ro/di running slow

[pappasmurf]

I have a 90gpd system going into a 50gal container. It is taking about 2 days to fill it up. Do the lines clog? Anyone have any suggestions. Tim

[Reefdiver72]

Have you looked at your wste hose to make sure your not losing water all your water out of it thats what happened when my filter went bad.

[haggarse]

Have you checked the pressure gauge? Maybe there is a PSI issue?

[ReefFreaks]

My guess would be the recent drop in water temp. Cold water expands making it tougher to pass through the membrane. Options....a booster/pressure pump, pre WARM the water prior to it going to the RO, move to a warm climate

[asm481]

get the pressure pump.

[szwab]

how old are the prefilters. first and cheapest step would be to change those out.
how old is the membrane?

[itZme]

I would guess the water feed temp also. I have a 50 gpd Kent Maxxima system and I took 100ft of RO tubing and put it inline before the RO system. I placed the tubing into my sump where it is submerged in 78 degree water and it warms the input water to roughly 78 degrees before passing through the RO system. Before doing this I would get considerably less output water per day. Now I can calculate how long it needs to run by dividing the 50gpd by 24hrs and it is almost exactly correct. The OPTIMAL temp for reverse osmosis input water is 77 degrees F. The optimal pressure is 65 PSI. If you have anywhere close to 65 PSI do not increase the pressure by using a pump or you will defeat the purpose of an RO system by forcing impurities through the membrane.

Here is some info I posted before on C-SEA about the same problem.

"The performance of a system depends on factors such as membrane type, flow control, feed water quality, temperature and pressure. Also only part of the water entering the unit is useable, this is called the % recovery. This is affected by the factors listed above. For example the amount of treated water produced can decrease by about 1-2% for every 1 degree Celsius below the optimum temperature."

So if your ground water temp is now 50 since it is cold outside and the optimal temp is 77 that makes the difference 27 degrees F. That translates to a difference of 15 C. You can be losing 15-30% efficiency just by feeding 50 degree water. I know that my water gets even colder than that sometimes in winter.

Fosters&Smith says to shoot for 70-77 degrees. BFS says 77 is perfect. Other sites I have visited all agree on 77 so thats what I aim for. If you can't pre-heat the water in your sump you could look into doing this in a 5g bucket with a small heater or just getting a faucet adapter and using your house's hot water to blend with the cold to get closer to 77.

Hope that helps.
-- Kevin

[BuckeyeFS]

We have a calculator on our website where you can input the water temperature and water pressure and see what your membrane ought to produce under those conditions.

Russ

[BuckeyeFS]

Originally posted by itZme
I would guess the water feed temp also. I have a 50 gpd Kent Maxxima system and I took 100ft of RO tubing and put it inline before the RO system. I placed the tubing into my sump where it is submerged in 78 degree water and it warms the input water to roughly 78 degrees before passing through the RO system. Before doing this I would get considerably less output water per day. Now I can calculate how long it needs to run by dividing the 50gpd by 24hrs and it is almost exactly correct. The OPTIMAL temp for reverse osmosis input water is 77 degrees F. The optimal pressure is 65 PSI. If you have anywhere close to 65 PSI do not increase the pressure by using a pump or you will defeat the purpose of an RO system by forcing impurities through the membrane.

-- Kevin

Filmtec membranes are spec'ed at 77 degrees and 50 psi. Higher pressure is better - 65 is good, 75 is better, up to about 90 psi where you start to approach max pressure limits for components in your system other than the membrane.

The problem with using 100 feet of tubing in a warm water bath is that you'll lose pressure because of the long tubing run.

Russ

[itZme]

Originally posted by BuckeyeFS
The problem with using 100 feet of tubing in a warm water bath is that you'll lose pressure because of the long tubing run.

Russ

Good to know. I will have to put a gauge on it sometime and see what pressure I have. I have it directly plumbed into a 3/4" copper line just about 8 ft above my tanks. Thanks for the info... always good to see you, with your knowledge, chime in on the RO/DI discussions

[RokleM]

Originally posted by BuckeyeFS
Filmtec membranes are spec'ed at 77 degrees and 50 psi. Higher pressure is better - 65 is good, 75 is better, up to about 90 psi where you start to approach max pressure limits for components in your system other than the membrane.

The problem with using 100 feet of tubing in a warm water bath is that you'll lose pressure because of the long tubing run.

Russ

So even though they're rated for 50 you can run them higher? I need to crank up my pump because it boosts me up to about 55 PSI. Is 75 a good number to shoot for then?

[BuckeyeFS]

Eric - if you have a booster pump, shoot for 85 to 90 psi.

Russ

[RokleM]

Originally posted by BuckeyeFS
Eric - if you have a booster pump, shoot for 85 to 90 psi.

Russ

I do indeed (and 75gpd Filmtec), good to know. Hilliard's water pressure is extremely pathetic (35 PSI), so I got a booster from you guys to push it to 55. Looking at the calculator, going from 55 to 80 will make QUITE a difference.

Sorry to interrupt the thread. You learn something every time Russ chimes in on a thread

BTW, I tried the heat trick last year as well, and it worked decently. I had about 25-50' of hose in a Kent salt bucket with a 300w heater. That was before the booster pump though. If my performance jumps as much as the calculator shows, I won't bother with the bucket this winter.

[BuckeyeFS]

Yes - the booster pumps seem to surprise people in the difference in production they see.

Russ

[TOURKID]

Russ, i have been wanting to ask someone. I have a spectrapure three stage ro di. the middle one goes fast due to clorines (right?) does well water have clorine? Im noticeing my 1st getting dirty fastest, and my colorchanging di was really nasty after 2 months (40 tds after changing the other two filters)

[BuckeyeFS]

Did you mean a 4 stage? Across the bottom you have a sediment filter, a carbon block, and a DI cartridge, right? If so, that makes 3, and then the RO membrane across the top of the bracket would =4 stages.

So the stage in the middle would be a carbon block. If you have a sediment filter with the correct pore size ahead of the block, and if the block has a high "chlorine capacity," it shouldn't need to be replaced too often, no.

Well water straight from the well wouldn't (shouldn't) contain chlorine, but it is not uncommon for whole house drinking water systems to include chlorine injection - I don't know if that is your situation or not - if it was you would know it. The carbon stage also removes other VOC's - the list of VOC's reads like a list of difficult to pronounce chemical nasties - intuitively you'd look at the list and say that you'd not want them in your tank. So even if you don't inject chlorine into your well water as part of a whole-house treatment system, don't remove the carbon block from your RODI system.

So you are seeing your sediment filter load up fast? The good news is that means that the filter is doing what you asked it to - it is catching the sediment in the feedwater. The bad news is that if the sediment filter (and your carbon block and any other prefilters) starts to clog, it will rob pressure from the RO membrane and your system won't perform as well as it should (or at all). You have a few options. 1. Simply change your sediment filter more often - keep an eye on your pressure gauge to tell you when the filter is starting to clog. 2. Add another sediment filter in front of your RODI system with a bit larger pore size that your existing sediment filter. 3. Add a whole-house filter (essentially a large capacity sediment filter).

With heavy sediment loads use what is called a depth (sediment) filter. These filters have multiple layers - each layer has a smaller pore size as you move from the outside of the filter towards the inside. Sounds expensive but that's not the case. Our depth filters are just a tad more expensive than our standard sediment filters.

If you are burning through DI resin quickly, the culprit may be a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker then would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). Filmtec 75 gpd (and below) membranes produce less purified water (a.k.a. “permeate”), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependant upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, use your tds meter to measure the total dissolved solids (TDS) in the feedwater (that is, your tap water), and in the purified water (permeate) produced by the membrane (not your DI water). Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new.

If there's a problem with low rejection, sometimes its an easy/free fix, and sometimes its an indication that the membrane and/or other parts in the system need to be replaced.

What is your waste to permeate ratio?

Russ

[pappasmurf]

Thanks for all the info. The filters are all new ( changed a month ago ) . Membrane is only about 4 months old.
Never heard about adding a pressure pump before, where can I get one ( how big of a pressure pump do I need ), and where do you hook it up? Right now I am coming out of a 1/2" cold line with shutoff valve. I keep the psi guage on the ro system at 80.
Tim

[BuckeyeFS]

Originally posted by pappasmurf
Thanks for all the info. The filters are all new ( changed a month ago ) . Membrane is only about 4 months old.
Never heard about adding a pressure pump before, where can I get one ( how big of a pressure pump do I need ), and where do you hook it up? Right now I am coming out of a 1/2" cold line with shutoff valve. I keep the psi guage on the ro system at 80.
Tim

How do you keep the pressure gauge at 80? With an adjustable flow restrictor?

What is your waste to permeate ratio?

I sent you a PM with a reference to our booster pumps.

Russ

[BuckeyeFS]

Booster pumps go in-line prior to the membrane. They are adjustable so you can set the pressure where you'd like.

Russ

[pappasmurf]

Russ, pm sent

[MarineFishGuy]

Interesting comments Russ, thanks for the info.
I am getting ready to order a new 75gpd Membrane (to replace my 50) and the dual inline meter from your website. I PMed you what I plan on ordering.

My Numbers:
Feed Water: 358
After 1 micron sediment filter and Carbon block filter: 422
After RO Membrane: 63
After DI Resin: 0
In Holding tank: 3
Feed Pressure: 38psi
Feed Temp: 62.5 Degrees F

From your calculator it looks like I can expect 28gpd production.

Does the fact that my PPM is higher after my first two stages mean I need to replace those filters? (My guess is yes)
At first I thought it was a mistake so I measured all of my sources again.
I used the same glass and dried it between each reading. The readings were within 5ppm for each run.

It appears my RO Membrane is working at 85% rejection rate (correct?)
I did not measure it in this way when it was new, so I don't have a basis for comparison.
Even though my product water is 0 tds, it looks like I should replace my RO Membrane, correct?
Thanks,
Ken

[BuckeyeFS]

You are seeing an 82% rejection - that's pretty poor. Before you buy a new membrane - did you let the system run for a about 10 minutes before you took these measurements?

I suspect the higher reading after your prefilters is an artifact of the way you measured the tds - unless your prefilters are really nasty.