RO System

[Joswhaha]

Howdy Yall,
So my RO water is about 70 hardness and I am going to work to correct the issue. I had Culligan come rebuild my carbon filter and they are supposed to come back and repair the RO system but due to Covid they are way backed up. My incoming water is about 400 and the water going to my storage tank is around 74. I have looked for diagrams about how this system is supposed to work but haven’t found anything yet.

My main question is what the heck is this reject water and where does it go? It looks like the water comes through the filter to remove the chlorine -to a sediment filter -to a medium pressure pump - to a 40” membrane then another membrane then to the holding tank. I’ve got a valve that is turned off that may be what the reject water is supposed to be, I had to replace the valve today as it was leaking but it is a ball valve for the time being.

I will take pictures tomorrow.

 

[MEP001]

Did you notice the huge crack in the PVC fitting to the left of the ball valve?

I assume your TDS is reading 70. If your RO water is actually testing 70 hardness, your system is way beyond screwed.

RO systems are surprisingly simple. Culligan is going to charge yo a small fortune to fix your system. It's pretty much as you said above: carbon prefilter to remove chlorine, prefilter to catch sefiment including carbon from the filter, them it's pumped through membranes. The permeate should free-flow unrestricted to storage, and there needs to be something to regulate the system pressure. A ball valve works well, it's just not particularly accurate. I like to use a low-pressure regulator to control system pressure with a valve to control the flow to reject. With the increase in flow through the membranes you also get a higher production and you can reduce the reject to 1:1 of product. A lot of older systems dump 3-4 parts down the drain for every 1 part product. The rest is safety like low inlet pressure shutoff.

 

[Joswhaha]

Yeah, that picture was actually of the broken fitting but I only had those 2 pictures on my phone. I had to replace the fitting and valve due to a little leakage.

I am going to try to spend a few minutes tomorrow figuring this out and save me from paying a ridiculous price to get it working.

I can order some new membranes but are there other parts I should replace at the same time? How do I know how much reject water there should be? I’m thinking there is zero now going to the reject( looks like the reject goes to my self serve water storage tank)

 

[Joswhaha]

As far as water quality my TDS is in the 70s after the RO. My hardness from the city is about 6 and now that the softener is actually plugged in and mostly operational is low. I cannot remember exactly though. I only have the soap test and I test the water every time I’m there because I have to manually start the softener due to a bad flow meter(I think)

I ordered a TDS and a good water hardness tester but they haven’t shown up yet.

 

[MEP001]

Can you get rid of the pressurized storage tank? That would clear out a lot of space and remove what looks a lot like a complicated mess. I see what I assume is a storage tank to the left. Is the pressurized tank used to deliver spot free water to something?

The rest of the unit looks like a plumbing nightmare, and it doesn't have to be. I'd replumb it with 1/2" hose to get the volume (I doubt the 1/2" OD tubing is sufficient). If you replumb it to have all the pumped water flow through both membranes and tee a part of the reject back to the pump inlet, you should get roughly 2 GPM on both product and reject flowmeters.

 

[Joswhaha]

Yes, that pressure tank is disconnected, it was for a water filling station that is no longer in use.

Where does the reject water come from? Is the reject from the bottom of the 2nd membrane the water passes through? There is a tee there with one line going to the storage tank and one back to just past the pump inlet with a couple of valves.

On the 2 flow meters while running I get zero flow through the second I’m guessing that’s the reject water and I get over 5 through the tank meter.

 

[water guy]

You may want to take all that stuff out and start new .Finding a culligan rep with a enough knowledge to work on it maybe a challenge and also very expensive

 

[chaz]

Sounds like your carbon System has been recently serviced. Now make sure the pre filter is new and then the membranes. Many washes use the reject water in ss or presoak functions. id also test the TDS as it enters the storage tank. on my system…there’s a ball valve that is normally OFF, used only for priming….that may be the case for the valve u replaced?

 

[Joswhaha]

Thanks guys, I have been working on this a little today and it appears pretty straight forward. It looks like the reject water tees into 2 valves, one that sends the reject back through the membranes and one that sends the reject out of the system. The valve that sends the water out of the RO system(to the SS tank in my case) was closed and the valve to send the water back to the membranes was open.

Sounds like I need to adjust this to allow the reject water to leave the system at about the same rate as I send water to my holding tank. I’m going to continue to work with it till I get a solid grasp on what it takes to get good spot free water.

 

[Joswhaha]

Alrighty, I think I got the valves adjusted and everything operational. I just need to order new membranes and replumb this setup with 1/2”. Currently, it looks like I am getting 1 maybe 1.5 gallons per minute through the flow meter.

Do you guys have recommendations on new membranes? Should I get ones that can handle some chlorine?

 

[Greg Pack]

If you've changed the charcoal you're likely good for several Years.

I've used some less expensive membranes(around $200) with reasonable luck, but have historically used Dow filmtec which are around $300 each

 

[mjwalsh]

Do you guys have recommendations on new membranes? Should I get ones that can handle some chlorine?

Specialty Equip way back in 1987 installed a chlorine resistant system. We have a cellulose acetate RO membrane. The good news is no need for carbon. The bad news is that we are forced to maintain an acid pre-treatment. Hopefully, I have gathered enough info here on the forum to transition to a charcoal filter pre-treatment. Another advantage to the TFC membrane I have noticed is the lower replacement price for the 4 x 40 size.

The following has good reviews. Any thoughts? ....

https://www.amazon.com/Hydronix-BW-4040-Performance-Commercial-Industrial/dp/B01CFOGPXY/ref=sr_1_9?keywords=Reverse+Osmosis+Membranes&qid=1644512218&sr=8-9

 

[MEP001]

If you've changed the charcoal you're likely good for several Years.

I've used some less expensive membranes(around $200) with reasonable luck, but have historically used Dow filmtec which are around $300 each

Same, with the charcoal filter if it's 1 cu.ft. per membrane the charcoal will outlast the membrane. I change both together.

 

[chaz]

Not sure why you’d send any reject back to the RO system. Reject is just that ….in my case to storage tank for SS with any overflow from there going to waste. I asa the valve back to RO is for initial priming…at least in mine it is

 

[MEP001]

Not sure why you’d send any reject back to the RO system. Reject is just that ….in my case to storage tank for SS with any overflow from there going to waste. I asa the valve back to RO is for initial priming…at least in mine it is

That's how reverse osmosis works. The higher flow through the membranes keeps them from fouling, and it increases the production with no cost. You can run 1:1 reject/product at the higher flow, where if none gets recirculated you need to run at least 3:1 reject just to get a decent life out of the membranes. I've been doing service work on some of the same car washes for 30 years, and they get up to ten years out of their membranes with a portion of the reject returned to the pump.

 

[chaz]

That's how reverse osmosis works. The higher flow through the membranes keeps them from fouling, and it increases the production with no cost. You can run 1:1 reject/product at the higher flow, where if none gets recirculated you need to run at least 3:1 reject just to get a decent life out of the membranes. I've been doing service work on some of the same car washes for 30 years, and they get up to ten years out of their membranes with a portion of the reject returned to the pump.

ah! Tks

 

[Joswhaha]

So after adjusting these valves and letting the machine do it’s job for a couple of days, the TDS is now reading about 30. It was around 70 before the minor adjustments. Does anyone know at what TDS water spots are bad? I have some new membranes ordered and assume it will take care of everything.

 

[MEP001]

30 TDS is borderline. Some manufacturers say 50 is the threshold, but my test is to clean the windows well enough that water beads on them, spray spot free rinse on them and let it dry in the sun. At 50 it will spot, at 30 it's not noticeable.

 

[Joswhaha]

I will do a little testing to see if I get spots. I’m a little surprised that adjusting those valves did so much to change the TDS. I may repipe it now, do you think I will get more production out of the setup with 1/2” id tubing? I get about 1 gallon per minute and I do not run out with the 300 gallon tank. Do I guess I don’t need to worry about it to much.

 

[MEP001]

do you think I will get more production out of the setup with 1/2” id tubing?

I can't say for sure, 1/2" OD tubing seems too small to me, but it's probably sufficient flow at 200 PSI. It might take some strain off the pump, but it probably won't significantly change the production.