RO - Membranes

[rshiggaon]

Hello: I am currently using KR membranes https://www.kleen-ritecorp.com/p-44539-kleen-rite-reverse-osmosis-membrane-4-x-40-inches-2500-gpd.aspx two of them on my JC unit. I end up replacing them every year, and my TDS meter is currently reading 85 ppm (due for change). I have a few questions and looking for advice from more experienced people here:

1. How long do your membranes typically last? I understand this depends on usage, but I don't have a good way to measure it. I have 5 SS Bays and 1 soft touch auto wash.
2. How do I test carbon filter is doing its job or needs service? (Carbon Filter -> Sediment Filter -> RO)
3. What is the best membrane you recommend?

Additional details:

• I replace my pre-sediment filter every 3 months.
• I have backwash the carbon filter, which hasn't been serviced for 5 years (as per the seller).
• There is no water softener installed. The seller mentioned it was removed, and the water hardness tested at 6 grains per gallon.

Thank you.

 

[OurTown]

Our membranes seemed to last many years. I think you need a softener to make the membranes last longer. You can get a chlorine test kit and it is best to test the reject water while it is running to make sure the carbon is still good.

 

[rshiggaon]

Our membranes seemed to last many years. I think you need a softener to make the membranes last longer. You can get a chlorine test kit and it is best to test the reject water while it is running to make sure the carbon is still good.

Thank you, reject water from the RO, right? Also, what chlorine levels should I look for that indicate it needs a service?

 

[OurTown]

Thank you, reject water from the RO, right? Also, what chlorine levels should I look for that indicate it needs a service?

Yes, reject from the RO. From what I understand any detectable chlorine level is bad for the membranes and the carbon would need to be changed out.

 

[AnalyticWash]

6 grains of hardness and no softener...you should invest in getting one.

 

[Buckeye Hydro]

You should be getting more than a year out of your membranes. The use-able lifespan of the membranes is most affected by your pretreatment - what you do to the feedwater before it reaches the membrane.

In your case:

• Contact your water utility and see what they use as a disinfectant. It will either be a form of chlorine, or it will be chloramine (chlorine + ammonia). The answer to this question will have a big effect on the appropriate size of your backwashing carbon tank, and on the type of carbon to use. At 5 years of age you're near or at the time to replace the media in this tank. Test your concentrate for chlorine as OurTown mentioned. Chloramine will show up as Total Chlorine. Chlorine will show up as Free Chlorine. Although often not used in the carwash world, a lockout switch on the carbon tank is a great idea and is widely/typically/commonly used in other business types.
• At 6 gpg hardness, as mentioned above, you need a softener. Just like hard water deposits scale on your plumbing fixtures, it will deposit scale inside your RO membranes. The scale will plug the membrane (slowing down the production of purified water), and it will create small holes in the membrane and cause higher TDS in the permeate (like you're seeing now). What is the TDS of your feedwater? Depending upon the operation of your wash, you may or may not want a twin tank alternating softener rather than a single tank softener. We can talk in detail about this if you'd like. If you're going to get a softener do yourself a favor and use one with a Clack brand valve. You'll thank me when it comes time for maintenance on the valve!

The life you get out of your membranes will also be affected by the way you have your system set - typically on a commercial RO you have at least two flow gauges - one for the permeate (RO water) and one for the concentrate (flush water or "waste" water). The concentrate flow can be adjusted - and changing this flow will affect your "pump out" pressure and your permeate flow. You may also have a gauge and needle valve for a recycle function. If you do... because you do not have a softener, you should not be recycling any of your concentrate.

To suggest a replacement 4040 membrane (this means a membrane that is 4" in diameter and 40 inches long, nominal) for you, we would look at these settings on your RO system, have you adjust if needed, and look at your feedwater temperature, and then look at the lowest energy (pressure) membrane that will do the job for you.

Russ

 

[OurTown]

Although often not used in the carwash world, a lockout switch on the carbon tank is a great idea and is widely/typically/commonly used in other business types.

What is this?

 

[Buckeye Hydro]

This is a microswitch installed on the carbon tank valve. A two conductor cable runs from the switch to the RO, and signals the RO to shut off if it is running when the carbon tank goes into backwash. This is especially useful if there is a high likelihood of the RO running when you have the carbon tank set to backwash (often the default is set at 2 AM). Without this control the RO will be fed by chlorinated (or chloraminated) water.

Russ

 

[water guy]

What switch are you talking about on the RO?

 

[Buckeye Hydro]

Better quality RO systems will come with a coiled up cable with bare wire leads labeled "prefiltration" or something like that for this purpose. Or some will have contacts on the controller where these switch wires can be connected. Check your manual.

If none of those things exist, we install an "RO Control Module" that we build here that has a few functions:

• allows tether float switch in storage tank to control the current going to the RO
• allows the prefilter lockout switch to control the current going to the RO
• as a safety feature runs only low voltage (12 volts) into the storage tank tether float switch

Russ

 

[Rudy]

I'm not sure I'm reading this thread correctly.

You want to do a chlorine test AFTER the carbon filter, and before entering the RO system. Chlorine murders the membranes.

At our wash, we do a chlorine test (a swimming pool test kit works for us) monthly. We have great incoming water, and I usually need to replace the carbon every 5 years or so. At the first hint of ANY chlorine getting past the carbon filter....the RO goes off, and the carbon gets replaced.

Ditto what Buckeye says about having a carbon filter bypass shutoff.

You don't want chlorinated water getting to the RO during the Carbon filter's backwashing cycle. You need something that prevents the RO from coming on during the backwash cycle.

We get years, and years out of our membranes......probably 5years+. (And yes, we use softened water with ZERO grains of hardness going to the RO).

 

[Axxlrod]

I'm due for some new membranes? Where's the best place to buy from online? Any other sources than KR?

 

[Rudy]

I've purchased XLE (Extra Low Energy) 4040 Membranes from Coastal Water Filters on eBay with good success. I run them between 80-100psi (depends on time of year). Right now, they're about $175.

I have ZERO affiliation with them. I'm just a satisfied customer.

 

[Fatboy769]

I'm due for some new membranes? Where's the best place to buy from online? Any other sources than KR?

What about @Buckeye Hydro

 

[rshiggaon]

You should be getting more than a year out of your membranes. The use-able lifespan of the membranes is most affected by your pretreatment - what you do to the feedwater before it reaches the membrane.

In your case:

• Contact your water utility and see what they use as a disinfectant. It will either be a form of chlorine, or it will be chloramine (chlorine + ammonia). The answer to this question will have a big effect on the appropriate size of your backwashing carbon tank, and on the type of carbon to use. At 5 years of age you're near or at the time to replace the media in this tank. Test your concentrate for chlorine as OurTown mentioned. Chloramine will show up as Total Chlorine. Chlorine will show up as Free Chlorine. Although often not used in the carwash world, a lockout switch on the carbon tank is a great idea and is widely/typically/commonly used in other business types.
• At 6 gpg hardness, as mentioned above, you need a softener. Just like hard water deposits scale on your plumbing fixtures, it will deposit scale inside your RO membranes. The scale will plug the membrane (slowing down the production of purified water), and it will create small holes in the membrane and cause higher TDS in the permeate (like you're seeing now). What is the TDS of your feedwater? Depending upon the operation of your wash, you may or may not want a twin tank alternating softener rather than a single tank softener. We can talk in detail about this if you'd like. If you're going to get a softener do yourself a favor and use one with a Clack brand valve. You'll thank me when it comes time for maintenance on the valve!

The life you get out of your membranes will also be affected by the way you have your system set - typically on a commercial RO you have at least two flow gauges - one for the permeate (RO water) and one for the concentrate (flush water or "waste" water). The concentrate flow can be adjusted - and changing this flow will affect your "pump out" pressure and your permeate flow. You may also have a gauge and needle valve for a recycle function. If you do... because you do not have a softener, you should not be recycling any of your concentrate.

To suggest a replacement 4040 membrane (this means a membrane that is 4" in diameter and 40 inches long, nominal) for you, we would look at these settings on your RO system, have you adjust if needed, and look at your feedwater temperature, and then look at the lowest energy (pressure) membrane that will do the job for you.

Russ

This message contains a lot of useful information, and I've learned quite a bit. I realize that I need to invest in a water softener and replace the media in my carbon tank. I also plan to measure the chlorine levels.

Currently, the RO water measures around 280 TDS, but I haven't measured my city feed water yet. I have a recycle function and do recycle some of the reject water. Based on your comments, it seems I shouldn't be doing that. I also keep 1.5 gallons of RO water and 3 gallons of reject water, maintaining a 2:1 ratio of reject water to RO water.

I have the Jim Coleman RO System, but I need to figure out carbon filter bypass shuts off.

I'll reach out to you to discuss my setup in more detail and get some suggestions.

 

[rshiggaon]

I've purchased XLE (Extra Low Energy) 4040 Membranes from Coastal Water Filters on eBay with good success. I run them between 80-100psi (depends on time of year). Right now, they're about $175.

I have ZERO affiliation with them. I'm just a satisfied customer.

Is this the one that you are talking about Ozmosis XLE-4040 Reverse Osmosis RO Membrane for Water Filtration System 4"x40" ?

 

[Rudy]

Yes.

It's worked very well for me in my Applied Membranes system.

Again, I'm NOT associated with the eBay seller in any way, except that I've been very pleased with the price and performance of this membrane.

 

[OurTown]

Currently, the RO water measures around 280 TDS

I thought you said it was 85 but was due for a membrane change out. What is the TDS typically right after a membrane change? It is possible to start leaving spots on black cars with anything over 25 TDS.

 

[rshiggaon]

I thought you said it was 85 but was due for a membrane change out. What is the TDS typically right after a membrane change? It is possible to start leaving spots on black cars with anything over 25 TDS.

Sorry, I was not clear. TDS for the RO water is 85 and the TDS for the pretreatment water which is an input to the membranes is 280 (Coming out of the Carbon + Sediment filter).

Yes I am seeing the spots right now.

 

[Buckeye Hydro]

Sorry, I was not clear. TDS for the RO water is 85 and the TDS for the pretreatment water which is an input to the membranes is 280 (Coming out of the Carbon + Sediment filter).

Yes I am seeing the spots right now.

So here's some early morning jargon and math for you.
If your Feedwater is 280 ppm,
and your permeate (RO water) is 85 ppm,
then your rejection rate is
1 - (85/280) =
1 - (0.30) =
0.70, or 70%

You want the rejection rate to be something north of 95% - meaning the membranes would be rejecting 95+% of the total dissolved solids in the feedwater.

Always measure the TDS in the permeate after you let the system run for a few minutes.
Don't measure the permeate TDS from a holding tank.

Russ