. If you have that, can you pls explain to me what order to plug units in and basically how to set it up. Thx

 

[Tazmaniancowboy]

I was getting 2:1 waste to pure with the pump going. I was thinking of adding a second membrane since I have the housing already all I need is another membrane. I figure that should put me a right about 1:1 ratio.

I am surprised to hear that, I have always thought and read that RO membranes usually gets 4:1. I hope it is working correctly. Did you check TDS? Also, you may not get 1:1, the problem will be that you will not be able to get the proper pressure to the second membrane if you put it inline. I do know there are ways though. I would look into the different options

Taz,
Does your pump have the pressure switch and the auto flush valve? I have both and would like to set up a float valve for my clean water bucket. If you have that, can you pls explain to me what order to plug units in and basically how to set it up. Thx

I do have the pressure switch, but do not have auto flush. If the unit has an auto shut of valve you should be able to just put the float on the end of your good water where you want it. Once that pressure backs up it should shut everything down.

 

[jgraz]

My measurement may have been a little off, I was using the lines on a bucket method. But I was getting no worse then 2.5:1. TDS measured between 51-54 going in a 0 coming out on two different meters. I was speaking with one of the guys from Ilter Guys and he suggested that I add the second membrane. also stated that it's not unusual to see increased production from 75 gpd membranes under pressure.

I do have the auto shutoff valve on the RODI system and the pressure switch. So just adding the float will automatically shut down everything when pressure backs up.

 

[Hotdogg]

Spectra pure makes some of the best RODI units and filters...Thier recommendation is between 3-1 and 4-1 (waste water to pure "0" tds)...ideal pressure should be 70psi....the colder your water the slower the process. I live in Ringwood, which has a high iron content in the water. We run between 140-180 tds going in and 0 coming out. The unit I use is capable of 90 gallons per day under ideal conditions, probably 50 -60 gallons is normal output with the cold water coming in.

 

[BuckeyeFieldSupply]

Jgraz - can't tell from your picture, but do you have it plumbed like this?

Russ

 

[BuckeyeFieldSupply]

I was getting 2:1 waste to pure with the pump going. I was thinking of adding a second membrane since I have the housing already all I need is another membrane. I figure that should put me a right about 1:1 ratio.

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,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 the membrane manufacturer. 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. 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.

Bottomline: 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 I 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?

Russ

 

[duijver]

Russ,

Thanks for the write-up.

So, in reference to forcing more water into the membrane..

I know that temperature matters, but there is probably some pressure loss while it goes through the water softener --> pre-filter --> 5 micron carbon --> 1 micron carbon --> membrane.

Given your mentioning of 50 PSI, with a 75PSI/GPD membrane, what's the max you can safely apply? I have a AWI input PSI gauge at the inbound and it's off the charts (120 i think) and I lower it to 70/80PSI. It sounds like since I already soften the water it should be less stressful on the membrane?

By the way, I replace my membrane every 2 years no matter what and change all filters every 6-8 months. We use the RO for drinking and cooking, but even with fish stuff we use about 20-30g a week of water.

 

[BuckeyeFieldSupply]

...ideal pressure should be 70psi...

I'll have to differ with you a little on this.

Different membrane manufacturers test their membrane performance under a standard (but different for many manufacturers) set of conditions including pressure and temperature. For example:

Increase your pressure for example from 40 to 70 psi, and you'll get faster permeate production. Increase to 80 and you get faster production still.

Increasing pressure also makes a huge difference in rejection (how much crud the membrane doesn't allow to pass through to the purified water), especially at the low end of the pressure range. For example:

Nothing particularly critical about 70 psi here...

Russ

 

[jgraz]

Jgraz - can't tell from your picture, but do you have it plumbed like this?

Russ

I have it plumbed in like this:
1micron pre filter
Booster
1 micron filter
Stage one of a chloromine filter
Stage two of a chloromine filter
75 GPD membrane
DI
Situated at various places are the pressure gauge, dual TDS and auto flush valve.
I have the auto pressure switch but don't use it yet as I don't have the shutoff valve yet.

 

[BuckeyeFieldSupply]

The maximum pressure for a Filmtec 75 gpd membrane is, and my guess is that this will surprise you...

21 bar or 300 psi!

The thing to remember is that all the other components in a typical RODI system aren't designed for pressure that high. The weak link in terms of being able to withstand pressure typically is the clear filter housings. So you'll see in the diagram I posted above we always recommend placing the booster pump AFTER the prefilters and just after a strainer.

80 psi is a good approach, and if you want to experiment, the components in a quality system (high likelyhood this excludes most ebay systems) starting with the RO membrane housing can handle more than 80 psi.

Are you saying your house line pressure is at 120 psi? If so, something is wrong. That should be no higher than 80 psi.

In your post you seem to be mixing operating pressure with flux & potential for the membrane to scale/foul. All these things are inter-related but distinct. It's hard to have complicated discussions via these posts so feel free to give us a call if you have questions.

Russ

 

[BuckeyeFieldSupply]

By the way, I replace my membrane every 2 years no matter what ...

My guess is that you don't need to replace your membrane this often unless you have an unusual situation.

 

[BuckeyeFieldSupply]

I have it plumbed in like this:
1micron pre filter
Booster
1 micron filter
Stage one of a chloromine filter
Stage two of a chloromine filter
75 GPD membrane
DI
Situated at various places are the pressure gauge, dual TDS and auto flush valve.
I have the auto pressure switch but don't use it yet as I don't have the shutoff valve yet.

I know you didn't ask me, but if you did
I'd have you move the booster pump after all the prefilters and after a strainer as shown in the diagram. This would avoid putting the high pumped pressure on the prefilter housings.
You might want to think about this order:

-shut off solenoid
-5 mic sediment
-1 mic sediment
-carbon block (what are the pore sizes on your two blocks? Given your 1 mic sediment filter, I wouldn't go smaller than -0.5 mic on the blocks)
-carbon block
-pressure gauge
-strainer
-pump
-RO with auto flush on the waste line
-"in" probe
-DI
-"out" probe
-pressure switch​

When you get a shut off solenoid, would be a good idea to get one that has a plug compatible with your existing wiring harness.

Russ

 

[TanksNStuff]

Russ, I'm really glad you're contributing to this thread. Many of our members will learn a great deal about how RODI systems work and how to set them up properly.

I don't want to sound like I'm arguing with you... I'm just curious to know something:

Doesn't a booster pump also increase pressure through pre filters inline before it by virtue of the suction it creates? I'm sure it's not nearly as much as if it was pushing thru them... but in order to push water faster after the pump I would think the supply to the pump will need to keep up with the demand it's pumping through the same size tubing, right?

Is that true? Or does the booster just force the existing flow through a smaller opening, thereby increasing the pressure (not actual volume)?

Thanks again for your input Russ. Looking forward to your reply.

 

[duijver]

Hi Russ,

I saw your name as a MAAST sponsor and one of their users had this same question. I somehow messed up my AWI Typhoon III RO/DI system and it is no longer producing water properly. When I setup / added in the Aquatec ERP-1000 permeate pump I think I tinkered with the cables and now I think it's bypassing the membrane. Do you have a screenshot showing the permeate pump as part of the setup?

My RO and RO/DI are working,sort of, but the RO/DI is taking the 133 TDS down to 50-55 TDS and before I took off the DI stage and I was getting 15 from the RO+PH stablizer unit. So, something is really messed up.

Thanks!