RO/DI Question - RO Membranes in Series

[coralcrazy]

I have very high tds in my area. I am burning through DI resin and even when the DI resin is half exhausted I have 2-3 TDS. I am wondering If I could run a dual membrane system with the clean output of one membrane being the input to another? I can then run a dual waste water system with both membranes having a flow restrictor. Will this work?

TDS at 500ppm going in.

I am using a BRS 75 god RO/DI system.

Thanks-

 

[Jimbo662]

I just upgraded my BRS 75g unit to 150g with their upgrade kit which adds the 2nd membrane. It's a very quick / easy process. They've got a video on the page to show how to hook it up.

150 GPD Water Saving Upgrade Kit - Bulk Reef Supply

 

[AZDesertRat]

The dual membrane systems you see all send the waste from the first membrane into the second membrane to increase the GPD, not to save water or further treat the water.
What you describe would require a booster pump since the water exiting the first membrane would be basically at atmospheric pressure and would have to be repressurized to get it through the second.
Do not believe the water saving some vendors claim, dual membranes are not water savers and will fail prematurely if not kept well flushed, this has been demonstarted many times by vendors with much more experience. Note none of the long time vendors, those with say 15+ years in the industry make this claim, they all know better. When you send the concentrated brine from one membrane into a second membrane it is even more important to keep the waste ratio up or both membranes suffer a shortened life driving the cost of ownership up. Dual membranes are to increase production, not to reduce waste.

Membranes are not all the same and some are much better than others. My tap water TDS varies between 550 and 850 and my RO only TDS varies between 2 and 3 always with DI lasting over 1000 gallons per cartridge. You can buy a hand tested 90 GPD RO membrane guaranteed to be 99% rejection rate for only $55 here:
NEW 99 Percent Rejection SpectraSelect Plus? 90-GPD RO Membrane

Here is an article documenting what that 99% means to you:
FAQ p.2

A few questions, what is your tap water TDS? Do you know your water hardness or do you have a water softener? What is your water pressure and water temperature? What is your exact measured waste ratio? Do you have CO2 in your water or if you don't know try using this nomograph to measure it, CO2 eats DI regardless of the TDS.
FAQ

 

[joekool]

You need a booster pump and run pressure at 100psi you will get 99% rejection at that rate. 500is not that bad but your rejection rate is no good. Tell us your setup like what filters in what stages, how old your membrane is and what psi you are getting currently at your membrane. Most membranes will only do 95% at 60psi.

You can call aquafx and talk to Pete he is really nice and will talk you through what you need to do. I got a great deal on a booster pump from them as well.

 

[coralcrazy]

The dual membrane systems you see all send the waste from the first membrane into the second membrane to increase the GPD, not to save water or further treat the water.
What you describe would require a booster pump since the water exiting the first membrane would be basically at atmospheric pressure and would have to be repressurized to get it through the second.
Do not believe the water saving some vendors claim, dual membranes are not water savers and will fail prematurely if not kept well flushed, this has been demonstarted many times by vendors with much more experience. Note none of the long time vendors, those with say 15+ years in the industry make this claim, they all know better. When you send the concentrated brine from one membrane into a second membrane it is even more important to keep the waste ratio up or both membranes suffer a shortened life driving the cost of ownership up. Dual membranes are to increase production, not to reduce waste.

Membranes are not all the same and some are much better than others. My tap water TDS varies between 550 and 850 and my RO only TDS varies between 2 and 3 always with DI lasting over 1000 gallons per cartridge. You can buy a hand tested 90 GPD RO membrane guaranteed to be 99% rejection rate for only $55 here:
NEW 99 Percent Rejection SpectraSelect Plus? 90-GPD RO Membrane

Here is an article documenting what that 99% means to you:
FAQ p.2

A few questions, what is your tap water TDS? Do you know your water hardness or do you have a water softener? What is your water pressure and water temperature? What is your exact measured waste ratio? Do you have CO2 in your water or if you don't know try using this nomograph to measure it, CO2 eats DI regardless of the TDS.
FAQ

Tap water TDS is 500ppm

I have very hard water, I have a water softener but the RO is in the garage attached before the softner. I adjusted the pressure on the house to 65 psi which is about 10 feet away from the ro feed. Temperature probably fluctuates from 70 - 85 in the garage (I live in orange county, ca). I do not know my waste water ratio nor do I know about the presence of Co2.

 

[coralcrazy]

You need a booster pump and run pressure at 100psi you will get 99% rejection at that rate. 500is not that bad but your rejection rate is no good. Tell us your setup like what filters in what stages, how old your membrane is and what psi you are getting currently at your membrane. Most membranes will only do 95% at 60psi.

You can call aquafx and talk to Pete he is really nice and will talk you through what you need to do. I got a great deal on a booster pump from them as well.

I have a BRS 5 Stage 75 gpd system. It is about a month old. PSI to house is 65 (I can adjust), the ro unit is about 10 feet away from that in the garage.

 

[AZDesertRat]

The absolute best thing you can do for your RO/DI is use softened water.Membranes love soft water as it does much of the work for them. The other is increase the pressure if you have that option, the higher the pressure the better the membrane functions, I run mine at 100 psi to get 99.43% rejection rate, but I also have a Spectrapure 99% guaranteed membrane too which makes a world of difference.
What is your rejection rate now, you need your tap water TDS and RO only TDS before the DI to calculate this.
Measure your waste ratio using a measuring cup and clock or watch. Measure the waste for one minute then measure the treated flow for one minute and tell us the ounces or milliliters from each.

 

[coralcrazy]

The absolute best thing you can do for your RO/DI is use softened water.Membranes love soft water as it does much of the work for them. The other is increase the pressure if you have that option, the higher the pressure the better the membrane functions, I run mine at 100 psi to get 99.43% rejection rate, but I also have a Spectrapure 99% guaranteed membrane too which makes a world of difference.
What is your rejection rate now, you need your tap water TDS and RO only TDS before the DI to calculate this.
Measure your waste ratio using a measuring cup and clock or watch. Measure the waste for one minute then measure the treated flow for one minute and tell us the ounces or milliliters from each.

I'll check the waste water ration when I get home and update. I think I will also purchase a pressure guage to measure at the membrane. I do have the option to up my water pressure on my house as a whole.

 

[coralcrazy]

This would work for a pressure gauge right?

Gauge

Adapter

 

[AZDesertRat]

I would look at something more like this for an RO application.
Pressure Gauge Kit w/ 1/4in push fittings

Or this
http://www.amazon.com/Stainless-Pre...=1400704794&sr=1-1&keywords=RO+pressure+gauge

Both have all plastic tees so no metals to be eaten up and both use stainless steel gauges so no copper or brass. I prefer the back mount gauge like the Spectrapure but either will work the same. Also they are both 0-160 psi which most manufacturers recommend your operating pressure should be in the middle band of the gauge range so say 70-90 psi would be in the middle. A slight water hammer could peg the 0-100 and damage it permanently.

 

[dereks16]

I have an installation question for an RODI float switch. My RODI is under my sink in the kitchen. I pull my 20 Gallon brute from the living to the kitchen to fill. My problem is installing the float for auto shut off purposes means I can't take it back and forth. Is there an easIER connector that I can put outside the barrel on the product line so I can connect and disconnect each time? Or a different idea for installing

 

[coralcrazy]

I have an installation question for an RODI float switch. My RODI is under my sink in the kitchen. I pull my 20 Gallon brute from the living to the kitchen to fill. My problem is installing the float for auto shut off purposes means I can't take it back and forth. Is there an easIER connector that I can put outside the barrel on the product line so I can connect and disconnect each time? Or a different idea for installing

Put a ball valve on the outside of the trashcan connected to float valve.

 

[joekool]

I just use the nut that screws the line to the male side of the float switch. Screw it on use it screw it off. I'll take a picture later to show you.

 

[dereks16]

Don't those ball valves have the connectors where when you pull the line it tightens. Those are a pain. Is there a quicker disconnect than that?

 

[dereks16]

Joe I was thinking that myself but worry about the little pieces inside. I'll do what I have to but looking for other options too. Send the pictures when you can love to see

 

[blufin]

I tried to "band aid" a drinking water RO system system to make it function for what I needed for aquarium duty. It never worked. I scraped it and took AZ 'Rats advice and went with a spectrapure system. I couldn't be happier with the results. My incoming TDS is 650+. The TDS out of the membrane is only 3-4, and the resin/DI take care of the rest. Perfect water every time. I used a full DI resin cartridge to make 5-6 gallons with the old system.
I highly recommend you follow the advice of the 'Rat. He knows his stuff.
Thanks 'Rat.

 

[AZDesertRat]

I like the ball valve advice as a quick disconnect for a float valve installed in a trash can or bucket. The John Guest style quick fittings are a breeze to connect and disconnect, all you have to do is depress the lok ring and the tubing slips right out.

 

[dereks16]

John guest? Do you happen to have something I can look at? If it's different than the one I have I'll give it a shot. But the one I have I mentioned. Before is a pain and not so quick on the quick release.

 

[dereks16]

And is the ball valve idea that different from the nut that connects the RODI hose to the float valve?

 

[AZDesertRat]

Old style compression nuts are a pain and do not stand up well to movement like the quick fittings do.

This is a speed fittting, probably the same thing you were referring to but they are simple to take apart by pushing in on the lock ring while pulling the tubing out.
John Guest - The World Leader in Push-fit Fittings, Pipe and Plastic Plumbing Systems - speedfit technology

The only time when they are hard to take apart is when they are under pressure. If you disconnect it on the float valve side after shutting the ball valve off and raising the float once manually to relieve pressure it should be no problem at all.